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Development and study of fully biodegradable composite materials based on poly(butylene succinate) and hemp fibers or hemp shives
Abstract
The use of natural fibers to reinforce polymers is an established practice, and biocomposites have gained an increased interest in areas such as automotive, construction, and agriculture. The purpose of the present work was the preparation and study of fully biodegradable (“green”) composite materials using poly(butylene succinate) (PBSu) as polymeric matrix and hemp fibers and shives as fillers. Composites containing 15, 30, 50, 60, and 70 wt% of fillers were prepared by melt mixing in a twin screw extruder. The composites were studied using Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimeter while the dispersion and interfacial adhesion were studied with scanning electron microscopy. From mechanical properties measurements, it was found that tensile and impact strength are both affected by the type and the amount of the used filler. The degree of crystallinity of PBSu was found to decrease by increasing the filler content, although that both fillers can act as nucleating agents. Finally, the degradation rate during enzymatic hydrolysis and soil burial increased in all biocomposites by increasing the filler content. PBSu/hemp shive composites showed higher biodegradation rates than PBSu/hemp fiber composites. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers
... Recently, extensive research has been done on the utilization of natural fibers including oil palm (Teh et al. 2013;Then et al. 2013Then et al. , 2014aThen et al. ,b, 2015aEng et al. 2014), kenaf (Mohd Sis et al. 2013), hemp (Terzopoulou et al. 2014), coir (Islam et al. 2010;Nam et al. 2011), rice straw (Zhao et al. 2012), and banana (Pothan et al. 2006) fibers as filler or reinforcements in fabricating of biocomposites, in place of synthetic fibers. These natural fibers show tremendous advantages relative to synthetic fibers, particularly due to their relatively lower density and production cost, in combination with their renewable, sustainable, and biodegradable characteristics (Terzopoulou et al. 2014). ...
... Recently, extensive research has been done on the utilization of natural fibers including oil palm (Teh et al. 2013;Then et al. 2013Then et al. , 2014aThen et al. ,b, 2015aEng et al. 2014), kenaf (Mohd Sis et al. 2013), hemp (Terzopoulou et al. 2014), coir (Islam et al. 2010;Nam et al. 2011), rice straw (Zhao et al. 2012), and banana (Pothan et al. 2006) fibers as filler or reinforcements in fabricating of biocomposites, in place of synthetic fibers. These natural fibers show tremendous advantages relative to synthetic fibers, particularly due to their relatively lower density and production cost, in combination with their renewable, sustainable, and biodegradable characteristics (Terzopoulou et al. 2014). These natural fibers are made up of three main components, namely cellulose, hemicellulose, and lignin, which are responsible for their physical and mechanical properties and are varied depending on the origin of the fibers (Georgopoulos et al. 2005). ...
... Nowadays, many interior and exterior parts of car compartments are made from natural fiber biocomposite materials due to the interesting properties of natural fibers such as light weight, low production cost and energy, ecological sustainable, and biodegradable as well as carbon dioxide neutral (Terzopoulou et al. 2014). Therefore, there is no doubt that the biocomposites made of PBS and OPMF may have showed potential application in automotive market. ...
Consecutive superheated steam-alkali treatment was introduced to modify oil palm mesocarp fiber (OPMF) prior to biocomposite fabrication. The biocomposite made up of 70 wt.% modified OPMF (SNOPMF) and 30 wt.% poly(butylene succinate) (PBS) was prepared by melt blending followed by compression molding. A silane coupling agent of 3-aminopropyltrimethoxysilane (APTMS) was also incorporated into the SNOPMF/PBS biocomposite during the compounding process to impart better adhesion at the SNOPMF-PBS interface. The experimental results revealed that the tensile, flexural, and impact strengths were enhanced by 16, 30, and 15%, respectively, after the introduction of 2 wt.% APTMS to the SNOPMF/PBS biocomposite. Similarly, the resistance to water uptake and thickness swelling of this biocomposite was improved by 34 and 49%, respectively, relative to SNOPMF/PBS biocomposite. The SEM observation of the tensile fracture surface showed that APTMS improved the interfacial adhesion between SNOPMF and PBS. Based on the results, it can be deduced that APTMS could be a good coupling agent for improving the SNOPMF-PBS adhesion and, thereby, lead to a water resistant biocomposite of enhanced mechanical properties.
... Natural fibers possess several advantages over synthetic fibers, such as low cost and low density, biodegradability, eco-friendliness, renewability, and high specific strength and stiffness relative to synthetic fibers (Terzopoulou et al. 2014). Furthermore, natural fiber can be obtained at a relatively low energy input with a lesser amount of CO2 emissions; they cause little abrasion to machinery during processing compared to synthetic fibers (Azizi Samir et al. 2005). ...
... According to recent publications, a wide range of natural fibers are being utilized as filler or reinforcement in various types of thermoplastic matrices to fabricate biocomposites; these include oil palm (Shinoj et al. 2010(Shinoj et al. , 2011aTeh et al. 2013;Eng et al. 2014;Rayung et al. 2014;Then et al. 2013Then et al. , 2014aThen et al. , 2015a, kenaf (Abdul , hemp (Terzopoulou et al. 2014), jute (Nam et al. 2012), coir (Nam et al. 2011), cotton stalk (Tan et al. 2011), sisal (Joseph et al. 2003), and banana (Pothan et al. 2003). ...
... As the temperature increased, the re-crystallized or more structurally perfect crystal melted and gave rise to the second melting endothermic peak (Zhang et al. 2012). A similar observation was reported by Terzopoulou et al. (2014) for hemp/PBS biocomposites. During the cooling scan, the DSC thermogram (Fig. 7) of neat PBS showed the presence of an exothermic peak. ...
Biodegradable and environmentally friendly biocomposites produced by a combination of biodegradable thermoplastics and natural fiber have gained increasing interest in recent years. In this work, eco-friendly biocomposites made from poly(butylene succinate) (PBS) and different weight percentages (10, 30, 50, and 70 wt%) of oil palm mesocarp fiber (OPMF) were fabricated via a melt blending process followed by hot-press molding. The biocomposites showed an improvement in storage and loss moduli with increasing fiber content, as indicated by dynamic mechanical analysis. Also, the water uptake and thickness swelling of the biocomposites increased with fiber content. The presence of fiber improved the biodegradability of the PBS, as evidenced from soil decomposition and scanning electron microscopy studies. Conversely, the presence of fiber lowered the melting and crystallization temperature as well as the thermal stability of neat PBS. The biocomposites from PBS and OPMF could be promising biocomposite materials because of their improved mechanical properties and biodegradability compared to neat PBS.
... Numerous complex compositions of multiple biodegradable polymers in various ratios are also used for that purpose [9][10][11][12]. Examples of such polymeric materials used to produce biocomposites include polylactide [13], polyvinyl alcohol [14], poly(hydroxyalkanoates) [15], polycaprolactone [16], and one of the more interesting-poly(butylene succinate) (PBS) [17]. PBS has very good functional properties that allow it to be widely used even in specific applications [18,19]. ...
... 150 °C. Therefore, PBS is suitable for the production of biocomposites with natural fillers because it has a low melting point (about 115 °C) [17,[58][59][60][61]. Thirdly, the mechanical strength of LCF biocomposites is usually inversely proportional to the filler content [4,21,50,62]. ...
... The fracture is brittle in nature and the energy is mainly utilized for crack propagation; so, the crack resistance decreases drastically with filler content [100,101]. Deterioration of the impact strength with the increasing natural filler content is a typical phenomenon for PBS-based biocomposites [17,21,36,67,102]. ...
The paper presents a procedure of the manufacturing and complex analysis of the properties of injection mouldings made of polymeric composites based on the poly(butylene succinate) (PBS) matrix with the addition of a natural filler in the form of wheat bran (WB). The scope of the research included measurements of processing shrinkage and density, analysis of the chemical structure, measurements of the thermal and thermo-mechanical properties (Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TG), Heat Deflection Temperature (HDT), and Vicat Softening Temperature (VST)), and measurements of the mechanical properties (hardness, impact strength, and static tensile test). The measurements were performed using design of experiment (DOE) methods, which made it possible to determine the investigated relationships in the form of polynomials and response surfaces. The mass content of the filler and the extruder screw speed during the production of the biocomposite granulate, which was used for the injection moulding of the test samples, constituted the variable factors adopted in the DOE. The study showed significant differences in the processing, thermal, and mechanical properties studied for individual systems of the DOE.
... Therefore, it is suitable for filling with LCF up to 50 wt.% [45][46][47][48]. ...
... This suggests it originates from the melting process rather than water evaporation. The presence of an additional peak on the DCS curves that originates from the melting process was also reported for PBS composites with palm fibers [87], PBS with rice straw [74], PBS with hemp fibers and with hemp shives [46], as well as PBS blends with polylactide and poly(3-hydroxybutyrate-co-hydroxyvalerate) [88] and even for neat PBS [89]. As was stipulated in these reports, this first endothermic peak can result from the melting of less-perfect crystals of PBS. ...
Unmodified poly (butylene succinate) (PBS) is characterized by very good processability; however, after the incorporation of various fillers of plant origin, its processing becomes much more complicated and its properties are significantly affected. Detailed studies of the processing aspects of PBS/wheat bran (WB) biocomposition are lacking, despite the addition of WB having a significant impact on both the production efficiency and the properties of end products. This research paper presents test results of the co-rotating twin-screw extrusion processing of a biodegradable polymer blend, the matrix of which was PBS, with WB as the filler. In undertaking this task, we examined the impact of extruder screw rotational speed and WB content on the characteristics of extrusion processing, as well as on certain thermal, physical, structural and processing properties of the obtained blend. The WB introduced to the blend was in the form of a selected fraction with particles smaller than 0.2 mm. The measurements were conducted using the Design of Experiment (DOE) methods, which enabled establishing the studied relationships in the form of polynomials and response surfaces. The determined extrusion process characteristics covered the impact of screw rotational speed and WB content on the mass flow rate of the processed blend and its pressure, the screw drive torque and specific energy consumption. The studies of the obtained polymer blend included determining the impact of the aforementioned variable factors on the melt flow rate (MFR) index, chemical structure (FTIR), thermal properties (differential scanning calorimetry (DSC), thermogravimetry (TG), derivative thermogravimetry (DTG)), p-v-T relationships, microstructure, density and moisture absorbance. Analysis of variance (ANOVA) was used to assess the effect of individual variable factors. The results of this work are presented, inter alia, using Pareto charts of standardized effects, which illustrate the influence of individual terms of the determined regression equations on the studied quantity.
... rough the scene change rate of the image, an adaptive image feature matching search window can be obtained, so that a more accurate matching search can be performed during the matching initialization and projection point matching process [18]. ...
With the continuous speed increase of high-speed trains, higher performance requirements are put forward for the braking technology and braking device. In order to improve productivity and overall competitiveness, manufacturing companies are actively researching new manufacturing technologies and production methods, and shop floor scheduling is one of the core components of this problem. This paper mainly studies the high-speed train composite workshop planning and scheduling optimization method. This experiment adopts B/S-based architecture mode. The prototype system is developed with Microsoft’s integrated development platform Visual Studio 2013, and Microsoft’s SQL Server 2008 is used as the background database management system. The experiment mainly uses the white box test method; the test content mainly includes module interface test, module local data structure test, and module boundary test. The interface parameters of each module are checked, and the boundary values of some functions are also analyzed and tested. According to the results, the planning management personnel revise the priority order again until all the molds meet the requirements of delivery and constraints. If the scheduled results do not meet the requirements, the methods such as those compressing the lead time, those urging the casting to be in place in advance, single process outsourcing, and overtime shall be considered. In this paper, a layered coding strategy is adopted. The first layer of coding represents the batch processing sequence. The second layer of coding determines to which process the corresponding batch belongs to. Each layer of coding is divided into different machine segments to represent the batch processing sequence on different machines. When the production process needs to switch orders, it can know which equipment parameters need to be adjusted in advance, which can effectively avoid the wrong operation caused by temporary adjustment of production parameters, reduce the order switching time, and improve the utilization rate of the production line. The data show that, compared with the artificial experience method and the priority rule method, the order production cycle after genetic optimization is reduced by 7.34% and 8.98%, respectively. The results show that the workshop scheduling optimization can help enterprises save stamping scheduling time, reduce production costs, and improve the rationality of scheduling.
... Natural fibers, such as cotton, hemp, and flax, are widely used for industrial applications, such as textiles additives [1,2], in order to increase the biodegradability of polymers [3], absorbent materials [4], etc. The excess of those materials are then considered as wastes with a special need for treatment. ...
Over the last several years, the trend of researchers has been to use some very low-cost materials as adsorbents. For this purpose, some already commercially used bast fibers were selected as potential adsorbent materials to remove basic dye from synthetic effluents. The adsorption of basic yellow 37 dye was studied using three different bast fibers under the names of flax, ramie, and kenaf. Their morphological structure was examined using several techniques such as scanning electron microscopy (SEM), crystallinity, X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), as well as those characterizations being a useful tool to propose a mechanism of the whole adsorption process. The adsorption evaluation was achieved by studying at first the pH (12) and temperature effects (25–55 °C). Two isotherm models (Langmuir and Freundlich) were also applied to the experimental equilibrium data revealing the superiority of ramie fibers (327, 435, and 460 mg·g−1 (25 °C) for kenaf, flax, and ramie, respectively). The crucial adsorbent’s dosage was found to be 0.1 g per litre for all fibers, while the completed desorption study (eluant’s pH and reuse cycles) also confirmed the strong potential of these kinds of fibers as adsorbents. The latter may be attributed to the cellulosic content.
... Moreover, because of their high strength and stiffness, several authors recently reported hemp fiber as reinforcement in composites. [21][22][23][24] Jute Jute (Corchorus capsularis/Corchorus olitorius) is the most well-known and important natural fiber after cotton. [25] Native to the Mediterranean, Jute is cultivated in India, Bangladesh, China, Nepal, Thailand, Indonesia, and Brazil. ...
There is increasing interest on the development of highly performing value-added products from
natural and renewable resources due to the challenges of petroleum-based products. The increased
desire for green products in addition to the low cost, recyclability, and weight reduction are the
key interest for natural fber reinforced composites. The recent development on the value-added
applications of natural fber reinforced polymeric composites with respect to their comparability to
synthetic counterparts were reviewed. It also gives an overview of various naturally occurring fbers
with their type, source and surface modifcations and their composites from both synthetic and bio
based. The recent reports on natural fber reinforced composites based value-added products in the
feld of construction, automotive, and packaging are discussed with their advantages and disadvantages. It also emphasizes future research perspectives and concludes with key issues that need to be
resolved.
... To the best of our knowledge, many studies in literature investigated the degradation of PBS in terrestrial environments [8,[21][22][23][24]; however, only few works focused on the PBS degradation in aqueous environments. Kint et al. [19] and Kanemura et al. [4] reported that PBS and PBS copolymers can exhibit pronounced hydrolytic degradability, which increases with the content of 1,4-butylene succinic units. ...
The present work investigated the degradation of poly(butylene succinate) (PBS) in different aqueous media, as PBS microparticles are intended for use in personal care and cosmetic applications. Degradation tests were performed for the first time at different conditions of salinity, pH and temperature for two types of PBS: microparticles produced through suspension polycondensations and commercial pellets produced through bulk polycondensations. As shown experimentally, rates of PBS degradation were sensitive to modification of degradation conditions, being faster at higher temperatures, at acidic conditions and at alkaline conditions. However, PBS degradation was not very sensitive to the presence of salts, although degradation rates were shown to be higher in real sea water samples. Additionally, rates of PBS degradation were shown to depend significantly on PBS properties and morphology. Based on the obtained experimental data, a model was proposed to evaluate the effects of degradation temperature and particle morphology on the rates of PBS degradation in sea water, providing suitable fits for the available data. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
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... Poly(butylene succinate) has been successfully used as matrix with a wide variety of natural fibers such as sisal [28], hemp [29], kenaf [30], and so on. Regarding PBS composites with agricultural wastes, it is worthy to note the work by Tserki et al. [31], in which, lignocellulosic waste flours (spruce, olive husk and paper) were used as fillers into PBS matrices. ...
In this work poly(butylene succinate) (PBS) composites with varying loads of almond shell flour (ASF) in the 10–50 wt % were manufactured by extrusion and subsequent injection molding thus showing the feasibility of these combined manufacturing processes for composites up to 50 wt % ASF. A vegetable oil-derived compatibilizer, maleinized linseed oil (MLO), was used in PBS/ASF composites with a constant ASF to MLO (wt/wt) ratio of 10.0:1.5. Mechanical properties of PBS/ASF/MLO composites were obtained by standard tensile, hardness, and impact tests. The morphology of these composites was studied by field emission scanning electron microscopy—FESEM) and the main thermal properties were obtained by differential scanning calorimetry (DSC), dynamical mechanical-thermal analysis (DMTA), thermomechanical analysis (TMA), and thermogravimetry (TGA). As the ASF loading increased, a decrease in maximum tensile strength could be detected due to the presence of ASF filler and a plasticization effect provided by MLO which also provided a compatibilization effect due to the interaction of succinic anhydride polar groups contained in MLO with hydroxyl groups in both PBS (hydroxyl terminal groups) and ASF (hydroxyl groups in cellulose). FESEM study reveals a positive contribution of MLO to embed ASF particles into the PBS matrix, thus leading to balanced mechanical properties. Varying ASF loading on PBS composites represents an environmentally-friendly solution to broaden PBS uses at the industrial level while the use of MLO contributes to overcome or minimize the lack of interaction between the hydrophobic PBS matrix and the highly hydrophilic ASF filler.
... The hemp by-products are both used as animal bedding as main application thanks to their high absorption capacity (Karus and Vogt, 2004). Hemp hurds could also be integrated as filler in plastic composites (Terzopoulou et al., 2016;Li et al., 2017), used in buildings (Shea et al., 2012) or in antibacterial applications (Khan et al., 2015). It can also be considered as raw material for a fractionation process into Organosolv lignin (Gandolfi et al., 2014), sugar streams to produce L-lactic acid (Gandolfi et al., 2015) or for a Formosolv process to produce pulp (De Vega and Ligero, 2017). ...
This work aims at developing a continuous intensified green process to extract high-value added molecules from industrial hemp by-products. Hemp hurds and hemp dust were studied as potential sources for the production of two hydroxycinnamic acids (HCA): ferulic (FA) and p-coumaric acids (p-CA). Prior to pilot scale extraction, FA and p-CA analytical contents were evaluated to 0.3 and 3.5 g/kg dry matter (DM) for hemp hurds and 0.1 and 0.8 g/kg DM for hemp dust as potentials of reference. The continuous pilot scale extraction was then carried out using twin-screw extrusion. Mild conditions were developed: 50 °C, alkaline aqueous or hydroalcoholic solvent (less than 0.5 M NaOH) and low liquid to solid ratios. The mechanical effect helps the diffusion of the solvent, promotes the hydrolysis of the ester and ether bonds and favors the extraction of HCA in a short time. Yields in p-CA and FA reached 50% and 33% of the free and bound contents for hemp hurds. For hemp dust, all of p-CA was extracted whereas 60% of FA was recovered. The solid residue may be submitted to a second extraction stage with a polar solvent in order to increase HCA recovery. Extraction by extrusion could be seen as an alternative green processing technique as it is responsible for a reduction of extraction time and energy and a decrease in solvent and reagent consumptions.
... After 3 days of soaking, a few holes appear on the surface of neat PCL, and as the degradation proceeds in 9 days, it becomes rougher. At 15 days morphologies that witness the presence of crystals appear, suggesting that hydrolysis occurs first in the amorphous parts and after that crystalline regions are exposed on the surface [5,72,73]. A similar trend is observed for all nanocomposites as well. ...
Poly(ε-caprolactone) (PCL) is a bioresorbable synthetic polyester widely studied as a biomaterial for tissue engineering and controlled release applications, but its low bioactivity and weak mechanical performance limits its applications. In this work, nanosized bioglasses with two different compositions (SiO2-CaO and SiO2-CaO-P2O5) were synthesized with a hydrothermal method, and each one was used as filler in the preparation of PCL nanocomposites via the in situ ring opening polymerization of ε-caprolactone. The effect of the addition of 0.5, 1 and 2.5 wt % of the nanofillers on the molecular weight, structural, mechanical and thermal properties of the polymer nanocomposites, as well as on their enzymatic hydrolysis rate, bioactivity and biocompatibility was systematically investigated. All nanocomposites exhibited higher molecular weight values in comparison with neat PCL, and mechanical properties were enhanced for the 0.5 and 1 wt % filler content, which was attributed to extensive interactions between the filler and the matrix, proving the superiority of in situ polymerization over solution mixing and melt compounding. Both bioglasses accelerated the enzymatic degradation of PCL and induced bioactivity, since apatite was formed on the surface of the nanocomposites after soaking in simulated body fluid. Finally, all samples were biocompatible as Wharton jelly-derived mesenchymal stem cells (WJ-MSCs) attached and proliferated on their surfaces.
... WPC products have many applications in the construction, interior decorating, household appliance, and transportation industries [4]. With growing awareness of the global environmental energy crisis and resource constraints, extensive research has been conducted into the use of bio-based and biodegradable plastics, such as poly(lactic acid) (PLA) [5,6], poly(butylene succinate) [7], and poly(butylene adipate-co-terephthalate) [8], in WPC to replace non-degradable plastics, such as polyethylene, polypropylene, polyvinyl chloride, and polystyrene, which are derived from petroleum resources. The use of biodegradable polymers to produce environmentally-friendly bio-composites is a promising trend [9,10]. ...
This study aimed to evaluate the effect of styrene-assisted maleic anhydride-grafted poly(lactic acid) (PLA-g-St/MAH) on the interfacial properties of wood flour/poly(lactic acid) (PLA) bio-composites. PLA-g-St/MAH was synthesized by free-radical melt grafting using styrene as a comonomer and dicumyl peroxide as an initiator. The structure of PLA-g-St/MAH was characterized by Fourier transform infrared spectroscopy. Wood flour/PLA composites were prepared by compression molding using PLA-g-St/MAH as a compatibilizer. The effects of PLA-g-St/MAH on the rheological and mechanical properties, as well as on the fractured surface morphology of the composites were investigated. Results indicated that storage modulus, complex viscosity, equilibrium torque, and shear heat were significantly increased. The mechanical properties of the wood flour/PLA composites were also significantly increased after the addition of PLA-g-St/MAH. The maximum values were achieved at the loading rate of 3 wt % because of the improved interfacial adhesion between the wood flour and the PLA matrix.
... Weight loss and crystallinity changes measured by DSC allowed to follow the degradation rate due to the action of microorganisms during soil burial test. The presence of fillers increased the rate of degradation in all the biocomposites examined, in particular in the PBSu/hemp shive composites [110]. Even the effects of crosslinking on mechanical properties and biodegradability of "protein-based" green composites were studied. ...
Green composites have gained attention as promising alternatives to the traditional ones, mainly for their potential biodegradability. They are a combination of biodegradable polymers with natural fibres. Frequently, a compatibilization of polymeric matrix and fibre/filler for improved green composites is necessary. However, the treatments can prejudice the biodegradability of the final material. As a consequence, biodegradation tests have to been carried out. For this reason, this chapter provides an overview of both the standardization methods used to determine a degree of biodegradation in different environments and the laboratory procedures commonly adopted. Moreover, it summarizes studies in the literature, published between the beginning of 2009 and May 2019, concerning the assessment of biodegradability of green composites.
... The inorganic waste material is generally not biodegradable and cause toxicity to the living being. 1 On the other hand, natural fibers and bio-based polymers and fillers are fully biodegradable materials. [2][3][4] Due to their light weight and low cost, the natural fiber reinforced composite materials are being preferred in automobiles and construction applications. [5][6][7] These composites; however, have some weaknesses among which high flammability is of critical importance. ...
Natural fibers and bio-based composites are competitive to conventional materials in structural and transportation industry. Natural fibers reinforced polymer matrix composites are familiar/common materials currently. Various properties of these composites have been explored in the already available literature, and has been continuing with new developments. They have a risk of flammability in most of the applications which is undesirable. Fire retardant natural fiber and bio-based composite materials have recently gained researchers' interest. This paper summarizes recent progress regarding flammability of natural fiber and bio-based composites. The mechanism of fire retardancy has been explained. The factors affecting flammability of such composites and characterization techniques required for evaluating fire retardancy have also been described in detail. The reported effects of fire retardant include practices on the other properties of composites.
... Nowadays, the use of biodegradable materials in various areas same as agriculture [30], tissue engineering [31], food coating [32], packing technology [33], and drug delivery systems [34], has gained an increased attention. Employing synthetic or natural biodegradable structures in drug delivery systems, provides to implant them in human body without any concern about further treatment for removing them [35,36]. ...
In this study, a new biodegradable cross-linker agent based on fructose was reported for fabrication of brain targeted molecularly imprinted polymer (MIP). The applied strategy for targeting drug delivery was based on two mechanisms. Firstly, the magnetic structure of prepared MIP which facilitates the aggregation of carrier near target tissue under magnetic field. Second, the tendency of brain cell to use the produced fructose during degradation of MIP as fuel. In synthesis procedure magnetic fluorescent multi core shell structure MIP was prepared via co-precipitation polymerization in the presence of olanzapine as template and fructose with double acts, as monomer and cross-linker. Various kinds of in vitro and in vivo experiments were carried out to indicate the considered properties of carrier. The obtained data confirmed the designed carrier olanzapine satisfactorily meet the requirement in brain drug delivery application.
... In particular, the results of tensile and flexural properties are summarized in Table 4). This is not in agreement with the results obtained by Terzopoulou et al. (2014), that reported low mechanical properties after melt mixing of PBS and hemp fibers. In our work, all the composites are characterized by the phenomenon of "fiber bridging" after flexural tests and furthermore they do not ultimately break (Fig. 11). ...
The retting process, carried out with warm inoculated water, has been evaluated as a potential method to modify the structure of fibers in order to prepare polymeric biocomposites. The efficiency of the method was tested by analyzing the final performances of the produced composites, prepared with reinforcing hemp fibers (Cannabis sativa L.) dispersed in poly(butylene succinate) (PBS) biopolymer matrix. It turns out that the retting process influences the chemical composition of fibers, removing lignin, pectin, waxes and minor components and, then, disaggregating the pectin-lignin matrix that bounds the elementary hemp fibers and creates fiber bundles. The process improves wettability of fibers as well as their compatibility with the polar functional groups of the polymeric matrix. The retting treatment, commonly applied to get higher fiber quality, helps improve the adhesion to the polymer matrix, thus creating a stronger interface and therefore superior composite performances. As a result, the composites, that always benefit from the presence of fibers in terms of mechanical properties, provide the best performances in the presence of retted hemp fibers, in particular with the composition of 20. wt%.
... For this reason, some research works have focused on manufacturing composite materials with natural fibers [10][11][12]. Thus, PBS has been used as a matrix for composites with hemp fiber [13], which contributes to lowering the overall cost of the developed material, making this a more environmentally friendly material. The use of wool waste in PBS composites has also been reported [14]. ...
Green composites of poly(butylene succinate) (PBS) were manufactured with almond shell flour (ASF) by reactive compatibilization with maleinized linseed oil *MLO) by extrusion and subsequent injection molding. ASF was kept constant at 30 wt %, while the effect of different MLO loading on mechanical, thermal, thermomechanical, and morphology properties was studied. Uncompatibilized PBS/ASF composites show a remarkable decrease in mechanical properties due to the nonexistent polymer‒filler interaction, as evidenced by field emission scanning electron microscopy (FESEM). MLO provides a plasticization effect on PBS/ASF composites but, in addition, acts as a compatibilizer agent since the maleic anhydride groups contained in MLO are likely to react with hydroxyl groups in both PBS end chains and ASF particles. This compatibilizing effect is observed by FESEM with a reduction of the gap between the filler particles and the surrounding PBS matrix. In addition, the Tg of PBS increases from −28 °C to −12 °C with an MLO content of 10 wt %, thus indicating compatibilization. MLO has been validated as an environmentally friendly additive to PBS/ASF composites to give materials with high environmental efficiency.
... Poly(butylene succinate) (PBS) is a thermoplastic aliphatic semicrystalline polyester that has properties comparable to PP and is also biodegradable. Hemp fillers in amounts of up to 70% in composites, accelerate the biodegradation of PBS in enzymatic hydrolysis, and especially in soil burial, shives having higher effects than fibers [87]. ...
Polymer composites are widely used modern-day materials, specially designed to combine good mechanical properties and low density, resulting in a high tensile strength-to-weight ratio. However, materials for outdoor use suffer from the negative effects of environmental factors, loosing properties in various degrees. In particular, natural fillers (particulates or fibers) or components induce biodegradability in the otherwise bio inert matrix of usual commodity plastics. Here we present some aspects found in recent literature related to the effect of aggressive factors such as temperature, mechanical forces, solar radiation, humidity, and biological attack on the properties of plastic composites containing natural fillers.
... In composites, more often than not, bast fibers are chosen as reinforcing materials [5, 6]. Hemp, kenaf, ramie and yute are among the most extensively studied natural fibers for polymer reinforcement and green composites78910111213. Furthermore, their low density, coupled with good mechanical performance and good thermal resistance , make them attractive candidates for polymer hybrids . ...
In the present work, the effective use of poly-ethylene-grafted maleic anhydride (PEg -MA) copolymer as a compatibilizer in high-density polyethylene composites containing 10–50 mass% hemp fibers was evaluated through mechanical and thermal properties measurements. The results revealed a significant reinforcement on the tensile strength of the composites as a consequence of the incorporation of the compatibilizer. Less pronounced effects were found on the elongation at break and impact strength of the composites. The notable enhancement of tensile strength on the compatibilized composites was related to the improved adhesion of hemp with the matrix in the presence of PEg -MA, which was revealed through scanning electron microscopy observations. Furthermore, Fourier transform infrared spectroscopy analyses suggested that covalent bonding occurs between the fibers and the matrix in the highest PEg -MA concentrations. Differential scanning calorimetry experiments revealed that the presence of compatibilizer increases the crystallinity of the composites. Thermogravimetry studies revealed that for low compatibilizer concentrations the thermal stability of the composites is further reduced, while for the highest concentration, when bonding occurs, it is enhanced. The biodegradation studies of all the composites revealed that the incorporation of compatibilizer enhances the stability of the composites, especially in the higher concentrations, and reduces their final residue.
... Mainly when WPCs meet humidity, temperature, and other environmental factors, unwelcome changes in color and peeling of layers can be observed. Many methods, like surface grafting, chemical treatment, and cellulose coating, have been applied successfully to overcome these challenges [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. ...
The transition from fossil-based to bio-based materials requires in-depth environmental durability analysis for material engineering and construction applications. We report the hydrothermal aging and biodegradation effect on 6 types of compatibilized microcrystalline cellulose (MCC) and poly(butylene succinate) (PBS) composites. The prepared highly loaded systems with 70 wt% of MCC showed a strong positive impact on the composites’ mechanical and thermomechanical properties concerning applied modifications. MCC was modified with different coupling agents, namely polyhydroxy amides (PHA), alkyl ester (EST), (3-Aminopropyl)trimethoxysilane (APTMS), maleic acid anhydride, and polymeric diphenylmethane diisocyanate (PMDI). In addition, cross-linking agent carbodiimide (CDI) was used as an alternative to MCC modification. Modification of MCC compared to unmodified composite induced the enhanced rigidity, creep properties, and thermal stability of the materials due to the cross-linking in the interface by proposed chemical treatment. PMDI and CDI chemical modification resulted in the highest elastic modulus while keeping high strength values. A significant 2.5-fold reduction of the coefficient of linear thermal expansion and decreased thermal strains for modified biocomposites were obtained. Due to the hydrophilic nature of MCC, the hydrothermal aging of the composites revealed a dramatic decrease in the elastic modulus and strength characteristics compared to neat PBS. The hydrophilicity depends on the applied surface modification as indicated by contact angle measurements and water absorption and swelling tests. EST facilitated water wetting and enhanced water penetration, and reduced material biodegradation to 30 days, a 2.5-fold improvement compared to the neat PBS polymer. In contrast, PHA, APTMS, PMDI, and CDI improved biocomposites durability while suppressing biodegradation. The obtained results could be useful for selecting an optimal MCC surface modification route to design novel and perspective biocomposites with tailored durability and biodegradation and to replace polyolefin composites for wood polymer composite applications.
... In the literature, different attempts have been made in this sector, adding to PBS several types of natural fibers [124,125] and natural wastes such as rice straw [126], jute fibers [92], pineapple fibers [127], bamboo fibers [128] or hemp fibers [129]. However, compatibility with the matrix is fundamental to achieve a significant enhancement of PBS composites; for example, in the work of Liminana et al., interesting results were achieved for PBS composites containing 30 wt.% of almond shellflour (ASF) by using appropriate compatibilizers [128]. ...
PBS, an acronym for poly (butylene succinate), is an aliphatic polyester that is attracting increasing attention due to the possibility of bio-based production, as well as its balanced properties, enhanced processability, and excellent biodegradability. This brief review has the aim to provide the status concerning the synthesis, production, thermal, morphological and mechanical properties underlying biodegradation ability, and major applications of PBS and its principal copolymers.
... The hydrogen bonds between different chemical components provide stiffness and mechanical strength of hemp shives. For example, hemicellulose determines the thermal degradation and moisture absorption, while the lignin content determines the UV degradation of the hemp shives [30,31]. Hemp shives offer several advantages, such as sufficient reactive functional groups, high carbon content, compatibility with diverse industrial chemicals, good stability and mechanical properties due to the presence of aromatic rings, and good rheological and viscoelastic properties, making it a potential candidate to be used as reinforcing material in polymer composites. ...
Polyurethane (PUR) foams reinforced with 2 wt.% hemp shives (HS) fillers were successfully synthesized. Three different types of HS fillers were evaluated-non-treated HS, HS impregnated with sunflower oil (SO) and HS impregnated with tung oil (TO). The impact of each type of HS fillers on cellular morphology, mechanical performances, thermal stability, and flame retardancy was evaluated. It has been shown that the addition of HS fillers improved the mechanical characteristics of PUR foams. Among all modified series, the greatest improvement was observed after the incorporation of non-treated HS filler-when compared with neat foams, the value of compressive strength increased by ~13%. Moreover, the incorporation of impregnated HS fillers resulted in the improvement of thermal stability and flame retardancy of PUR foams. For example, the addition of both types of impregnated HS fillers significantly decreased the value of heat peak release (pHRR), total smoke release (TSR), and limiting oxygen index (LOI). Moreover, the PUR foams containing impregnated fillers were characterized by improved hydrophobicity and limited water uptake. The obtained results confirmed that the modification of PUR foams with non-treated and impregnated HS fillers may be a successful approach in producing polymeric composites with improved properties.
... This can be attributed to many factors, such as incompatibility between the matrix and the fibers, improper production processes, and fiber degradation. It should be noted that the composite properties are also affected by structural factors such as incorrect fiber orientation, inadequate fiber content in the polymer matrix and uneven fiber distribution (lack of proper homogenization of the fiber-matrix blend) [14][15][16]. ...
The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was used to prepare biocompatible composites modified by the hemp fibers. The aim of the study was to assess the structure and selected thermal and mechanical properties of the obtained biocomposites. The morphology of samples was analyzed using a scanning electron microscope and a computed tomography analysis. The phase transitions of composites and polymer matrix were investigated using differential scanning calorimetry. Moreover, the non-equilibrium and equilibrium thermal parameters of composites and the unfilled PHBV were established based on the thermal history. Knowing equilibrium parameters, i.e., the heat of fusion for the fully crystalline materials, ΔHf (100%), and the change of heat capacity at glass transition temperature (Tg) for the fully amorphous, ΔCp (100%), composites, the degree of crystallinity, mobile, and rigid amorphous fractions were estimated. The addition of hemp fibers to the PHBV matrix caused around a two-time increase in the degree of crystallinity in reference to the unfilled PHBV. It was also observed that the addition of hemp fibers caused a decrease in heat capacity for fully amorphous material for all the biocomposites obtained. A similar relationship was observed in case of values of the heat of fusion for fully crystalline material. Simultaneously, the decrease in amorphous phase contents was noted. It was also noted that the rigid amorphous fraction exists only for the unfilled polymer matrix. Some mechanical properties of investigated materials were also measured and presented.
... 49 To date, the slow degradation of PLA due to its hydrophobicity could be improved by the introduction of hydrophilic fillers into PLA matrix. 11,50 In this present work, RH, the hydrophilic agricultural waste, was introduced into PLA and the biodegradability of PLA/PBS/RH green composites was studied by measuring their visual change, chemical structure alteration, reduced weight and deteriorated tensile properties in a gardening soil burial test, lasting for 180 days. The results are presented in Figure 6-7. ...
This work aims to study the possibility to process PLA/PBS/RH green composites into hexagonal plant‐pots employing a large‐scale industrial operation using injection molding. Green composites based on poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and rice husk (RH) with various RH contents (10–30%wt.) were produced successfully using a twin‐screw extruder. The compatibility of RH‐matrix was improved by chemical surface modifications using a coupling agent. RH was analyzed as an effective filler for PLA to develop green composites with low cost, high biodegradability, improved processability, and comparable mechanical properties as unfilled PLA. With increasing RH content, tensile modulus of the composites increased gradually. The addition of PBS, at PLA/PBS ratio of 60/40, improved the elongation at break and impact strength of PLARH30 by 55% and 7.1%, respectively. The suitable processing temperatures for PLA decreased from 220–230°C to 170–180°C when 30%wt. RH was composited into PLA matrix and were further reduced when PBS was applied. After biodegradation via either enzymatic degradation or hydrolysis, surface erosion with a large number of voids, mass loss, and the substantial decrease in tensile strength of all the composites were observed. In addition, the biodegradation of the composites has been improved by the addition of either RH or PBS. This image designed by Supranee Kaewpirom and Anan Sirichalarmkul shows the possibility to process PLA/PBS/RH green composites into hexagonal plant‐pots employing a large‐scale industrial operation using injection molding. Manufacturability was optimized with Moldex 3D computer aid engineering (CAE). The CAE results were subsequently used as a reference guide in the mold trial injection process. The data from mold trial process revealed that as the RH content increased the suitable processing temperatures reduced accordingly.
... PBS is perfect for filling with natural fillers. This is due to its low melting point of 115 • C, which enables a lower processing temperature range and prevents thermal degradation of a filler, as well as due to the hydrophilic nature of macromolecules, which ensures a high degree of material filling, even without the use of a compatibilizer [33][34][35]. The presence of a filler deteriorates the processability of the material by increasing the viscosity of the composition, which, in turn, affects the efficiency of the injection molding process and the drive system load, as well as modifies the crystallization temperature and the degree of crystallinity, thus affecting the cooling behavior of the composition and the characteristics of mold shrinkage [36,37]. ...
This paper presents the assumptions of a thermodynamic equation of state for polymers according to the Renner model. The experiments involved extruding a biocomposite based on poly(butylene succinate) that was filled with ground wheat bran with its size not exceeding 200 μm. The biocomposite was produced in pellet form with three different contents by weight of wheat bran, i.e., 10%, 30% and 50%. All specimens were examined for their thermodynamic p-v-T characteristics. Taking advantage of the SimFit module of Cadmould 3D-F, experimental results were used to determine the coefficients of thermodynamic equation of state for the tested biocomposite according to the Renner model. The coefficients were then used to calculate transition temperature and to create diagrams illustrating the relationship between pressure, temperature and specific volume for the tested biocomposite. The obtained results can serve as a basis for assessing the suitability of the biocomposite for injection molding, selecting technological parameters of this process, as well as for analyzing shrinkage and defects of injection-molded parts.
Point-of-use (POU) water treatment technology in developing countries and rural regions is more feasible than a centralized water treatment system due to the high cost of pipe distribution. The water filtration system can provide quick and easy access to water with low maintenance and higher pathogen removal among POU technologies. However, non-biodegradable polymeric materials for water filtration membranes raise environmental concerns due to their problematic disposal. There is increasing research on biodegradable membrane material, but the validation of biodegradability is still lacking as measuring weight loss does not guarantee the complete mineralization of biodegradable membrane. This review aims to discuss various abiotic and biotic factors affecting polymer degradability in soil or compost, gather and evaluate existing studies on biodegradable filtration membrane and identify existing methods used to validate membrane biodegradability. Different kinetic models used to understand the biodegradation mechanism at different stages were studied. Factors affecting morphology and surface properties affect biodegradability. Membrane biodegradation follows a first-order model followed by a lag phase. Finally, future studies of biodegradable filtration membrane could include CO2 quantification and phytotoxicity studies, exploring different additives and membrane formulations to balance membrane performance and degradation ability, and lastly, conducting LCA and TEA to assess overall sustainability.
Nanofibrillated cellulose (NFC) is a sustainable functional nanomaterial known for its high strength, stiffness, and biocompatibility. It has become a key building block for the next-generation of lightweight, advanced materials for applications such as consumer products, biomedical, energy storage, coatings, construction, and automotive. Tunable and predictable durability under envi-ronmental impact is required for high performance applications. Bio-based poly (butylene succinate) (PBS) composites containing up to 50% NFC content were designed and aged in distilled water or at high relative humidity (RH98%). PBS/NFC composites are characterized by up to 10-fold increased water absorption capacity and diffusivity and the data are correlated with model calculations. Aged samples exhibited decreased crystallinity and melting temperature. Incorporation of NFC into PBS showed up to a 2.6-fold enhancement of the elastic modulus, although accompanied by a loss of strength by 40% and 8-fold reduction in the strain at failure of maximally loaded composites. Hy-drothermal ageing had almost no influence on the tensile characteristics of PBS; however, there were considerable degradation effects in PBS/NFC composites. Altered reinforcement efficiency is manifested through a 3.7-fold decreased effective elastic moduli of NFC determined by applying the Halpin–Tsai model and a proportional reduction of the storage moduli of composites. The adhesion efficiency in composites was reduced by hydrothermal ageing, as measured Puckanszky’s adhesion parameter for the strength, which decreased from 3 to 0.8. For the loss factor, Kubat’s adhesion parameter was increased by an order. PBS filled with 20 wt.% NFC is identified as the most efficient composition, for which negative environmental degradation effects are counterbalanced with the positive reinforcement effect. The PBS matrix can be used to protect the NFC network from water.
Environmental awareness across the world has motivated researchers to focus their attention on the use of cellulosic fiber as reinforcement in polymer matrices. Lignocellulosic fibers are an abundantly available resource in all countries, which is cheap and easily renewable. Also, due to their properties, cellulosic plant fibers exhibit a great potential for use in polymer reinforcement. As a result, considerable research and development efforts have been directed towards the use of cellulosic fibers as a reinforcing material in composites. The use of cellulosic fiber reinforced composites has continuously increased during recent years, which benefits the cultivation of fiber plants and the economy of the country. This research area continues to be of interest to both industry and academia, the use of cellulosic fibers in composite applications being investigated throughout the world. Cellulosic fiber reinforced composites are reasonably strong, lightweight, harmless to human health and the environment, and biodegradable, hence they have the potential to be used in various applications. Recent progress in cellulosic fiber composites research has illustrated their great potential as structural components in automobiles, aerospace structures, construction, and building, and so forth. This study is an effort to create awareness about the research works that have been published in the field of natural fiber composites. This review briefly illustrates the main paths and results of major research published in the field of natural fiber reinforced polymer composites. The topics covered include the aspects of fiber treatment to improve the mechanical properties of the composites, manufacturing methods, performance of hybrid composites, effect of laminate configuration, and many different applications of natural fiber composites. By presenting a systematic view of the work performed in this area so far, this review will hopefully serve as a starting point for the development of new ideas in the research on natural fiber polymer composites.
Rising energy concerns, rapid infrastructure development, and greater environmental awareness have fueled the demand for sustainable materials. In this direction, sustainable bio-based polymer generated from different resources through several operations can meet most of the annual synthetic plastics demand at least in Europe. The advancement of sustainable technologies for the effective utilization of sustainable materials for bioplastic and biomaterials production can afford a novel biorenewable source of sustainable products and biofuel as well as address the rising environmental concerns. Poly(butylene succinate) is one biopolymer that has enormous potential to be used in a wide range of applications. There is currently no extensive review on the PBS based polymer covering the advanced technologies for the development of high-value material. This article covers the advanced state of synthesis, process integrating biological and thermochemical conversion to produce bioplastics (PBS), physico-chemical and mechanical properties, and the recent applications. We have also provided a structural perspective on how PBS can be adopted via appropriate engineering/ modification to its properties. Different changes in the precursors of polymer materials and composites enable a various range of applications, including but not limited to the manufacturing of high-performance polymer materials to composites.
Crystallization of polylactic acid (PLA) has a profound effect on its thermal stability and mechanical properties. However, almost no crystallization occurs in actual injection molding process due to rapid cooling program. In this paper, flax fiber was employed as nucleator to enhance the crystallization capability of PLA. Effects of flax fiber content on cold crystallization, melt crystallization, crystallinity, crystal form, morphologies, and size of spherulites of PLA/flax fiber composites were investigated. Dynamic mechanical analysis was innovatively employed to study cold crystallization temperature of PLA/flax fiber composites under dynamic force, and the relationship between cold crystallization temperature (y) and flax fiber content (x) data was fitted by the function y = 34.1 × exp (−x/5.7) + 78.0. The differential scanning calorimetry results showed that the cold crystallization temperature of composites dropped, the melt crystallization temperature of composites increased, and the crystallinity of composites improved with increasing of flax fiber content. Using polarized optical microscopy, it has been found that the spherocrystal size of composites was much smaller than that of neat PLA, and flax fiber induced transcrystallization on the flax fiber surfaces. Wide-angle X-ray diffraction was applied to reveal that flax fiber significantly enhanced the formation of α-form PLA crystals.
Kenaf cellulose fiber was extracted from kenaf locally grown in Thailand as a potential local renewable resource for the cellulose fiber. In this study, the biodegradable polymer composites, poly(butylene succinate) (PBS)/cellulose fiber composites with different types of cellulose were prepared. The kenaf fiber treated with hydrochloric acid (KTH), extracted cellulose fiber (EC), and commercial cellulose fiber (CC) were selected as alternative renewable fillers in the PBS (the biodegradable polymer). Regarding the fiber characteristics, the aspect ratio of the EC (11.5) was found to be higher than that of the CC (6.1). In a similar manner, the EC contained 65.9% crystallinity, which was higher than that of the CC (37.0%) and the KTH (58.9%). Moreover, the EC exhibited higher thermal stability (Td[Max] = 362.9°C) than the CC (Td[Max] = 302.0°C) and the KTH (Td[Max] = 353.8°C). For PBS/cellulose fiber composites, the rheological, tensile, and thermal properties were studied. The rheology results revealed that the addition of the fiber changed the PBS microstructure. The EC fiber dispersion in the PBS seemed to be better than the others; however, the KTH fiber dispersion was poor. The addition of the fiber raised the elastic moduli of the composites by 5‐26%; however, it reduced the tensile strengths (by 14‐53%) and the decomposition temperatures (by 1‐2%). Furthermore, the addition of the fiber slightly affected the crystallization temperatures and melting temperatures of the composites. The yellowness and whiteness of the composites were marginally reduced. The composite with the EC fiber showed a significant improvement in the elastic modulus as compared to the composite with the CC fiber, while the tensile strength and the strain at maximum stress were comparable. Thus, according to the rheological, thermal, and tensile properties of the composites, the EC fiber showed a possibility of using as an alternative reinforcement material from a local renewable resource.
In this work, two poly(ether-block-amide) thermoplastic elastomers (Pebax® 2533 and Pebax® 5533) were subjected to five extrusion cycles. We characterized the various performance changes of the two materials after injection molding, including chemical structure, crystalline properties, and mechanical properties, and also analyzed the reasons for the observed changes. ATR-FTIR spectrum shows that after repeated extrusion, free hydroxyl groups and new oxygen-containing functional groups (carbonyl groups) were formed inside the materials. XPS shows that the oxygen content of the material increased significantly. TGA shows that the thermal stability of the material was slightly improved. The elastomers’ melt index also increased with extrusion cycles. Through analyzing the crystalline properties (DSC, XRD) of the materials, we tentatively explain the different changes in the two Poly(ether-block-amide) thermoplastic elastomers in terms of mechanical properties.
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This study investigated the effects of poly(butylene-succinate) (PBS) and cassava pulp (CP) at two particle sizes (250 and 400 µm) on the properties of PBS/CP biocomposites. The PBS/CP biocomposites with different ratios (PBS100/CP0, PBS90/CP10, PBS80/CP20, PBS70/CP30, and PBS60/CP40) were prepared using a twin-screw extruder and formed using a ram extruder. The physical, mechanical, and biodegradable properties of these biocomposites were studied. The results showed that the melt flow index of biocomposites significantly decreased with an increase in the CP content as observed in both CP particle sizes. It was also observed that using 400 µm CP in PBS80/CP20 led to a higher melt flow index as compared to using 250 µm CP. The PBS/CP biocomposites were shown to improve Young's modulus and hardness. Nevertheless, tensile strength, elongation at break, and impact strength of the PBS/CP biocomposites decreased with an increase in the amount of CP (in both particle sizes). The addition of 250 µm CP provided good particle dispersion and compatibility in the biocomposite matrix. An increase in the CP content of up to 40% showed that the biocomposites had more brittle fracture although they were also the best biodegradable as indicated by natural soil burial test for 42 days. A biocomposite from PBS/CP could be useful in commodity packaging, outdoor plant pots, and injection molding as eco-friendly, strong and biodegradable materials.
Polymers have recently been making media headlines in various negative ways. To combat the negative view of those with no polymer experience, sustainable and biodegradable materials are constantly being researched. Shape-memory polymers, also known as SMPs, are a type of polymer material that is being extensively researched in the polymer industry. These SMPs can exhibit a change in shape because of an external stimulus. SMPs that are biodegradable or biocompatible are used extensively in medical applications. The use of biodegradable SMPs in the medical field has also led to research of the material in other applications. The following categories used to describe SMPs are discussed: net points, composition, stimulus, and shape-memory function. The addition of fillers or additives to the polymer matrix makes the SMP a polymer composite. Currently, biodegradable fillers are at the forefront of research because of the demand for sustainability. Common biodegradable fillers or fibers used in polymer composites are discussed in this chapter including Cordenka, hemp, and flax. Some other nonbiodegradable fillers commonly used in polymer composites are evaluated including clay, carbon nanotubes, bioactive glass, and Kevlar. The polymer and filler phase differences will be evaluated in this chapter. The recent advances in biodegradable shape-memory polymers and composites will provide a more positive perspective of the polymer industry and help to attain a more sustainable future.
The fast biodegradation rate and inflammability of polybutylene succinate (PBS) severely restrict its applications in many areas. To solve the above problems and broaden its applications, herein, a halogen‐free flame retardant (CP‐lignin) based on lignin was successfully synthesized. After adding 30 wt% CP‐lignin into PBS, the peak heat release rate and total heat release of PBS are remarkably reduced by 27 and 31%, respectively. Additionally, the higher char yield was beneficial to improving the flame retardant properties of PBS. After adding 10 wt% CP‐lignin, the ratio of weight loss is reduced by about 33%, and the ratio of weight loss is decreased gradually as the CP‐lignin loading increases. This research provides a reasonably way to make full use of the lignin and to broaden the application of PBS. At the same time, it also provides a new idea for the production and preparation of completely biodegradable materials.
To achieve the goal of preparing in-situ microfibril composite (MFC), multiple strong shear flows were imposed on the melt of high density polyethylene (HDPE) /polystyrene (PS). During vibration injection molding (VIM), both phase morphology and crystalline structure show big difference from the common injection molding (CIM) samples. The PS phase would deform into ultrafine microfibrils and then absorbs the HDPE matrix to form shish-kebab super crystalline structure. The morphology analysis shows that when PS content increases, the size and morphology would change correspondingly. When PS content reaches some level, it would impair the mechanical performance. This work also analyzes the relationship between blending ratio with crystalline structure and explains the difference. These results provide a valuable insight into immiscible polymer systems under shearing field and have its industrial prospect in the future.
Biomedical applications of polymers require precise control of the solid-state structure, which is of particular interest for biodegradable copolymers. In this work, we evaluated the influence of crystallization conditions on the comonomer exclusion/inclusion balance of biodegradable poly (butylene succinate-ran-butylene adipate) (PBSA) isodimorphic random copolymers. Regardless of the crystallization conditions, the copolymers retain their isodimorphic character displaying a pseudo-eutectic behavior with crystallization in the entire composition range. This illustrates the thermodynamic nature of the isodimorphic behavior for PBSA random copolymers. However, depending on the composition, the crystallization conditions affect the exclusion/inclusion balance of the comonomers. Fast cooling favors BA inclusion inside the PBS crystals, whereas isothermal crystallization strongly limits it. PBA rich compositions behave differently. Both fast and slow crystallization formed the β-phase, whereas BS unit inclusion is favored independently of the cooling conditions. During Successive Self-nucleation and Annealing (SSA), the BA inclusion is intermediate between non-isothermal and isothermal conditions, while the crystalline structure of the PBA phase changes from -phase to the more stable -phase. We propose a simple crystallographic model to explain the changes in the unit cell dimension of the copolymers.
Cellulose‐ and lignin‐based fillers can significantly enhance the mechanical properties and flame retardancy of biomass polyesters, whereas complicated and high‐cost processes may be necessary for the extraction. Thus, we explored the direct use of eucommia residues (ERs), a plantation waste containing rich lignocellulosic substances (ca. 18% cellulose, 13% hemicellulose, and 35% lignin), to reinforce polyesters and improve their flame retardancy. With poly(butylene succinate) (PBS) as the polyester matrix, the ER could enhance the tensile and flexural modulus of polyester‐based composite by 87 and 72%, respectively, via a facile melt‐mixing method with 30 wt % ER. Such enhancements, accompanying cost reduction, came from the cellulose crystallinity and rigid chemical structure of lignin, along with the strong interaction between ER and PBS. Besides, the carbon residue of PBS/ER composites in the flame‐retardant study could maximally increase by 508%, benefited from the immense hex‐carbon rings of cellulose and lignin in ERs. The ER also reduced the peak heat release rate and total heat release of PBS by 43 and 20%, respectively. This work reduces the pressure from waste treatment, promotes the high‐value application of plantation lignocellulosic‐rich wastes in package plastics and membranes, and supports sustainable material development based on biomass multicomponents resources. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48543. Schematical illustration for the preparation of composites from poly(butylene succinate) and eucommia residues.
Degradation of short sisal fibres/Mater Bi-Y™ biocomposites during indoor burial experiments was analysed. Within the first month, water sorption was the main event followed by weight loss. Water sorption results demonstrated that composites absorbed less water than the matrix. The lower sorption capacity of composites was related to the presence of fibre–fibre and fibre–matrix (both of carbohydrate nature) interactions which delay the water intake and enhances the material stability. In soil burial, all materials followed the same degradation pattern. The amorphous nature of the matrix favoured the preferential removal of starch, which was the most bio-susceptible material, as observed by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Fibres seemed to play a secondary role in this process, as confirmed by the slight difference in weight loss between the matrix and composites (40 and 33wt.%, respectively). The drop in mechanical properties as a function of the exposure time was associated with the preferential loss of matrix and fibre components and the detriment of the fibre/matrix interface.
The use of hemp fibers as reinforcement in composite materials has increased in recent years as a response to the increasing demand for developing biodegradable, sustainable, and recyclable materials. Hemp fibers are found in the stem of the plant which makes them strong and stiff, a primary requirement for the reinforcement of composite materials. Themechanical properties of hemp fibers are comparable to those of glass fibers. However their biggest disadvantage is the variability in their properties. Composites made of hemp fibers with thermoplastic, thermoset, and biodegradable matrices have exhibited good mechanical properties. A number of hemp fiber surface treatments, used to improve the fiber/matrix interfacial bonding, have resulted in considerable improvements in the composites’ mechanical properties.
Biodegradable thermoplastic-based composites reinforced with kenaf fibers were prepared and characterized. Poly(lactic acid) (PLA) was selected as polymeric matrix. To improve PLA/fibers adhesion, low amount of a proper reactive coupling agent, obtained by grafting maleic anhydride onto PLA, was added during matrix/fibers melt mixing. Compared with uncompatibilized composites, this compatibilization strategy induces a strong interfacial adhesion and a pronounced improvement of the mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Composites of poly(L-lactide) (PLA) with hemp fibers (Cannabis sativa), prepared by batch mixing and plasticized with poly(ethylene glycol) (PEG; weight-average molecular weight = 600 g/mol), were examined by polarized optical microscopy, scanning electron microscopy, wide-angle X-ray scattering, differential scanning calorimetry, thermogravimetric analysis, and mechanical tests. The properties of both fully amorphous and semicrystalline samples of PLA/hemp and PLA–PEG/hemp composites were analyzed as a function of the fiber amount. The cold-crystallization kinetics of PLA in amorphous composites were investigated under isothermal conditions within the range of 70–130°C. For PLA/hemp samples, the bulk crystallization rate displayed a maximum near 110°C, whereas for plasticized samples, a higher and almost constant crystallization rate was observed over the entire temperature range, independently of the hemp amount. The kinetics were then analyzed on the basis of the Avrami model. The effect of fibers on the growth morphology of PLA spherulites, as well as the influence of the plasticizer on the melting behavior of PLA crystals and their reorganization during heating, was also examined. The thermogravimetric analysis of the composites, carried out in both nitrogen and air, showed that the degradation process of fiber-filled systems started earlier than that of plain PLA, independently of the presence of the plasticizer. Mechanical tests showed that the modulus of elasticity of the composites markedly increased with the hemp content, reaching 5.2 GPa in the case of crystallized PLA reinforced with 20 wt % hemp, whereas the elongation and stress at break decreased with an increasing amount of fiber for all examined systems. Plasticization with PEG did not improve the tensile properties of the composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 255–268, 2007
PLA and PCL based nanocomposites prepared by adding three different types of fumed silica were obtained by melt blending. Materials were characterized by means of Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Dynamic–Mechanical Thermal Analysis (DMTA).A good distribution of the fumed silica into both polymer matrices was observed. The highest thermo-mechanical improvements were reached by addition of the fumed silica with higher surface area. PLA and its nanocomposites were degraded in compost at 58 °C; at this temperature all samples presented a significant level of polymer degradation, but a certain protection action of silica towards PLA degradation was observed, whereas the addition of fumed silica did not show considerable influence on the degradation trend of PCL. These dissimilarities were attributed to the different degradation mechanism of the two polymers.Graphical abstract
Bast fibres are defined as those obtained from the outer cell layers of the stems of various plants. The fibres find use in textile applications and are increasingly being considered as reinforcements for polymer–matrix composites as they are perceived to be “sustainable”. The fibres are composed primarily of cellulose which potentially has a Young’s modulus of ∼140 GPa (being a value comparable with man-made aramid [Kevlar/Twaron] fibres). The plants which are currently attracting most interest are flax and hemp (in temperate climates) or jute and kenaf (in tropical climates). This review paper will consider the growth, harvesting and fibre separation techniques suitable to yield fibre of appropriate quality. The text will then address characterisation of the fibre as, unlike man-made fibres, the cross section is neither circular nor uniform along the length.
Bio-composites comprised of kenaf fiber reinforced polylactide are fabricated by carding followed by treatment with a 3-glycidoxypropyl trimethoxy silane and hot-pressing. The effects of the silane coupling agent on composite properties was highly beneficial leading to increased moduli and heat deflection temperatures as well as reduced water swelling. Swelling is found to increase with increasing kenaf loading levels but to decrease with increasing coupling agent concentrations. Mechanical properties of the bio-composites at tempertaures above the glass transition are vastly improved in comparison to the base PLA polymer. As little as 10 wt.% kenaf fiber in PLA provides a heat distortion temperature in excess of 140 °C when combined with the coupling agent. The thermal stability towards degradation is slightly decreased relative to the base PLA and the ash content is increased. Thermal properties such as the glass transition, melting temperature, and percent crystallinity of the matrix PLA are largely unaffected by incorporation into the composites. Evidence of successful reaction of the silane with the kenaf fibers is provided by FTIR and implied by decreased swelling in water. A prototypical automotive headliner is fabricated as a means of demonstrating the viability of the present bio-composites in real manufacturing processes.
Poly(butylene succinate) (PBS) filled kenaf bast fiber (KBF) composites were fabricated via compression molding. The effects of KBF loading on the flexural and impact properties of the composites were investigated for fiber loadings of 10–40 wt %. The optimum flexural strength of the composites was achieved at 30 wt % fiber loading. However, the flexural modulus of the composites kept increasing with increasing fiber loading. Increasing the fiber loading led to a drop in the impact strength of about 57.5–73.6%; this was due to the stiff nature of the KBF. The effect of the fiber length (5, 10, 15, and 20 mm) on the flexural and impact properties was investigated for the 30 wt % KBF loaded composites. The composites with 10-mm KBF showed the highest flexural and impact properties in comparison to the others. The inferior flexural and impact strength of the composites with 15- and 20-mm KBF could be attributed to the relatively longer fibers that underwent fiber attrition during compounding, which consequently led to the deterioration of the fiber. This was proven by analyses of the fiber length, diameter, and aspect ratio. The addition of maleated PBS as a compatibilizer resulted in the enhancement of the composite's flexural and impact properties due to the formation of better fiber–matrix interfacial adhesion. This was proven by scanning electron microscopy observations of the composites' fracture surfaces. The removal of unreacted maleic anhydride and dicumyl peroxide residuals from the compatibilizers led to better fiber–matrix interfacial adhesion and a slightly enhanced composite strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Composites obtained from biodegradable polymers and natural–organic fillers are attracting increasing interest, thanks to the environmental advantages they promise. On the other hand, the real biodegradation performance of a biodegradable polymer/natural organic filler composite should be assessed by performing specific biodegradation tests. These are often carried out under laboratory conditions, but more realistic conditions should be taken into account. In this work, a systematic study on the biodegradation of kenaf fiber-filled Mater-Bi® composites in different environments is presented, and some interesting parameters for the understanding of the optimum way to obtain a fast degradation of the composites can be extrapolated. In particular, it was found that the presence of the fibers, the environmental conditions, and the manufacturing procedures of the composites can significantly affect the biodegradation behavior. The results can be used to determine the most suitable disposal environments for biodegradation of Mater-Bi®-based wastes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
This research work has concerned a study on thermomechanical and crystallization properties of poly(lactic acid) (PLA) composites containing three different types of additives; namely: kenaf fiber (20 pph), Cloisite30B nanoclay (5 pph), and hexagonal boron nitrile (h‐BN; 5 pph). The composites were prepared using a twin screw extruder before molding. Crystallization behaviors of the various composites were also examined using a differential scanning calorimetry. By adding the additives, tensile modulus of the polymer composites increased, whereas their tensile strength and elongation values decreased as compared to those of the neat PLA. Heat distortion temperature (HDT) values of the materials slightly increased, for about 3–5°C. However, after annealing at 100°C, HDT values of the fabricated PLA composites rapidly increased with annealing time before reaching a plateau after 10 min. The HDT values of above 120°C were achieved when 20 pph kenaf fiber was used as an additive. The above results were in a good agreement with DSC thermograms of the composites, indicating that percentage crystallinity of the materials increased on annealing and crystallization rate of the PLA/kenaf system was the highest. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
We report the preparation of polybutylene succinate (PBS)/sisal-fiber (SF) composites. The effects of mixing temperature and of steam-explosion pretreatment of SFs on the mechanical properties of the composites were investigated, and the mechanism of action was studied by infrared spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy. The results indicate that as the mixing temperature increases, PBS flows better and can graft onto steam-exploded sisal fiber (SESF), the interfacial bond property between SESF and PBS improves, and the mechanical properties of the composites improve. The mechanical properties of the composites are maximal for a mixing temperature of 200°C. The results also demonstrate that the cellulose content and the specific fiber surface area can be increased by steam-explosion pretreatment, so that the mechanical properties of the composites can be improved. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers
PLA/hemp co-wrapped hybrid yarns were produced by wrapping PLA filaments around a core composed of a 400 twists/m and 25 tex hemp yarn (Cannabis sativa L) and 18 tex PLA filaments. The hemp content varied between 10 and 45 mass%, and the PLA wrapping density around the core was 150 and 250 turns/m. Composites were fabricated by compression moulding of 0/90 bidirectional prepregs, and characterised regarding porosity, mechanical strength and thermal properties by dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). Mechanical tests showed that the tensile and flexural strengths of the composites markedly increased with the fibre content, reaching 59.3 and 124.2 MPa when reinforced with 45 mass% fibre, which is approximately 2 and 3.3 times higher compared to neat PLA. Impact strength of the composites decreased initially up to 10 mass% fibre; while higher fibre loading (up to 45 mass%) caused an increase in impact strength up to 26.3 kJ/m2, an improvement of about 2 times higher compared to neat PLA. The composites made from the hybrid yarn with a wrapping density of 250 turns/m showed improvements in mechanical properties, due to the lower porosity. The fractured surfaces were investigated by scanning electron microscopy to study the fibre/matrix interface.
Cellulose fibre-reinforced poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) composites have become increasingly interesting with regard to their biodegradability and mechanical characteristics. The use of different matrices leads to variable composite characteristics. This study provides a comparison of the mechanical characteristics of compression-moulded 30 mass% lyocell and 40 mass% kenaf fibre-reinforced PLA and PHB. The results of the tensile tests showed that 30 mass% lyocell/PLA composites reached the highest tensile and bending strength with 89 and 148N/mm2, respectively. The highest Young’s modulus was also measured for 30 mass% lyocell/PLA with 9.3GPa, and the highest flexural modulus was measured for 40 mass% kenaf/PHB with 7.1GPa. By far, the best impact strength was determined for lyocell/PHB with 70kJ/m2, followed by lyocell/PLA with 52kJ/m2. The investigation of the Shore D hardness resulted in a higher value for the PLA matrix with 81.5. PHB achieved a hardness of 67.5. By adding fibres as reinforcement, the Shore D hardness increased up to 83.6 for lyocell/PLA and 73.1 for kenaf/PHB. Density measurements showed lower densities for the composites with higher fibre loads (kenaf/PLA and kenaf/PHB) in comparison to the theoretical density. This speaks for a higher proportion of air inclusion in the composites which could negatively affect the mechanical composite characteristics.
Biodegradable composite materials can be produced by the combination of biodegradable polymers and natural fibers. In this study, a new biodegradable composite of hemp fiber reinforced polylactic acid (PLA) was fabricated using the hot press method. Mechanical properties of composites with different fiber volume fractions were tested. The optimum fiber content was determined according to the test results. Effects of alkali treatment on the fiber surface morphology and the mechanical properties of the composites were investigated. Test results show that the composite with 40% volume fraction of alkali treated fiber has the best mechanical properties. The tensile strength, elastic modulus, and flexural strength of the composite with 40% treated fiber are 54.6 MPa, 8.5 Gpa, and 112.7 MPa respectively, which are much higher than those of PLA alone. The composites have lower densities, which were measured to be from 1.19 g/cm3 to 1.25 g/cm3. Specific strengths were also calculated. Surface morphologies of fiber and fracture surfaces of the composites were observed using the SEM method.
Plant fibre reinforced polyester using non-woven fibre mats were manufactured. Acetylated and coupling agent (γ- methacryloxypropyltrimethoxy silane) or titanate (neopentyl (diallyl) oxy tri (dioctyl) pyro-phosphate titanate) treated fibres were used. The results of biological tests on the fibre composites was found to be dependent on fibre treatment. Acetylation exhibited superior bio-resistance followed by silane, as well as cast resin and glass fibre composites in soil tests up to 12 months exposure. Titanate and unmodified fibre composites exhibited high tensile and impact properties losses.
A biocomposite was originally fabricated with biodegradable polymer PBS and jute fibre, and the effects of fibre surface modification on characteristics of jute fibre and mechanical properties of the biocomposite were evaluated in this paper. The experimental results show that surface modification can remove surface impurities and reduce diameter of jute fibres. Regarding the mechanical properties of biocomposites, it is observed that the biocomposites with jute fibres treated by 2% NaOH, 2+5% NaOH or coupling agent, respectively, an optimum in mechanical properties can obtain at fibre content of 20wt.%, which exhibit an obvious enhancement in mechanical strength and modulus compared to the ones with untreated jute fibre. Furthermore, surface modification also exhibits less effects on flexural properties compared to tensile properties and more on flexural or tensile modulus than on the strength.
The present paper focuses on short flax fibre reinforced composites based on polyhydroxybutyrate (PHB) and its copolymer with hydroxyvalerate (HV). The effect of the fibre and copolymer content on the mechanical properties of the composites is being discussed. Furthermore, the influence of manufacturing method (compression moulding of non-woven mats and injection moulding of short fibre compounds) and processing conditions (cooling temperature and annealing) on the mechanical properties of the composites is being investigated. Finally, the biodegradability of the aforementioned composites expressed as weight, stiffness and strength loss as a function of burrier time is presented on the example of injection moulded flax/PHB/HV composites. It can be concluded that the addition of flax fibres along with controlled processing conditions seems to be a convenient way of toughening of the PHB matrix. Composites manufactured through injection moulding exhibited lower impact strength than those manufactured through compression moulding. Based on the biodegradation study of PHB/HV composites it can be concluded that the tensile properties drop significantly in the initial stage of degradation. The drop in tensile properties is more gradual in the later stages of biodegradation.
A series of nanocomposites consisted of poly(butylene succinate) (PBSu) and fumed silica nanoparticles (SiO2) were prepared using the in situ polymerization technique. The amount of SiO2 used directly affected the final molecular weight of the prepared polyesters. At a low SiO2 content (0.5wt.%) the molecular weight obtained was higher compared to neat PBSu, however at higher concentrations this was gradually reduced. The melting point of the matrix remained unaffected by the addition of the nanoparticles, in contrast to the crystallinity, which was dramatically reduced at higher SiO2 contents. This was mainly due to the extended branching and cross-linking reactions that took place between the carboxylic end groups of PBSu and the surface silanols of the nanoparticles. Thermal degradation of the PBSu/SiO2 nanocomposites was studied by determining theirs mass loss during heating. From the variations of the activation energies, calculated from the thermogravimetric curves, it was clear that nanocomposites containing 1wt.% SiO2 content had a higher activation energy compared to pure PBSu, indicating that the addition of the nanoparticles could slightly increase the thermal stability of the matrix. However, in PBSu/SiO2 nanocomposite containing 5wt.% SiO2 the activation energy was smaller. This phenomenon should be attributed to the existence of extended branched and cross-linked macromolecules, which reduce the thermal stability of PBSu, rather than to the addition of fumed silica nanoparticles.
Four blends of poly(hydroxybutyrate) (PHB) and poly(butylene succinate) (PBSU), both biodegradable semicrystalline polyesters, were prepared with the ratio of PHB/PBSU ranging from 80/20 to 20/80 by co-dissolving the two polyesters in N,N-dimethylformamide and casting the mixture. Differential scanning calorimetry (DSC) and optical microscopy (OM) were used to probe the miscibility of PHB/PBSU blends. Experimental results indicated that PHB showed some limited miscibility with PBSU for PHB/PBSU 20/80 blend as evidenced by the small change in the glass transition temperature and the depression of the equilibrium melting point temperature of the high melting point component PHB. However, PHB showed immiscibility with PBSU for the other three blends as shown by the existence of unchanged composition independent glass transition temperature and the biphasic melt. Nonisothermal crystallization of PHB/PBSU blends was investigated by DSC using various cooling rates from 2.5 to 10°C/min. During the nonisothermal crystallization, despite the cooling rates used two crystallization peak temperatures were found for PHB/PBSU 40/60 and 60/40 blends, corresponding to the crystallization of PHB and PBSU, respectively, whereas only one crystallization peak temperature was observed for PHB/PBSU 80/20 and 20/80 blends. However, it was found that after the nonisothermal crystallization the crystals of PHB and PBSU actually co-existed in PHB/PBSU 80/20 and 20/80 blends from the two melting endotherms observed in the subsequent DSC melting traces, corresponding to the melting of PHB and PBSU crystals, respectively. The subsequent melting behavior was also studied after the nonisothermal crystallization. In some cases, double melting behavior was found for both PHB and PBSU, which was influenced by the cooling rates used and the blend composition.
Acacia mangiumwood flour (AMWF)–polypropylene (PP) composites were produced at different filler loading (20, 30, 40, and 50 w/w) and mesh no. (35, 60, 80, and 100 mesh). The AMWF–PP composites (using unmodified or modified wood flour) were compounded using a Haake Rheodrive 500 twin screw compounder. The mechanical and water absorption (WA) properties of modified (only at mesh no. 100) and unmodified AMWF–PP composites were investigated. Increase in the mesh number (35–100) of the unmodified AMWF showed increased flexural and impact properties. Flexural modulus exhibited higher properties as the filler loading increased (20–50). However, flexural and impact strength showed the opposite phenomenon. Water absorption and thickness swelling increased as the mesh number and filler loading increased. This has been attributed to the presence of hydrophilic hydroxyl groups of the filler. Modified AMWF–PP composites exhibited higher mechanical properties and good water resistance when compared to unmodified AMWF–PP composites at all values of filler loading. The evidence of the failure mechanism (from impact strength) of the filler–matrix interface was analyzed using scanning electron microscope.
The effects of fibre loadings (10−40 wt.%) on mechanical properties, water absorption and dimensional stability of poly(butylene succinate)-filled kenaf bast fibre composites were investigated. The flexural strength and modulus of the composites increased with increasing fibre loading, while the impact strength of the composites decreased with increasing fibre loading. The higher the KBF loading was the higher absorption rate, equilibrium moisture content and the poorer dimensional stability of the composites. The poor retention and recovery of the composites from effect of water absorption were reflected by the poor flexural properties of the wet and re-dried composites after exposed to 90 days' water immersion.
In the present study poly(propylene sebacate) (PPSeb) nanocomposites containing 2 wt% of either fumed silica nanoparticles (SiO2), multiwalled carbon nanotubes (MWCNTs), or montmorillonite (MMT) were prepared by in situ polymerization. TEM micrographs confirmed that the dispersion of the nanoparticles was homogeneous in the PPSeb matrix, although some small agglomerates were observed, mainly in SiO2 nanocomposites. The tensile strength and Young’s moduli were significantly increased in nanocomposites due to the addition of nanoparticles. The reinforcement effect of nanoparticles was also established through Dynamic Themomechanical analysis (DMA). Mass loss measurements showed that, when compared to neat PPSeb, the presence of nanoparticles results in reduced enzymatic hydrolysis rates. This is due to the hindering effect of nanoparticles on the action of the enzymes since the former reduce the available surface area for hydrolysis, but also due to the interactions taking place between nanoparticles and PPSeb matrix. The mechanism of enzymatic hydrolysis was investigated by molecular weight variation and LC-MS analysis of the soluble by-products. It was found that PPSeb and its nanocomposites have identical hydrolysis mechanisms; even thought nanocomposites have lower hydrolysis rates.
The aliphatic polyester Bionolle 3020 was combined with lignocellulosic fibers, namely, flax, hemp, and wood, to produce biodegradable composite materials. The effect of two fiber surface treatments, acetylation and propionylation, and the addition of maleic anhydride (MA)-grafted Bionolle 3001 as a compatibilizer on the fiber/matrix interfacial adhesion was studied. The compatibilizer was synthesized through a MA grafting reaction in the presence of dicumyl peroxide as an initiator. The composites' mechanical properties, water absorption, fracture morphology (scanning electron microscopy), and biodegradation were evaluated. Both the fiber treatments and the compatibilizer incorporation significantly improved the composites' tensile strength, whereas an important reduction in the water absorption was found with the addition of treated fibers. Moreover, fiber incorporation into the matrix increased its biodegradation rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4703–4710, 2006
Natural fiber composites were designed and optimized to achieve good mechanical properties and resistance to growth of living organisms. Composite materials were prepared from poly(lactic acid) (PLA) with flax fibers, where the flax fibers had been subjected to interstitial polymerization to replace the water in the cellulose fibers. Before polymerization, the flax fibers were extracted with sodium hydroxide and acetone to remove lignin, pectin, and waxes from the cellulose. Differential scanning calorimetry was used to study the crystallization and melting of the composites as compared with pure PLA. The surface wetting of the fibers and morphology of the composites were studied by scanning electron microscopy and optical microscopy. Mechanical properties were studied using dynamic mechanical analysis. The influence of the interstitial polymerization on the dynamic storage modulus was found to be significant. The composites of polymerization treated flax, with acetone washed fibers, had higher storage moduli than the unwashed fiber composites, which suggested adhesion between flax fibers, and the matrix was improved by the treatments. The composites were subjected to moist environmental conditions to test for development of mold and fungi, and the acetone washed polymerization treated flax composites were resistant to these growths. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Biodegradable homopolyesters such as poly(butylene succinate) (PBSU) and poly(butylene adipate) (PBAD) and copolyesters such as poly(butylene succinate-co-butylene adipate) (PBSA) were synthesized, respectively, from succinic acid (SA) and adipic acid (AA) with 1,4-butanediol through a two-step process of esterification and deglycolization. The polyester compositions and physical properties of both homopolyesters and copolyesters were investigated by 1H– and 13C–NMR, DSC, GPC, WAXD, and optical polarizing microscopy. The melting point (Tm) of these copolyesters decreased gradually as the contents of butylene adipate increased and the glass-transition temperature (Tg) of these copolyesters decreased linearly as the contents of the adipoyl unit increased. PBSA copolyesters showed two types of XRD patterns of PBSU and PBAD homopolyesters. Furthermore, the biodegradation and hydrolytic degradation of the high molecular weight PBSU homopolyester, PBAD homopolyester, and PBSA copolyesters were investigated in the composting soil and NH4Cl aqueous solutions at a pH level of 10.6. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2808–2826, 2001
In this work, mechanical properties of chemically treated random short fibre and aligned long hemp fibre reinforced PLA composites were investigated over a range of fibre content (0–40 wt.%). It was found that tensile strength, Young’s modulus and impact strength of short hemp fibre reinforced PLA composites increased with increased fibre content. Alkali and silane fibre treatments were found to improve tensile and impact properties which appears to be due to good fibre/matrix adhesion and increased matrix crystallinity. A 30 wt.% alkali treated fibre reinforced PLA composite (PLA/ALK) with a tensile strength of 75.5 MPa, Young’s modulus of 8.18 GPa and impact strength of 2.64 kJ/m2 was found to be the best. However, plane-strain fracture toughness and strain energy release rate decreased with increased fibre content. The mechanical properties of the PLA/ALK composites were increased further due to alignment of long fibres.
Poly(butylene succinate) (PBS)/jute composites were prepared, and the effects of fibre content, diameter, surface modification and arrangement forms on the biodegradability were evaluated by compost-soil burial test. The weight losses of PBS/jute composites are higher than that of pure PBS film and bulk jute fibre, and decreased with increasing fibre content. The weight loss of PBS/10% jute composite after 180 days is 62.5%. In the case of the effect of fibre diameter, the weight loss is found to decrease with decreasing fibre diameter. For the effect of fibre surface modification, the order of higher weight loss is PBS/untreated jute > PBS/alkali treated jute > PBS/coupling agent treated jute. Furthermore, the composite of PBS/woven fabric has the highest weigh loss, followed by that of PBS/nonwoven fabric and PBS/bulk jute fibre, respectively.
Natural fiber reinforced composites is an emerging area in polymer science. These natural fibers are low cost fibers with low density and high specific properties. These are biodegradable and non-abrasive. The natural fiber composites offer specific properties comparable to those of conventional fiber composites. However, in development of these composites, the incompatibility of the fibers and poor resistance to moisture often reduce the potential of natural fibers and these draw backs become critical issue. This review presents the reported work on natural fiber reinforced composites with special reference to the type of fibers, matrix polymers, treatment of fibers and fiber-matrix interface. © 1999 John Wiley & Sons, Inc. Adv in Polymer Techn 18: 351–363, 1999
This paper investigates and compares the performances of polylactic acid (PLA)/kenaf (PLA-K) and PLA/rice husk (PLA-RH) composites
in terms of biodegradability, mechanical and thermal properties. Composites with natural fiber weight content of 20% with
fiber sizes of less than 100μm were produced for testing and characterization. A twin-screw extrusion was used to compound
PLA and natural fibers, and extruded composites were injection molded to test samples. Flexural and Izod impact test, TGA,
soil burial test and SEM were used to investigate properties. All results were compared to a pure PLA matrix sample. The flexural
modulus of the PLA increased with the addition of natural fibers, while the flexural strength decreased. The highest impact
strength (34Jm−1), flexural modulus (4.5GPa) and flexural strength (90MPa) were obtained for the composite made of PLA/kenaf (PLA-K), which
means kenaf natural fibers are potential to be used as an alternative filler to enhance mechanical properties. On the other
hand PLA-RH composite exhibits lower mechanical properties. The impact strength of PLA has decreased when filled with natural
fibers; this decrease is more pronounced in the PLA-RH composite. In terms of thermal stability it has been found that the
addition of natural fibers decreased the thermal stability of virgin PLA and the decrement was more prominent in the PLA-RH
composite. Biodegradability of the composites slightly increased and reached 1.2 and 0.8% for PLA-K and PLA-RH respectively
for a period of 90days. SEM micrographs showed poor interfacial between the polymer matrix and natural fibers.
KeywordsPolylactic acid (PLA)-Natural fibers-Environmental degradation-Mechanical properties-Thermal properties
Two models have been developed which predict the crack initiation energy, notched impact strength and unnotched impact strength
of fibre composites. One is applicable to composites containing short fibres and the other to composites containing long fibres.
Data obtained with randomly oriented short fibre composites were consistent with the one model. The other model has been verified
using composites containing uniaxially oriented long fibres and long fibres oriented randomly in a plane. The success of the
model demonstrates that the high notched impact strength with long fibres is due to the redistribution of stress away from
the stress concentrating notch, the extra stress that can be held by the fibre relative to the matrix and the work required
to pull fibres out of the matrix during crack propagation. The parameters which have been shown to control the fracture energy
are composite modulus, fibre length, fibre volume fraction, effective fibre diameter, fibre tensile strength and the coefficient
of friction during fibre pull-out from the matrix. The matrix toughness on the other hand usually has no effect at all for
composites containing fibres randomly oriented in two dimensions and only a minor effect in exceptional cases. The shear strength
of the fibre-matrix bond has only an indirect effect in that it controls the number of fibres which pull out rather than fracture.
Poly(alkylene succinates) were synthesized from succinic acid and aliphatic diols with 2 to 4 methylene groups by melt polycondensation. DSC, 1H NMR, WAXD and molecular weight measurements were used to characterise the polymers. Biodegradability studies of polyesters with the same average molecular weight, included enzymatic hydrolysis for several days using Rhizopus delemar lipase at pH 7.2 and 30 °C. DSC traces of biodegraded polyesters revealed that hydrolysis affected mainly the amorphous material. For all polyesters an increase in glass transition, melting point and heat of fusion was recorded. In the first days of enzymatic hydrolysis, fast rates of mass loss were observed accompanied by a rapid reduction of intrinsic viscosity and molecular weight, thus indicating a mixed endo- and exo-type hydrolysis mechanism. Afterwards, it turned to an exo-type mechanism, taking place in the crystalline phase, since after 15–25 days of enzymatic hydrolysis molecular weight was stabilized, while mass loss kept on decreasing though in a slower rate. End-group analysis revealed that carboxyl and hydroxyl groups increased due to ester bonds' scission. The biodegradation rates of the polymers decreased following the order PPSu > PESu ≥ PBSu and it was attributed to the lower crystallinity of PPSu compared to other polyesters, rather than to differences in chemical structure. Finally, a simple theoretical kinetic model was developed and Michaelis–Menten parameters were estimated.
Cotton linters were partially hydrolyzed in dilute acid and the morphology of remaining macrofibrils was studied with scanning electron microscopy (SEM) under various magnifications. The crystalline region in cellulose is composed of microfibril bundles instead of separated microfibrils. These microfibril bundles in the macrofibrils were exposed by removing amorphous cellulose on and near the surface of the macrofibers. XRD suggests that the microfibril bundles have diameters of 20–30 nm. Cellulose apparent crystallinity was not altered by hydrolysis, as indicated by XRD and NMR results. These facts suggest that amorphous cellulose in the bulk (not on the surface) is not accessible to hydrolysis and that microfibril bundles are hydrolyzed through a surface reaction process. The observed agglomerization of macrofibers could be the result of the high surface potential from the remaining microfibrils or acid catalyzed intermolecular surface dehydration between macrofibrils.
Micro-Raman Spectroscopy (MRS) has been used to measure the load transfer in short-fiber, high-modulus/epoxy composites as a function of angle to the loading direction, and to monitor strain concentrations in short-fiber composites due to fiber/fiber interactions. Toray M40B PAN-based carbon fibers were tested with sized, unsized, elastomer-treated surfaces. The matrix was Shell Epon 828 cured with TETA. It was found that incremental load transfer to the fibers compared well with theory. It was also found that the maximum strain transfer rate did not depend on the angle of orientation. The interface was found to change the strain concentration factors, with a noticeable decrease in the strain concentration factors observed for a weaker, more brittle interface. The strain concentration results were used to modify an existing model of composite strength.
Composites of isotactic polypropylene (PP) with Hemp fibres (Cannabis sativa), functionalized by means of melt grafting reactions with glycidyl methacrylate (GMA) and prepared by batch mixing, were examined. Either the modification of fibres (Hemp-GMA) and polyolefin matrix (PP-g-GMA), as well as the addition of various compatibilizers (PP-g-GMA, SEBS, SEBS-g-GMA) were carried out to improve the fibre–matrix interactions. The modified components and their composites were characterised by FT-IR analysis, POM and SEM microscopy, RX, DSC, TGA and mechanical tests. The properties of binary (PP/Hemp, PP/Hemp-GMA, PP-g-GMA/Hemp) and ternary (PP/Hemp/compatibilizer) composites were analysed as a function of the fibre amount and compatibilizer content. All modified composites showed improved fibre dispersion in the polyolefin matrix and higher interfacial adhesion when compared to the unmodified system (PP/Hemp) as a consequence of chemical bonding between fibre and polymer. The thermal stability and phase behaviour of the composites resulted to be largely affected by the fibre and matrix modification. Changes in the spherulitic morphology and crystallisation behaviour of PP were observed in the composites due to the nucleating effect of Hemp fibres. Moreover, a marked increase of PP isothermal crystallisation rate (in the range 120–138 °C) was recorded with increasing the Hemp-GMA content. All composites displayed higher tensile modulus (about 2.9 GPa) and lower elongation at break as compared to plain PP; compatibilization with PP-g-GMA (10 phr) resulted in an increased stiffness of the composites as consequence of an improved fibre–matrix interfacial adhesion.
The focus in this work has been to study if natural fibres can be used as reinforcement in polymers based on renewable raw materials. The materials have been flax fibres and polylactic acid (PLA). PLA is a thermoplastic polymer made from lactic acid and has mainly been used for biodegradable products, such as plastic bags and planting cups, but in principle PLA can also be used as a matrix material in composites. Because of the brittle nature of PLA triacetin was tested as plasticizer for PLA and PLA/flax composites in order to improve the impact properties. The studied composite materials were manufactured with a twin-screw extruder having a flax fibre content of 30 and 40 wt.%. The extruded compound was compression moulded to test samples. The processing and material properties have been studied and compared to the more commonly used polypropylene flax fibre composites (PP/flax). Preliminary results show that the mechanical properties of PLA and flax fibre composites are promising. The composite strength is about 50% better compared to similar PP/flax fibre composites, which are used today in many automotive panels. The addition of plasticizer does not show any positive effect on the impact strength of the composites. The study of interfacial adhesion shows that adhesion needs to be improved to optimise the mechanical properties of the PLA/flax composites. The PLA/flax composites did not show any difficulties in the extrusion and compression moulding processes and they can be processed in a similar way as PP based composites.
This study investigated the biodegradability of PBS and bio-flour, which is a poly(butylene succinate) (PBS) bio-composite filled with rice-husk flour (RHF) reinforcing, in natural and aerobic compost soil. The percentage weight loss and the reduction in mechanical properties of PBS and the bio-composites in the compost soil burial test were significantly greater than those in the natural soil burial test. These results were supported by degraded surface of PBS and bio-composites observed through morphological study and the total colony count of natural soil was lower than that of compost soil. The biodegradability of the bio-composites was enhanced with increasing bio-flour content because the bio-flour is easily attacked by microorganisms. As the biodegradability test progressed over time up to 80 days, the molecular weight of PBS decreased in the soil burial test. We confirmed by attenuated total reflectance (FTIR–ATR) analyser that the chemical structures of PBS and the bio-composites were changed after the compost burial test. The glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), heat of fusion (ΔHf) and heat of crystallization (ΔHc) of the natural and composted soil tested PBS were investigated using differential scanning calorimetry (DSC). From the results, we concluded that use of these bio-composites will reduce the environmental problems associated with waste pollution and the study findings support the predicted application of bio-composites as “green-composites” or “eco-materials”.
The interest for biodegradable polymers and natural fibre-reinforced polymers has recently grown because of increasing environmental concerns. But the impact properties of bast fibres reinforced polymers cannot reach the levels of traditional fibre-reinforced polymers.PLA (polylactic acid) was reinforced with Cordenka rayon fibres and flax fibres, respectively. The mechanical properties of these composites which are examples for completely biodegradable composites were tested and compared. The samples were produced using injection moulding. The highest impact strength (72 kJ/m2) and tensile strength (58 MPa) were found for Cordenka reinforced PLA at a fibre-mass proportion of 30%. The highest Young’s modulus (6.31 GPa) was found for the composite made of PLA and flax. A poor adhesion between the matrix and the fibres was shown for both composites using SEM. The promising impact properties of the presented PLA/Cordenka composites show their potential as an alternative to traditional composites.
Up to now the reinforcing potential of hemp fibres has not been exhausted, as the fibres are bundled and, therefore, a homogenous distribution of fibres and matrix has not been possible. In the present study the fibre bundles used for the composites were degummed by means of biological processes and steam explosion. The degummed fibres, separated into single cells, were integrated into the brittle poly (3-hydroxybutyrate-co-hydroxyvalerate) matrix and into the ductile co-polyester amide matrix by means of a co-rotating twinscrew extruder. Composites with a fibre volume fraction of up to 42% could be achieved. The tensile strength of the ductile material was almost doubled by the reinforcement with 27% of fibres to 30 MPa, the E-modulus was quadrupled to 3.5 GPa. No improvement of the tensile strength of the brittle matrix could be achieved, whereas its E-modulus was increased up to 6 GPa. As the composite behaviour is determined by the matrix, the fibre reinforcement is accompanied by a reduction of the impact strength.
Polyesters based on succinic acid and respective aliphatic diols, with 2–4 methylene groups were synthesized by melt polycondensation. Crystallization and melting behaviour of samples having the same molecular weight were studied. The odd–even effect was observed for the melting temperatures of these polymers. Poly(propylene succinate) exhibited the slower crystallization rates and lower degree of crystallinity, among these polyesters. In contrast poly(butylene succinate) showed the faster crystallization rates and higher degree of crystallinity. Multiple melting of the isothermally crystallized samples was attributed to partial melting re-crystallization and re-melting, as was revealed by MTDSC measurements and observations at fast DSC heating scans. The equilibrium melting points were found to be 114, 133.5 and 58 °C for PESu, PBSu and PPSu respectively. Also, the corresponding values for enthalpy of fusion were 180, 210 and 140 J/g. Spherulitic growth rates were analysed and the regime transition of PESu and PBSu was studied.
Two aliphatic polyesters that consisted from succinic acid, ethylene glycol and butylene glycol, —poly(ethylene succinate) (PESu) and poly(butylene succinate) (PBSu)—, were prepared by melt polycondensation process in a glass batch reactor. These polyesters were characterized by DSC, 1H NMR and molecular weight distribution. Their number average molecular weight is almost identical in both polyesters, close to 7000 g/mol, as well as their carboxyl end groups (80 eq/106 g). From TG and Differential TG (DTG) thermograms it was found that the decomposition step appears at a temperature 399 °C for PBSu and 413 °C for PESu. This is an indication that PESu is more stable than PBSu and that chemical structure plays an important role in the thermal decomposition process. In both polyesters degradation takes place in two stages, the first that corresponds to a very small mass loss, and the second at elevated temperatures being the main degradation stage. The two stages are attributed to different decomposition mechanisms as is verified from the values of activation energy determined with iso-conversional methods of Ozawa, Flyn, Wall and Friedman. The first mechanism that takes place at low temperatures, is auto-catalysis with activation energy E = 128 and E = 182 kJ/mol and reaction order n = 0.75 and 1.84 for PBSu and PESu, respectively. The second mechanism is nth-order reaction with E = 189 and 256 kJ/mol and reaction order n = 0.68 and 0.96 for PBSu and PESu, respectively, as they were calculated from the fitting of experimental results.
Composites of an aliphatic polyester (Bionolle) with natural flax fibres are prepared by batch mixing. The effect of processing conditions on fibre length distribution and the dependence of the composite mechanical properties on fibre content are investigated. The tensile modulus changes with fibre content according to the modified rule-of-mixture equation, with a fibre orientation efficiency factor η0=0.194. The strength of Bionolle/flax composites tends to decrease with fibre loading, showing that there is no adhesion between matrix and fibres. With the aim to improve fibre–matrix adhesion, surface chemically modified flax fibres are also tested as reinforcing agents. A 30% strength increase is observed when natural fibres (25 vol%) are substituted by fibres containing acetate groups. No significant strength changes are observed in composites containing fibres with valerate groups or polyethylene glycol chains grafted at the surface.
FAO Global Workshop: Bast Fibrous Plants for Healthy Life, Banja Luka, Bosnia-Herzegovina, 24-28 October 2004 Composite materials reinforced with natural fibres, such as flax, hemp, kenaf and jute, are gaining increasing importance in automotive, aerospace, packaging and other industrial applications due to their lighter weight, competitive specific strength and stiffness, improved energy recovery, carbon dioxide sequestration, ease and flexibility of manufacturing and environmental friendliness besides the benefit of the renewable sources of bast fibres. The market scenario for composite applications is changing due to the introduction of newer biodegradable polymers such as PLA synthesized from corn, development of composite making techniques and new stringent environmental laws requiring improved recyclability or biodegradability for industrial applications where stress bearing capacities and micro-mechanical failures dictate serviceability. Bast fibre reinforced composites, made from biodegradable polymer, will have to compete with conventional composites in terms of their mechanical behaviour. Bio-composites, in which natural fibres such as kenaf, jute, flax, hemp, sisal, corn stalk, bagasse or even grass are embedded in a biodegradable matrix, made as bioplastics from soybean, corn and sugar, have opened up new possibilities for applications in automotive and building projects. Obviously new approaches to research and development will be required to assess their mechanical properties and also their commercial competitiveness against petroleum based products. This paper will review the newer products and techniques that can improve the properties of bast fibre based composites as well as potential applications which can increase their market share
Studies of solid-state structures under different crystallization conditions, melting behavior, and crystal growth kinetics are reported for biodegradable aliphatic poly(butylene succinate) (PBS) and its random copolyesters of poly(butylene succinate-co-14 mol %ethylene succinate) [P(BS-co-14 mol %ES)] and poly(butylene succinate-co-15 mol %hexamethylene succinate) [P(BS-co-15 mol %HS)]. The crystal structures of two copolyesters determined by wide-angle X-ray diffraction (WAXD) are the same as that of the PBS homopolymer, suggesting that the second comonomers ES or HS units are excluded from the crystalline core and are in an amorphous state. The further investigations on the crystalline and amorphous phase structures and sizes by small-angle X-ray scattering (SAXS) method have provided quantitative evidence that the existence of second comonomers increases the amorphous thickness of copolyesters but that the influences of comonomers on the lamellar crystal structure and size of copolyesters are complicated. The origin of the complexity and its influences on the equilibrium melting temperature T(m)(0) of copolyester are discussed in the present paper. Gibbs-Thomson and Hoffman-Weeks equations were applied for the determination of T(m)(0) of PBS, P(BS-co-14 mol %ES), and P(BS-co-15 mol %HS)-three samples. Two equations gave different T(m)(0) values for each sample. On the basis of the Gibbs-Thomson equation, the P(BS-co-15 mol %HS) copolyester has the same T(m)(0) value as that of the PBS homopolymer, while the P(BS-co-14 mol %ES) copolyester has a lower one. This is due to the different influences of the second comonomers on the crystalline phase structure indicated by SAXS results, and the Gibbs-Thomson equation has been suggested to be more reliable. The crystal growth kinetics of the three samples was analyzed by using the secondary nucleation theory, and the influences of various parameters on the regime transition and nucleation constant were studied. Meanwhile some interrelations between regime transition temperature and melting behavior were found for the three samples.
Biodegradable polymers and bioactive ceramics are being combined in a variety of composite materials for tissue engineering scaffolds. Materials and fabrication routes for three-dimensional (3D) scaffolds with interconnected high porosities suitable for bone tissue engineering are reviewed. Different polymer and ceramic compositions applied and their impact on biodegradability and bioactivity of the scaffolds are discussed, including in vitro and in vivo assessments. The mechanical properties of today's available porous scaffolds are analyzed in detail, revealing insufficient elastic stiffness and compressive strength compared to human bone. Further challenges in scaffold fabrication for tissue engineering such as biomolecules incorporation, surface functionalization and 3D scaffold characterization are discussed, giving possible solution strategies. Stem cell incorporation into scaffolds as a future trend is addressed shortly, highlighting the immense potential for creating next-generation synthetic/living composite biomaterials that feature high adaptiveness to the biological environment.