Article

Effect of moisture content on mechanical properties, thermal and structural stability and extruded texture of poly (vinyl chloride)/wood sawdust composites

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Abstract

Mechanical properties and thermal and structural changes of poly(vinyl chloride) (PVC)/wood sawdust composites were assessed with respect to the effect of moisture content, varying from 0.33 to 3.00 % by weight in the composite, for three different wood sawdust contents. The swell ratio and texture characteristics of the composite extrudates were also evaluated. Unique explanations were given to describe changes in the composite properties in terms of molecular interactions between PVC, cellulosic sawdust and moisture, such as dipole–dipole interactions, interfacial defects and bonding, fibre swelling, and moisture evaporation. The results suggest that at low moisture content the tensile modulus decreased and elongation at break of the composites increased with moisture content, the effect being reversed for high moisture content. Tensile strength decreased with increasing moisture content up to 1–2 %, and then unexpectedly increased at higher moisture contents. The effect of moisture content on flexural properties of the composite was similar to that on tensile properties. Impact strength of the composites was considerably improved with moisture content at low sawdust contents (16.7 wt%), and was independent of the moisture content at higher sawdust contents (28.6 and 37.5 wt%). A decrease in decomposition temperature with an increase in polyene content was evidenced with increasing moisture content, while the glass transition temperature did not change with varying moisture content. The extrudate swell ratio increased with the shear rate but remained unaffected by moisture content. The bubbling and peeling-off in the composite extrudate occurred as a result of the evaporation of water molecules and the application of a high shear rate. Copyright © 2004 Society of Chemical Industry

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... In general, there are not many studies reporting changes of fiber's mechanical properties with immersion. Some studies report that mechanical properties deteriorate with immersion, which is suggested to occur due to degradation of polymer (64,70,71). However, other studies have reported increases of the Young's modulus (64,71), tensile strength (64,70), elongation at break (69,70,72), or impact energy (73) with water immersion. ...
... Some studies report that mechanical properties deteriorate with immersion, which is suggested to occur due to degradation of polymer (64,70,71). However, other studies have reported increases of the Young's modulus (64,71), tensile strength (64,70), elongation at break (69,70,72), or impact energy (73) with water immersion. The plasticizing effect of water was suggested to be responsible for improvement of plasticity in those studies (70,73). ...
... Some studies report that mechanical properties deteriorate with immersion, which is suggested to occur due to degradation of polymer (64,70,71). However, other studies have reported increases of the Young's modulus (64,71), tensile strength (64,70), elongation at break (69,70,72), or impact energy (73) with water immersion. The plasticizing effect of water was suggested to be responsible for improvement of plasticity in those studies (70,73). ...
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... Hydroxyl groups behave as plasticizers among the PA chains and on the GF surface, thereby weakening the dipole-dipole interaction between chains and with GF [10,[38][39][40][41][42][43]. Moisture absorption increases PA chains' volume and mobility, thus weakening the entanglement and Polymer absorption properties proportionally increase with free volume in the composite [30,31], and hydrogen bonds with polar atoms in PA66 [32,33]. ...
... The recrystallization effect is more significant when PA66, exposed to MEG, dries at 100, 150, and 200 • C. As the drying temperature increases, and exposure time increases, the tensile strength also increases [24]. Hydroxyl groups behave as plasticizers among the PA chains and on the GF surface, thereby weakening the dipole-dipole interaction between chains and with GF [10,[38][39][40][41][42][43]. Moisture absorption increases PA chains' volume and mobility, thus weakening the entanglement and Figure 2. Hydrolysis of polyamide (adopted from Reference [37]). ...
... Hydroxyl groups behave as plasticizers among the PA chains and on the GF surface, thereby weakening the dipole-dipole interaction between chains and with GF [10,[38][39][40][41][42][43]. Moisture absorption increases PA chains' volume and mobility, thus weakening the entanglement and bonding between the molecules [37,44,45]. ...
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... Graphical plots of weight gained-immersion time and percent water absorption-immersion time for all the composites were produced and utilized to study the water absorption behaviour. The mechanism of water diffusion into the composites was studied by analysing the slope and intercepts of the water absorption graphs plotted by using the relations 2 and 3 as described by Sombastsompop and Chaochanchaikul [14] M ...
... This situation, which is classified also as Fickian diffusion, is called as 'Less Fickian' behavior [23]. These three cases of diffusion can be distinguished theoretically by the shape of the sorption curve [14] and on which basis the graph presented in Figure 7 was plotted. All types of water transport discussed above are presented in Table 1 for HDPE, EVA and HDPE/Silica composites with the coefficient, n and the intercept, k Figure 7 shows the diffusion curve fittings of experimental data for 2 wt%, 4 wt%, 6 wt% , 8 wt% and 10 wt% silica reinforcements with constant 0.3 wt% titania for the developed composites. ...
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... loss in these composite is less due to very low moisture uptake and improved interface between resin and the reinforcement. The decrease in mechanical properties with an increase in moisture content may be caused by the formation of hydrogen bonds between water molecules and cellulose fibers Sombatsompop & Chaochanchaikul, 2004). Natural fibers are generally hydrophilic in nature due to the presence of hydroxyl groups (-OH) in the fiber structure, resulting in the formation of a large number of hydrogen bonds between the cellulose and polymer macromolecules (Sombatsompop & Chaochanchaikul, 2004). ...
... The decrease in mechanical properties with an increase in moisture content may be caused by the formation of hydrogen bonds between water molecules and cellulose fibers Sombatsompop & Chaochanchaikul, 2004). Natural fibers are generally hydrophilic in nature due to the presence of hydroxyl groups (-OH) in the fiber structure, resulting in the formation of a large number of hydrogen bonds between the cellulose and polymer macromolecules (Sombatsompop & Chaochanchaikul, 2004). Therefore, the natural fibers such as flax and jute tend to show low moisture resistance. ...
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... Incorporation of fillers in PVC composite formulations can also impact the properties of the composite (Titow 1984;Lutz and Dunkelberger 1992). The presence of wood particles has increased the glass transition temperature (T g ) value of PVC/wood composite due to rigid content of wood material (Sombatsompop and Chaochanchaikul 2004) whereas for PVC/bagasse composites there was no change in the T g of the composite (Saini et al. 2010). Natural fillers can also impact decomposition temperature (T d ), where, for example, PVC/wood composite T d was decreased with greater particle content due to wood thermal deterioration (Sombatsompop and Chaochanchaikul 2004). ...
... The presence of wood particles has increased the glass transition temperature (T g ) value of PVC/wood composite due to rigid content of wood material (Sombatsompop and Chaochanchaikul 2004) whereas for PVC/bagasse composites there was no change in the T g of the composite (Saini et al. 2010). Natural fillers can also impact decomposition temperature (T d ), where, for example, PVC/wood composite T d was decreased with greater particle content due to wood thermal deterioration (Sombatsompop and Chaochanchaikul 2004). In other studies, decomposition rates of PVC/wood composite during the first stage of decomposition were lower than those of virgin PVC (Badrina et al. 2013) whereas wood filler added to PVC accelerated the overall dehydrochlorination of PVC (Fang et al. 2012) or led to increased thermo-oxidative stability in oxidative induction time (OIT) testing (Farhadinejad et al., cited in Borysiak 2015). ...
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Polyvinyl chloride (PVC) was mixed with bamboo (Bambusa vulgaris) particle and additives by using PVC composite manufacturing system including initial dry blending with hot-cool mixing, followed by granulation via counter-rotating extrusion, and then consolidation by compression moulding to produce compression moulded board (CMB). The effects of different bamboo particle size (75 µm and 1 mm), bamboo particle loading (25 and 50% loading ratio), and differing processing lubricants content level (compositions 1 and 2) on the thermal stability of the composites were determined. Results show no significant trends in glass transition temperature (Tg) between dry blends, granules, and CMB, and between B. vulgaris particle loading at the respective processing steps. For samples with higher lubricant contents, the PVC Tg was observed to decrease up to 5 °C, possibly due to the reduced melt viscosity. The thermal decomposition temperature at 5% mass loss (T−5%) appeared to decrease from dry blend to CMB due to sample degradation on further processing at higher temperatures. The use of 50% B. vulgaris particle loading also reduced the T−5% values, assignable to bamboo particle degradation caused by the high processing temperatures. For oxidative induction time (OIT) testing, only granules and CMB from pure PVC composites system showed measurable oxidative times compared with OIT profiles of PVC/B. vulgaris composites system, suggestive of comparatively stabilized thermoplastic composites. This revealed that processing with bamboo particles does not contribute to degradation of PVC composites.
... Composites usually conform to Fickian diffusion profiles, but this fact is verified with the experimental data of the different composite compositions. The mechanism of water diffusion into the composites was studied by analysing the slope and intercepts of the water absorption graphs plotted by using the relations in Eq. (2) and (3) according to [12]. The experimental data were fitted to a logarithmic equation (Eq. 3) whose slope (n) helps determines the diffusion case. ...
... Chaochanchikul [12]. Upon fitting the experimental data into equation (3), the plot in Figure 8 is presented. ...
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Water uptake characteristics of epoxy matrix composites reinforced with green silica particles extracted from rice husk ash have been investigated. The composites were developed by incorporating the rice husk silica particles in the weight fractions of 0.5, 1, 2, 3, 4 and 6% in an epoxy resin using manual mixing and hand layup method. Water immersion test was used to evaluate the water absorption behaviour from which the water diffusion mechanisms of the developed composites were established. Results showed that the water uptake process appears to be diffusion controlled. The weight gained and percentage water absorption by all the composites increases with immersion time and increasing particle loading respectively. The highly filled samples showed higher water absorption which is largely due to agglomeration of rice husk silica particles. Parameters such as saturated moisture content, diffusion coefficient and sorption coefficient are dependent on filler content. The diffusion curve fitting analysis which evaluates the diffusion exponent (n) values showed that all the composites developed exhibited Less Fickian behaviour (also considered as Fickian diffusion mechanism). This implies that the water penetration rate is very much below the polymer chain relaxation rate.
... Further increment in percentage of water absorption was observed at day 65 where the increase for PVC/RH40 was the highest, which is 2.4% while virgin PVC has the lowest percentage at 0.3%. This is due to the incorporation of RH, which had increased the number of microvoids caused by the larger amount of poorly bonded area between hydrophilic RH and hydrophobic PVC matrix, resulting in higher water absorption (Sombatsompop and Chaochanchaikul, 2004). This is in agreement with the proposed water absorption mechanism proposed by Lin et al. (2002), Kiani et al. (2011), andRazavi-Nouri et al. (2006), in which the water molecules are diffused through capillary action into the gaps and flaws created at the interface of polymer matrix and fiber. ...
... It affected the kenaf fibres toby having low resistivity towards moisture due to the presence of high -OH group percentage. It led to poor interfacial bonding between the fibre and matrix and caused the decrement in the tensile properties (Sombatsompop and Chaochanchaikul, 2004;Diamant et al., 1981). ...
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... An increase in moisture content can affect thermal properties by creating potential cell collapses and can decrease mechanical performance by collapsing the beams, columns, or walls that bond the cells together. It has been shown that increased moisture content decreases the mechanical performance of wood-based materials (Sombatsompop and Chaochanchaikul 2004). Therefore, the lower performance values of the NCT compared to M257 and M935 can be related to lower density and higher moisture content. ...
... It affected the kenaf fibres toby having low resistivity towards moisture due to the presence of high -OH group percentage. It led to poor interfacial bonding between the fibre and matrix and caused the decrement in the tensile properties (Sombatsompop and Chaochanchaikul, 2004;Diamant et al., 1981). ...
... The increased in percentage strain at break was due to the lubrication effect by the presence of moisture, which allowed the polymer chains to slip past each other. This is because hydrogen bonding between moisture and filler was formed in the composites and the dipole-dipole interaction between PP and fillers became less effective [20]. Saleh et al. [11] also reported that the micrometre-sized dolomite particles left vacancies to be wet by the resin in the composite system if dolomite is used as single filler. ...
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In this project, the composites of polypropylene (PP)/dolomite were prepared via extrusion and injection moulding. Dolomite mineral was used as reinforcement in PP matrix. PP reinforced dolomite composites with various concentrations of dolomite (5, 10 and 15 wt%) were characterized by mechanical properties through tensile, impact and flexural test, morphological analysis by scanning electron microscope (SEM), thermal analysis by differential scanning calorimeter (DSC) and flammability analysis by the limiting oxygen index (LOI). The incorporation of dolomite into PP had improved Young's modulus while flexural modulus, tensile, flexural and impact strengths were decreased. The incorporation of dolomite up to 15 wt% increased the stiffness of the composites in tensile mode while in three point bending mode, 10 wt% dolomite was the optimum concentration. Tensile and flexural strength showed a slight reduction in the values while impact strength was continuously decreased with the addition of dolomite. SEM images showed poor interfacial adhesion between PP and dolomite, thus supported the decreased of tensile, flexural and impact strengths. The melting and crystallization temperatures (Tm and Tc) of the composites slightly increased with the addition of dolomite. LOI test showed that flammability of the composites decreased with the increasing content of dolomite.
... Composites usually conform to Fickian diffusion profiles, but this fact is verified with the experimental data of the different composite compositions. The mechanism of water diffusion into the composites was studied by analysing the slope and intercepts of the water absorption graphs plotted by using the relations in equation (2) and (3) according to Sombastsompop and Chaochanchaikul (2004). The experimental data were fitted to the logarithmic equation (3) whose slope (n) helps determines the diffusion case ...
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... The dipoledipole interaction between wood flour and polymer molecules became less effective, resulting in an increase in the flexibility of polymer chains, especially in the PA6 molecule chain. This mechanism is the molecular interaction between moisture and polyamide, with the flexibility (corresponding to an increased impact strength) of PA6 increasing with the presence of moisture 18 for the interface between the wood flour and polymer in the WPCs were identified using field emission SEM. An effective compatibilizer and toughener can improve the interfacial adhesion and consequently enhance the mechanical properties of WPCs. ...
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... Further increment in percentage of water absorption was observed at day 65 where the increase for PVC/RH40 was the highest, which is 2.4% while virgin PVC has the lowest percentage at 0.3%. This is due to the incorporation of RH, which had increased the number of microvoids caused by the larger amount of poorly bonded area between hydrophilic RH and hydrophobic PVC matrix, resulting in higher water absorption (Sombatsompop and Chaochanchaikul, 2004). This is in agreement with the proposed water absorption mechanism proposed by Lin et al. (2002), Kiani et al. (2011), and Razavi-Nouri et al. (2006), in which the water molecules are diffused through capillary action into the gaps and flaws created at the interface of polymer matrix and fiber. ...
... Water penetration can also lead to hydrolysis of epoxy resin showing that the fibre/matrix interface is degraded. In addition, Chemical-based mechanisms result in changes to the polymer matrix that are not reversible and occur primarily due to hydrolytic degradation, whereby the diffusion of water into the composite results in chain scission [5][6][7]. Goodarzi et al. [8] investigated mode II fracture and viscoelastic cohesive zone behaviour (estimation of time-dependent delamination) of viscoelastic properties of resin-rich interface of woven E-glass/epoxy composite laminate by nanoindentation technique. The mechanical properties of the composites including hardness and Young's modulus in the Cu-interface-SiC system have been investigated by Chmielewski et al. [9] via this technique. ...
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... This process is described in [40] and demonstrates that natural lignocellulosic fibres, such as flax, due to the intense presence of -OH groups, exhibit a very low resistance in the aquatic environment. In addition, the reduction in the interfacial adhesion between fibre and matrix causes dimensional variation and leads to decrease the mechanical properties these materials (as reported in [30,42,43]). ...
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... The decline of tensile properties was due to large number of hydroxyl and lumens in jute fiber, which promoted the water absorption. There was swelling of jute fiber, which can lead to the stress in composites [44]. The stress would accelerate the debonding process, resulting in the worse interface between jute fiber and PLA matrix, which also lead to the decline in tensile strength and modulus. ...
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This work focused on the durability of short jute fiber reinforced poly(lactic acid) (PLA) composites in distilled water at different temperatures (23, 37.8 and 60 °C). Morphological, thermal and mechanical properties (tensile, flexural, and impact) of jute/PLA composites were investigated before and after aging. Different from traditional synthetic fiber reinforced polymer composites, the stability of jute/PLA composites in water was significantly influenced by hydrothermal temperature. The mechanical properties of the composites and molecular weight of PLA matrix declined quickly at 60 °C, however, this process was quite slower at temperatures of 23 and 37.8 °C. Impact properties of the composites were hardly decreased, but the tensile and flexural properties suffered a drop though to various degrees with three degradation stages at 23 and 37.8 °C. The poor interface of composites and the degradation of PLA matrix were the main damage mechanism induced by hydrothermal aging. Furthermore, considering the hydrolysis of PLA matrix, the cleavage of PLA molecular chain in different aging time was quantitatively investigated for the first time to illustrate hydrolysis degree of PLA matrix at different aging time.
... Mechanical properties like tensile, flexural and hardness degrade at a higher moisture rate due to generation of hydrogen bonding across water molecules and cellulose fibre. A high percentage of hydrogen bonding is formed between cellulose macromolecules and polymers due to hydroxyl groups (-OH) present in hydrophilic natural fibres (Sombastsompop & Chaochanchaikul, 2004). ...
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Research on natural fibres has been carried out from past decades as a result of developing low cost, eco-friendly materials. The objective of this study is to fabricate composites utilising sawdust of various proportion and compare the mechanical properties like tensile, flexural and hardness within dry condition and with respect to specimens immersed in distilled and salt water. The composites with constant reinforcement 15%, different percentage of matrix (85, 80, 75, 70%) and filler (0, 5, 10, 15%), respectively by mass, are developed by hand layup method and is compared for their mechanical properties. Mechanical properties of composite fabricated from sawdust up to certain percentage showed an improvement when compared to composite with no filler; with further increase in filler, a drop in mechanical performance is noticed. An increase in tensile strength by 12.75%, flexural strength by 5.94%, hardness by 18.34%, tensile modulus by 100.3%, flexural modulus by 60.4% is observed in dry condition compared to the composite with no filler. Mechanical degradation in tensile strength, tensile modulus, hardness, flexural strength for the samples subjected to ageing in sea and distilled water is observed. Flexural modulus after ageing increased with filler addition up to a certain percentage and with further increase in filler, a decrease is noticed. Higher mechanical degradation (except flexural modulus) is observed for those specimens immersed in sea water.
... As the cost of non-renewable sources of material becomes more expensive, natural fibres can be a viable alternative as reinforcements for composite materials (Adekunle et al., 2011;. The use of natural fibres reinforced polymeric composite materials has been successfully used in a wide range of applications in recent years due to their abundant availability, lower density, and much higher specific strength than conventional fibre-reinforced composites (Dhakal et al., 2009;Jacob et al., 2004;Sombatsompop and Chaochanchaikul, 2004). The need for light weight and less CO 2 emission structures has large growth potential in demand for natural fibre reinforcements. ...
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Flax fibre-reinforced unsaturated polyester composite laminates were fabricated by vacuum bagging process and their impact and post-impact responses were investigated through experimental testing and finite element simulations. Samples of 60 mm × 60 mm × 6.2 mm were cut from the composite laminates and were subjected to a low-velocity impact loading to near perforation using hemispherical steel impactor at three different energy levels, 25, 27 and 29 Joules. Post-impact was employed to obtain full penetration. The impacted composite plates were modelled with various lay-ups using finite element software LS-DYNA (LS-DYNA User’s Manual 1997) to provide a validated finite element model for the future investigation in the field. The effects of impact and post-impact on the failure mechanisms were evaluated using scanning electron microscopy. Parameters measured were load bearing capability, energy absorption and damage modes. The results indicate that both peak load and the energy absorption were reduced significantly after the post-impact events. Consequently, it was observed from the visual images of the damages sites that the extent of damage increased with increased incident energy and post-impact events.
... Bodros et al. [8] studied that the mechanical behavior of stinging nettle fibers and compared to flax and other lignocellulosic fibers and reported that the stress/strain curve of stinging nettle fibers shown a linear behavior with a tensile modulus of 87 GPa and tensile strength as 1594 MPa. Various researchers has experimentally investigated the mechanical properties of the composites with change in fiber volume fraction [9][10][11][12] fabrication processes [13][14][15][16] chemical treatments [8,17,18] and degradation behavior [17,[19][20][21] by using sisal, hemp or nettle fiber as reinforcement and reported different results. The difference may be attributed *Corresponding author: manish.lila@gmail.com ...
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Natural fibers are lignocellulosic and hollow in nature and having good mechanical, thermal and structural properties. In the present research endeavor, three types of natural fibers (namely Sisal, Hemp and Nettle fibers) are used as reinforcement in woven mat form to fabricate 4-ply laminate composites with epoxy resin as matrix using hand layup process. Atomic force microscopy (AFM) and scanning electron microscope (SEM) have been used to get the surface roughness of fiber, to study the fracture behavior of the developed composites and effect of inter surface bonding between fibers and matrix. Thermogravimetric analysis (TGA/DTA) has been performed to study the thermal behavior and inter surface bonding among matrix and fibers for the developed composites. The results revealed that along with the applied pressure and viscosity of the matrix, surface roughness of the fiber also plays a significant role in deciding the mechanical properties and natural fiber with high surface roughness exhibits better mechanical properties.
... where m f is the mass fraction of filler in the composite and ρ C , ρ M and ρ f are densities of the composite, matrix and filler respectively [31]. The obtained densities were then used to calculate the volume percent of filler (VPF). ...
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... where m f is the mass fraction of filler in the composite and ρ C , ρ M and ρ f are densities of the composite, matrix and filler respectively [31]. The obtained densities were then used to calculate the volume percent of filler (VPF). ...
Article
Low-density polyethylene is a vastly used engineering material owing to its low cost, high formability, recyclability, relative availability and the possibility of improving its properties when reinforced/filled with other materials. However, when filled with some inorganic particulates, increase in the population of the particulates leads to increased hydrophilicity in the material and a weakened mechanical bonding energy between the fillers and the matrix material overtime. This study has demonstrated that optimum combination of mechanical and hydrophilic properties of low-density polyethylene for water-based applications can be achieved by filling its matrix with 1 – 3 volume % of 0.5 µm particulates of TiO2. The composites used in this study were developed by compression moulding technique and studied via scanning electron microscopy, tensile, flexural and water absorption tests.
... This is not desirable considering polymer composites applications in which mentioned fibers are employed in the role of the filler. Elevated water content in cellulose powder may contribute to, e.g., poor polymer composite mechanical properties [14], weak fillermatrix adhesion [15], or depressed decomposition temperature of a product [16]. ...
Article
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The following article highlights the importance of an indispensable process in cellulose fibers (UFC100) modification which may change the biopolymer properties—drying. The reader is provided with a broad range of information considering the drying process consequences on the chemical treatment of the cellulose. This research underlines the importance of UFC100 moisture content reduction considering polymer composites application with the employment of a technique different than thermal treating. Therefore, a new hybrid chemical modification approach is introduced. It consists of two steps: solvent exchange (with ethanol either hexane) and chemical treatment (maleic anhydride—MA). With the use of Fourier-transform infrared spectroscopy (FT-IR), it has been proven that the employment of different solvents may contribute to the higher yield of the modification process as they cause rearrangements in hydrogen bonds structure, swell the biopolymer and, therefore, affect its molecular packing. Furthermore, according to the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the improvement in fibers thermal resistance was noticed, e.g., shift in the value of 5% temperature mass loss from 240 °C (regular modification) to 306 °C (while solvent employed). Moreover, the research was broadened with cellulose moisture content influence on the modification process—tested fibers were either dried (D) or not dried (ND) before the hybrid chemical treatment. According to the gathered data, D cellulose exhibits elevated thermal resistance and ND fibers are more prone to the MA modification. What should be emphasized, in the case of all carried out UFC100 treatments, is that a decrease in moisture contend was evidenced—from approximately 4% in case of thermal drying to 1.7% for hybrid chemical modification. This is incredibly promising considering the possibility of the treated fibers application in polymer matrix.
... fiber content on the mechanical properties was studied [15]. In another study, slit extrudates were manufactured from poly(vinyl chloride) and wood sawdust by using a twin-screw extruder to study the effect of sawdust moisture content on the mechanical properties of the produced composite [16]. Pan et al. experimented with starch and PLA blends to prepare injection molded composite specimens and studied the effect of moisture content on the tensile properties [17]. ...
Thesis
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Moisture absorption into hygroscopic/hydrophilic materials used in fused deposition modeling (FDM) and ultrasonic welding (USW) can diminish desired mechanical properties. Sensitivity to moisture is dependent on material properties and environmental factors and needs characterization. In this thesis, moisture sensitivity of PLA filaments and PLA/PBS blended filaments was characterized in FDM printed ASTM test samples post-conditioning the filaments at different relative humidity levels. Tensile strength decreased with increase in moisture content. Parts made with PLA 4043D, PLA/PBS 75/25 filaments were most sensitive to moisture. Investigation of tensile properties of parts made with PLA filaments exposed to room temperature and humidity conditions for three months showed a more significant decrease. Moisture sensitivity of PLA, PBS, and PLA/PBS 25/75 blend characterized for USW using injection-molded industrial standard test parts (ISTeP) showed a downward trend in weld strength for 100% PLA and PLA/PBS 25/75 while 100% PBS was significantly affected at high moisture conditions.
... Further, the thermal stability of the composites shifted to even lower temperature, compared to that of the composites subjected to accelerated weathering. As reported by Sombatsompop and Chaochanchaikul [55], higher moisture content decreases the thermal stability of composites. This may be explained by the fact that moisture absorption causes fiber swelling, which leads to the microcracking mechanism in the matrix around swollen fibers. ...
Article
This study aims to gain insight into the influence of environmental effects on the colour, biodegradability, oxidation stability, thermal stability and complex modulus of bamboo/kenaf fiber reinforced epoxy hybrid composites. The composites were prepared by the hand lay-up technique, with a fixed loading of 40% fibers for all the composites. Three types of hybrid composites were prepared with different mixing ratios of bamboo fibers (B) to kenaf fibers (K): (i) 30:70, (ii) 50:50, and (iii) 70:30. Kenaf/epoxy and bamboo/epoxy composites, as well as pure epoxy, were also prepared for comparison purposes. The kenaf, bamboo and hybrid composites were exposed to UV radiation at elevated temperature and humidity, for a total exposure period of 156 h. The colour changes occurring during the weathering process were assessed by colorimetric analysis. The effects of soil burial on the developed composites were also studied for different time periods of 3, 6 and 12 months. Thermal properties, in terms of oxidation stability, thermal stability and dynamic mechanical properties, were determined by differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis, respectively. The results obtained from colorimetric analysis indicated that increasing the bamboo fiber loading in the formulation of hybrid composites induced higher total colour changes. The biodegradability of hybrid composites at higher kenaf loading increased as the soil burial period was longer. Overall, soil burial has led to more pronounced degradation, as compared to accelerated weathering, in terms of oxidation stability, thermal stability and dynamic mechanical properties. The findings of this work reveal that the hybrid composite formulation B:K:50:50 presents a balance of resistance to environmental effects, while maintaining the biodegradability characteristic, which makes it suitable for its use as a potential biocomposite material for structural applications.
... During the second stage, the water molecules actively attacked the PLA, which caused debonding between the jute fibers and PLA matrix, thus giving rise to cracks in the PLA matrix. In addition, there was swelling of jute fiber and PLA matrix, which can lead to the internal stress in composites [44]. The stress would accelerate the debonding process, resulting in the worse interface between jute fiber and PLA matrix. ...
Article
This paper investigates the effect of short jute fibers on the hydrolysis of poly (lactic acid) (PLA) in deionized water at 50 and 60 °C. The water absorption, thermal and mechanical properties (tensile and flexural), morphological structure, as well as molecular weight of jute/PLA composites and PLA were evaluated before and after aging. The results showed that the jute/PLA composites had higher water absorption but approximately equal mechanical properties compared with PLA. This indicates that it is a feasible way to reinforce PLA by adding short jute fibers. Both PLA and jute/PLA composites undergo hydrolysis after aging. Further analysis revealed that as the vibration and mobility of PLA molecular chains were hindered by addition of jute fibers, jute/PLA composites had a slower decline in mechanical properties than PLA, and thus showed a slower hydrolysis. Moreover, the addition of jute fibers resulted in mechanical interlocking, which in turn increased the load carrying capability of jute/PLA composites.
... This process is temperature-dependent and more distinct in temperatures above those of the human body. However, this has been described from temperatures of 23 • C upwards [31,32]. This moisture content has a relevant influence on the mechanical heaviness of PP. ...
Article
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The introduction of alloplastic materials (meshes) in hernia surgery has improved patient outcome by a radical reduction of hernia recurrence rate, but discussion about the biocompatibility of these implanted materials continues since observations of surface alterations of polypropylene and other alloplastic materials were published. This study intends to investigate if additives supplemented to alloplastic mesh materials merge into the solution and become analyzable. Four polypropylene and one polyester alloplastic material were incubated in different media for three weeks: distilled water, saline solution, urea solution, formalin, and hydrogen peroxide. No swelling or other changes were observed. Infrared spectroscopy scanning of incubated alloplastic materials and NMR studies of extracted solutions were performed to investigate loss of plasticizers. The surface of the mesh materials did not show any alterations independent of the incubation medium. FT-IR spectra before and after incubation did not show any differences. NMR spectra showed leaching of different plasticizers (PEG, sterically hindered phenols, thioester), of which there was more for polypropylene less for polyester. This could be the reason for the loss of elasticity of the alloplastic materials with consecutive physically induced surface alterations. A mixture of chemical reactions (oxidative stress with additive leaching from polymer fiber) in connection with physical alterations (increased elasticity modulus by loss of plasticizers) seem to be a source of these PP and PE alterations.
... And also, occurring micro cracks can be avoided by proper curing of the material as explained by Kalpakjian & Schmid, (2010). Furthermore, various surface modifications, such as the use of coupling agents, alkali treatment, latex coating, mercerization and irradiation of wood fiber have been applied in order to reduce hydrophobicity and to improve compatibility between the wood and the polymer (Sombatsompop & Chaochanchaikul, 2004). The effect of coupling agents on enhancing the properties of wood-plastic composites has been the subject of many publications (Bledzki, et al., 2005). ...
Thesis
This study was aimed at developing a method to invent and produce wood-plastic composite light construction material from post-consumer plastic wastes. The method was to blend shredded Polypropylene (PP) plastic films with wood sawdust into a hot mixture, which could be moulded to form required shapes. A laboratory level small extruder with Infrared heating elements was used to prepare the blend and standard drop hammer was used to compact the mixture in cylindrical moulds. Different ratios of plastic and wood sawdust were blended and tested for mechanical properties and physical properties of wood-plastic composites. Under the mechanical properties, compressive strength and splitting tensile strength were tested and density, water absorption, thickness swelling and linear expansion were tested under the physical properties. The compressive strength test results showed that the average compressive strength ranged between 6.656 MPa to 14.038 MPa in different wood-plastic composites while the average values of splitting tensile strength ranged between 0.559 MPa to 1.544 MPa. Plastic-sawdust ratio of 80%-20% (wt %) blended at 180˚C resulted in maximum average compressive strength of 14.038 MPa and relatively higher average splitting tensile strength of 1.344 MPa than other ratios. Also, water absorption, thickness swelling and linear expansion results showed that the plastic-sawdust ratio of 50%-50% (wt %) has the highest average values while the plastic-sawdust ratio of 80%-20% (wt %) and 90%-10% (wt %) have the lowest values. According to the results, it can be concluded that the best mixture for producing light construction material is the plastic-sawdust ratio of 80%-20% (wt %).
... The moisture in the composites may interfere with the absorption effects by decreasing the effects of physical bonding and potentially acting as a lubricant between the polymer phases. A study by Sombatsompop and Sims (2004) suggested that to optimize the mechanical properties of polymers, the moisture content in the compound should be less than 1% [33]. ...
Article
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Medical imaging phantoms are considered critical in mimicking the properties of human tissue for calibration, training, surgical planning, and simulation purposes. Hence, the stability and accuracy of the imaging phantom play a significant role in diagnostic imaging. This study aimed to evaluate the influence of hydrogen silicone (HS) and water (H2O) on the compression strength, radiation attenuation properties, and computed tomography (CT) number of the blended Polydimethylsiloxane (PDMS) samples, and to verify the best material to simulate kidney tissue. Four samples with different compositions were studied, including samples S1, S2, S3, and S4, which consisted of PDMS 100%, HS/PDMS 20:80, H2O/PDMS 20:80, and HS/H2O/PDMS 20:40:40, respectively. The stability of the samples was assessed using compression testing, and the attenuation properties of sample S2 were evaluated. The effective atomic number of S2 showed a similar pattern to the human kidney tissue at 1.50 × 10−1 to 1 MeV. With the use of a 120 kVp X-ray beam, the CT number quantified for S2, as well measured 40 HU, and had the highest contrast-to-noise ratio (CNR) value. Therefore, the S2 sample formulation exhibited the potential to mimic the human kidney, as it has a similar dynamic and is higher in terms of stability as a medical phantom.
... The value of "n" is an indication of the mechanism of sorption (George, Thomas, and Thomas 1999;Katoch, Sharma, and Kundu 2010). The diffusion (D) and sorption (S) coefficients were calculated from Equations (4) and (5), respectively (Crank 1979;Sombatsompop and Chaochanchaikul 2004;Thwe and Liao 2002). ...
Article
The sustainable utilisation of Kenaf fibres (KF) as environmentally friendly reinforcement in mortar, concrete and polymer composites promotes the concept of a circular economy and sustainable construction. However, the hydro-philic nature of such biofibres adversely affects their structural applications as reinforcement in concrete, mortar and polymer. Therefore, the study examined the effect of alkali treatment (mercerization) on the surface sorption characteristics of KF. The effect of water sorption characteristics on the mechanical properties of surface-modified and untreated KF was also investigated in the study. Scanning electron microscopy was performed to examine the morphology and microstructure of the fibre surface along with the tensile fracture of the swollen/ un-swollen fibres. The water absorption studies revealed that mercerization reduced the overall water uptake of KF by 16%, which enhanced the adhesion of the fibre surface. The findings provide the knowledge required by scientists and engineers for determining the water requirements for the design of bio-fibrous concrete composites.
... 30%) are not so crucial because they do not have a significant impact on the final properties. Moisture content fluctuation changes the mechanical properties of wood-based composite panels (Halligan and Schniewind 1974;Wu and Suchsland 1997;Lin et al. 2002;Sombatsompop and Chaochanchaikul 2004;Janssen 2018). ...
Article
Wood quality depends on many circumstances, as it is sensitive to changing properties, depending on the environment. This work evaluates the influence of moisture content of selected wood-based composites on their basic mechanical properties, i.e., modulus of rupture and modulus of elasticity. The selected panels were divided by application in construction materials and furniture materials, which demand specific conditions during service-life. The increase of moisture content in different types of wood-based panels resulted in a slight reduction of the modulus of rupture and the modulus of elasticity. Boards for use in dry conditions, mainly in the furniture industry, were more sensitive to lowering their modulus of elasticity with higher board moisture content compared with those designed for humid conditions, mainly from the building industry.
... The good damping properties of bast fibrereinforced composites make them an attractive alternative to be used in automotive components where impact and damping properties are very important [11,12]. However, their high natural variability, strong affinity to water until saturation, limited processing temperature range, relatively low impact resistance, and low thermal stability negatively influence their long-term durability [13,14]. Moreover, their low impact resistance behaviour under different operation conditions is another concern when these materials are used in automotive and marine sectors. ...
Article
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Understanding the damage mechanisms of composite materials requires detailed mapping of the failure behaviour using reliable techniques. This research focuses on an evaluation of the low-velocity falling weight impact damage behaviour of flax-basalt/vinyl ester (VE) hybrid composites. Incident impact energies under three different energy levels (50, 60, and 70 Joules) were employed to cause complete perforation in order to characterise different impact damage parameters, such as energy absorption characteristics, and damage modes and mechanisms. In addition, the water absorption behaviour of flax and flax basalt hybrid composites and its effects on the impact damage performance were also investigated. All the samples subjected to different incident energies were characterised using non-destructive techniques, such as scanning electron microscopy (SEM) and X-ray computed micro-tomography (πCT), to assess the damage mechanisms of studied flax/VE and flax/basalt/VE hybrid composites. The experimental results showed that the basalt hybrid system had a high impact energy and peak load compared to the flax/VE composite without hybridisation, indicating that a hybrid approach is a promising strategy for enhancing the toughness properties of natural fibre composites. The πCT and SEM images revealed that the failure modes observed for flax and flax basalt hybrid composites were a combination of matrix cracking, delamination, fibre breakage, and fibre pull out.
... The decrease in flexural strength with higher water absorption content may be related to the formation of hydrogen bonding between the water molecules and FPFs. FPFs with high hydroxyl groups (−OH) percentage in the fiber structure will form a large number of hydrogen bonds between the macromolecules of the fibers cellulosepolymer and results in low water resistance [43]. This leads to low dimension stability of composites products and poor interfacial adhesion between the fibers-matrix. ...
Article
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This study aims to investigate the effect of silane, alkali, and a combination of alkali–silane treatments on the water absorption behavior, mechanical and thermal properties of woven fan palm fibers (WFP)-reinforced unsaturated polyester composites. Maximum moisture content (Mm) and diffusivity (D) values of treated WFP composites immersed in 3.5% NaCl solution both at room temperature and 60 °C were found to be lower than those of untreated WFP composite. The water absorption patterns of the composites immersed at room temperature were found to follow Fickian behavior, contrary to those immersed at 60 °C. The chemical treatments enhanced significantly the tensile and flexural strength of WFP composites. The water absorption reduced drastically the tensile, flexural, and impact strength of WFP composites. The tensile, flexural and impact strength of the treated composites immersed at 60 °C was lower than at room temperature. The thermal stability of alkali-treated WFP composite was slight higher than that for the untreated and silane-treated WFP composites.
... These groups form a large number of hydrogen bonds between the macromolecules of the cellulose and polymer. The presence of a large number of -OH group leads to a low moisture resistance, hence leading to a poor interfacial bonding between fibre and the matrix [23]. ...
Article
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Due to rigorous new environmental legislations, automotive, marine, aerospace, and construction sectors have redirected their focus into using more recyclable, sustainable, and environmentally friendly lightweight materials driven by strengthening resource efficiency drive. In this study, the influence of moisture absorption on flax and flax/glass hybrid laminates is presented with the aim to investigating their low velocity impact behaviour. Three different types of composite laminates namely, flax fibre reinforced vinyl ester, flax fibre hybridised glass fibre and glass fibre reinforced vinyl ester composites were fabricated using resin infusion technique. The moisture immersion tests were undertaken by immersing the different specimens in sea water bath at room temperature and 70 °C at different time durations. The low velocity falling weight impact testing was performed at 25 Joules of incident energy level and impact damage behaviour was evaluated at both ageing conditions using scanning electron microscopy (SEM) and X-ray microcomputed tomography (micro CT). The percentage of moisture uptake was decreased for flax vinyl ester specimens with glass fibre hybridisation. The maximum percentage of weight gain for flax fibre, flax/glass hybrid and glass fibre reinforced composites immersed at room temperature for 696 h is recorded at 3.97%, 1.93%, and 0.431%, respectively. The hybrid composite exhibited higher load and energy when compared flax/vinyl ester composite without hybridisation, indicating the hybrid system as a valid strategy towards achieving improved structural performance of natural fibre composites. The moisture absorption behaviour of these composites at room was observed to follow Fickian behaviour.
... MPa, respectively) and the flexural moduli of the composites (3 MPa to 80 MPa and 1 MPa to 72 MPa, respectively) [31]. Both cold and hot pressing were associated with significant reductions in the strain to failure of the samples, resulting from the reduced moisture content of the composites following pressing, which would otherwise act as a plasticiser [97]. Cold pressing of P. ostreatus grown on rapeseed straw reduced their strain to failure (2.8% to 0.8%), while hot pressing of P. ostreatus and T. multicolor grown on rapeseed straw was associated with lower strain to failure (2.8% to 0.7% and 4.7% to 0.9%, respectively) [31]. ...
Article
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Mycelium composites are an emerging class of cheap and environmentally sustainable materials experiencing increasing research interest and commercialisation in Europe and the United States for construction applications. These materials utilise natural fungal growth as a low energy bio-fabrication method to upcycle abundant agricultural by-products and wastes into more sustainable alternatives to energy intensive synthetic construction materials. Mycelium composites have customisable material properties based on their composition and manufacturing process and can replace foams, timber and plastics for applications, such as insulation, door cores, panelling, flooring, cabinetry and other furnishings. Due to their low thermal conductivity, high acoustic absorption and fire safety properties outperforming traditional construction materials, such as synthetic foams and engineered woods, they show particular promise as thermal and acoustic insulation foams. However, limitations stemming from their typically foam-like mechanical properties, high water absorption and many gaps in material property documentation necessitate the use of mycelium composites as non- or semi-structural supplements to traditional construction materials for specific, suitable applications, including insulation, panelling and furnishings. Nonetheless, useful material properties in addition to the low costs, simplicity of manufacture and environmental sustainability of these materials suggest that they will play a significant role in the future of green construction.
... Literature review reveals that work has been done on glass fibre reinforced epoxy composite, wood polymer composites and sawdust as filler in polypropylene, but very little work was carried out sawdust as secondary fibre with glass fibre reinforced epoxy [9][10][11]. Composite materials are classically used for the construction of buildings, bridges, and some of the structures like boat hulls, natatorium panels, motorcar bodies, shower stalls, bathtubs, storage tanks, cultivated marble sinks and countertops. ...
Chapter
The need for bio-based composites or biocomposites has been increasing over recent years as a measure for sustainable development and to minimize the use of petrochemical-based plastics to reduce global warming. However, the properties of biocomposites are hugely influenced by the environmental parameters because of their inherent material properties. Therefore, in this chapter, the coupled effect of temperature and moisture on the overall mechanical properties of biocomposites is discussed under the framework of hygrothermal ageing. The variation in the parameters of hygrothermal ageing such as the relative humidity, temperature, and ageing time have different effects based on the type of composite, its composition, and the properties of the constituent materials of the composites. These variables may either enhance or deteriorate the properties of such composites. This chapter aims to provide a consolidated understanding of the effects of these variables on the mechanical properties of the biocomposites such as the tensile strength, compressive strength and modulus, flexural rigidity, impact toughness, dynamical mechanical properties such as the storage modulus, loss modulus and the damping coefficient, fatigue properties, shear properties, and many others. The sections in this chapter are designed to discuss the effects of hygrothermal parameters on the said properties exclusively. Additionally, care has been exercised to include biocomposites used in a wide variety of applications including those used in tissue engineering, aerospace components, automobile components, structural components, and many others.
Article
In this research, the load bearing behavior of strengthened hollow WPVC composite log-wall panels using steel flat bars (SFBs) was examined experimentally and verified numerically with a finite element model (FE-model). The validated FE-model was extended to study the load carrying behavior of full-scale log-wall panels. The results indicated that the new log element cross-section gave an average maximum load-bearing capacity of 40.3 kN/m at an average maximum displacement of 12.07 mm and prevented side sway and fracture near the connection between the web and the flange. For the strengthened middle part between the openings of the log-wall panel, SFBs and an extra flange member provided an average maximum load-bearing capacity of 48 kN/m at an average maximum displacement of 20.4 mm, and helped to control the deformation shape, prevented the separation of log layers, and provided the panel with low ductility. Good bonding between the contact surfaces of the WPVC composite and the SFBs was achieved. In a comparison between the experiment and the FE-model simulation, similar trends in the load–displacement relationship, strain intensity, and deformed shape were obtained, which confirmed the accuracy of the FE-model used. The numerical results for full-scale log-wall panels using the validated FE-model also showed that WPVC composite panels with two openings can carry loads of 4.12 and 4.69 kN/m, which satisfies the requirements for a load-bearing wall in a one-story house with a roof span of up to 4 m and a total load of less than 3.28 kN/m, excluding the lateral load.
Patent
A composite comprises a thermoplastic elastomer and a plant flour. This composite has an increased thermal stability and can be used in a construction material. The invention also provides a method for producing the composite, said method comprising the steps of introducing a thermoplastic elastomer and a plant flour into an extruder and extruding the resulting mixt.
Article
Sawdust or wood shaving is a relatively abundant and inexpensive lignocellulosic compound, which is provided by mother nature. It is a waste of industry and agriculture, that is found in large quantities and has disposal problems. Nowadays, waste management (like sawdust) and research on converting it to different compounds for special applications and goals have been receiving tremendous attention. So, introducing sawdust as a kind of interesting bio-waste and turn it into wealth for diverse utilizations can be mentioned as the main goal of this overview. In this regard, in the first part, sawdust structure and properties are considered. It is then followed by highlighting its wide applications in sustainable water remediation technology, production of activated carbon, oil-water separation, and high-performance composites fabrication. Please come on to start a journey on this motivating topic.
Chapter
Nowadays concerns over global warming favored research to focus on the environmental pollution and waste accumulation and on the possibility to recycle and up-cycle the waste. A particular class of such waste consists of natural remains and by-products from agriculture and industries, such as forestry, pulp and paper, furniture, and food industry. There are various methods to upcycle and capitalize the agro-industrial waste: (1) anaerobic digestion for energy production; (2) thermal conversion for the resulting liquids and char that may be further used in obtaining other materials, bioplastics included; (3) industrial processing to obtain natural fibers, long or short, able to be employed as reinforcing materials in biocomposites (multicomponent systems where the matrix consists of polymers or polymer blends, either synthetic or natural; they may also contain emulsifiers, compatibilization agents, antioxidants, as well as inorganic, organic, metal, or metal oxides micro- and/or nanoparticles); and (4) composting. Composites based on agro-industrial waste displayed a level of performance high enough to grant their use in a wide variety of applications: furniture and civil constructions; interior design, fencing, and decking; automotive and aerospace industry; food and general packaging. To obtain such materials, it is necessary to consider specific issues, the most important being the compatibility between matrices and reinforcing material. Characteristics of the final material (mechanical, thermal, water sorption, weather resistance) strongly depend on a good compatibility. A critical assessment of the selected methodology is necessary as it is reflected in the final cost of production, which must be limited in relation to the envisaged application.
Article
The fire-retardant and water-repellent bio-structural panels (BISPs) were successfully developed using cellulose nanofibrils, corn starch, boric acid, and n-dodecenyl succinic anhydride with adhesive-free character. Its performance properties were evaluated and compared with other well-known products on the market. The BISP's density (0.1 g/cm³) and permeance value [41.81 g/day/m² with 5.76% coefficient of variation (CV)] were found higher than compared competitor products. The BISPs' contact angle was found 132.13° (1.59% CV) for BISP. The BISP was the only fire-retardant product, and the only one developed almost no smoke 2.20%.
Article
The present study aims to investigate the water absorption property and its effect on the mechanical properties (i.e. tensile, flexural, and impact) of bionanocomposites. The epoxy-based bionanocomposites were prepared by reinforcing the epoxy with 1, 2, 3, 4, and 5 wt% of nanocellulose using in situ polymerization method. The maximum water uptake by bionanocomposites was measured; however, the water absorption behavior was not found in accordance with Fickian’s diffusion model. In the present study, very low water absorption in the range of 0.17–0.34% was offered by bionanocomposites. The results obtained from the present experimental study suggested that there were a maximum degradation of 14.96% in tensile strength, 26.44% in flexural strength, and 55.66% in impact strength for bionanocomposites reinforced with 5 wt% of nanocellulose by water uptake.
Article
Purpose The purpose of this study is to manufacture composites from sawdust and polymer high-density polyethylene (HDPE) with different loading from alum as natural and cheap flame retardant and subsequently characterized using standard analytical tools. Design/methodology/approach Artificial wood plastic composites (WPCs) were prepared by mixing HDPE with sawdust as a filler with constant ratio (2:1) using hot press. Polyethylene-graft-maleic anhydride (PE-g-MAH) used as a coupling agent between two parents of the composites with different ratios (2.5, 5, 7 and 10). Alum as a flame retardant was incorporated into HDPE with 5 phr polyethylene grafted with maleic anhydride (PE-g-MAH) with different ratios (10, 15 and 20). Flame retardant efficiency was investigated using differential scanning calorimetry, thermal gravimetric analysis and the technique of ASTM E162. Findings The results revealed that the composite containing 5 phr from (PE-g-MAH) exhibited higher mechanical properties and this proved that (PE-g-MAH) act as an efficient coupling agent using the aforementioned ratio. The results also revealed that incorporation of alum as a flame retardant increased the thermal stability of the composites. Originality/value Artificial WPCs are ecofriendly materials with a wide range of applications in the constructions field. Moreover, they have high mechanical and physical properties with low cost. Evaluate alum as a natural and cheap flame retardant.
Article
Good dispersion of the nanoparticles into the polymer is considered a critical issue, as it can provide higher strength and stiffness while poor dispersion is seen to decrease those properties. In the present work, the effect of three ultrasonic parameters (amplitude, time and cycle of sonication) on sonication technique for dispersing 1 wt.% nano-clay in polyester matrix was investigated. To disperse the nano-clay into the polyester matrix, sonication frequencies of 40% and 80%, sonication times of 0.5, 1 and 2 hours and pulse of 0.5 and 1 cycle were used. The effect of these ultrasonication parameters on water barrier and impact behavior of unfilled and filled glass fiber (GF)/polyester with nano-clay under dry, distilled and seawater conditions was studied. Results showed that, water absorption of nano-filled composites dispersed with all sonication parameters is lower than that of unfilled glass fiber/polyester composites immersed in distilled and seawater. Nano-clay filled GF/polyester composites showed an improvement in impact resistance under dry, distilled and seawater conditions with all sonication parameters. Among the used sonication parameters; time of 2 hours, amplitude of 40% and 0.5 cycle was found as the best parameter which resulted in the maximum enhancement in impact resistance, due to the addition of nano-clay to GF/polyester, of 8.2%, 14% and 19.6% under dry, distilled water and seawater conditions, respectively. Nonlinear minimization approach was exploited using MAPLE commercial software in order to find the suitable fit to the models of Fick and Langmuir. Diffusion coefficients for different sonication times were computed.
Article
This work aimed to examine flame retardancy, antifungal performance and physical–mechanical properties for silane-treated wood–polymer composites (WPCs) containing zinc borate (ZnB). ZnB with content from 0.0 to 7.0 wt% was added to WPCs, and silane-treated wood contents were varied. The polymers used were poly(vinyl chloride) (PVC) and high-density polyethylene (HDPE). The decay test was performed according to the European standard EN 113. Loweporus sp., a white-rot fungus, was used for antifungal performance evaluation. Antifungal performance was observed to decrease with wood content. Incorporation of ZnB at 1.0 wt% significantly increased the antifungal performance of WPCs. ZnB content of greater than 1.0 wt% lowered the antifungal properties of WPCs. The results suggested that the wood/PVC composite exhibited better antifungal performance than the wood/HDPE composite. The addition of wood flour to PVC and HDPE decreased flame retardancy, whereas the incorporation of ZnB retained the flame retardancy. ZnB was found to be more appropriate for wood/PVC than wood/HDPE as a result of hydrogen chloride generated from the dehydrochlorination reaction of PVC. The results indicated that the addition of ZnB did not affect the physical-mechanical properties of neat polymers and the composites. Copyright
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The resistance of bamboo fiber reinforced polypropylene composite (BFRP) and bamboo-glass fiber reinforced polypropylene hybrid composite (BGRP) to hygrothermal aging and their fatigue behavior under cyclic tensile load were studied. Injection molded samples were exposed in water at 25 °C for up to 6 months and at 75 °C for up to 3 months. Tensile strength and elastic modulus of BFRP and BGRP samples have shown moderate reduction after aging at 25°C after 6 months, however, they were reduced considerably after aging at 75°C for 3 months. Moisture absorption and tensile strength degradation are suppressed by using maleic anhydride polypropylene (MAPP) as a coupling agent in both types of composite systems. BFRP and BGRP samples were also loaded cyclically at maximum cyclic load of 35, 50, 65, and 80% of their ultimate tensile stress. Results suggest that BGRP has better fatigue resistance than BFRP at all load levels tested.
Article
The effect of interphase microstructure on the bulk mechanical properties and moisture absorption of Nylon 66 reinforced with E-glass or high-modulus (AS4) carbon fibers was examined. These particular composite systems were chosen because of their propensity to form distinct transcrystalline interphases. A comparison of mechanical properties was made by dynamic mechanical analysis (DMA) and Minimat off-axis tensile testing of samples with and without this unique interphase. Moreover, a newly developed vibrational testing technique was used and correlated with DMA to ascertain changes in the damping characteristics of the composites. The major contribution of this work is the systematic translation of single-filament (microscopic) results to bulk composite mechanical property results in the same well-characterized system. This was accomplished by studying both glass- and carbon-fiber/Nylon 66 composites. The E-glass- and carbon-fiber-reinforced Nylon 66 composites have better ultimate properties when the transcrystalline interphase is absent, but the composites have better damping properties when transcrystallinity is present. Finally, upon moisture exposure, suppression of the glass transition temperature was evident, as the water served as a plasticizer in all composites. The presence of transcrystallinity did not alter the adsorption kinetics of the composites.
Article
The effect of interphase microstructure on the bulk mechanical properties and moisture absorption of Nylon 66 reinforced with E-glass or high-modulus (AS4) carbon fibers was examined. These particular composite systems were chosen because of their propensity to form distinct transcrystalline interphases. A comparison of mechanical properties was made by dynamic mechanical analysis (DMA) and Minimat off-axis tensile testing of samples with and without this unique interphase. Moreover, a newly developed vibrational testing technique was used and correlated with DMA to ascertain changes in the damping characteristics of the composites. The major contribution of this work is the systematic translation of single-filament (microscopic) results to bulk composite mechanical property results in the same well-characterized system. This was accomplished by studying both glass- and carbon-fiber/Nylon 66 composites. The E-glass- and carbon-fiber-reinforced Nylon 66 composites have better ultimate properties when the transcrystalline interphase is absent, but the composites have better damping properties when transcrystallinity is present. Finally, upon moisture exposure, suppression of the glass transition temperature was evident, as the water served as a plasticizer in all composites. The presence of transcrystallinity did not alter the adsorption kinetics of the composites.
Article
It is believed that the moisture that is inherently present in nondried wood-fibers adversely affects the cell morphology of plastic/wood-fiber composite foams processed in extrusion. Based on this hypothesis, achieving a continuous extrusion-based production of fine-celled plastic/wood-fiber composite foams witha desirable quality would be strongly conditioned by the efficiency of the system designed for uninterrupted wood-fiber moisture elimination. This paper presents an innovative approachin addressing this problem by implementing the well-known cascade devolatilizing system in a chemical blowing agent (CBA) based production of plastic/wood-fiber composite foams. It comprises a moisture-evaporation tandem extrusion system equipped witha vent at the interconnection of the two extruders to serve for purging the moisture in the atmosphere. In order to check the performance of the newly developed system, an experimental study has been carried out for comparing the cell morphology and the volume expansion ratios of the foams obtained by processing identically formulated foamable plastic/wood-fiber composite mixtures using simultaneously the cascade devolatilizing tandem extrusion system and a corresponding single extruder withno vent. The experimental results revealed that the foams produced by using the cascade devolatilizing tandem system exhibited significantly improved cell morphologies and surface quality.
Article
Jute fiber-reinforced polypropylene composites have been produced and characterized in order to investigate the influence of water on their mechanical properties. Being hydrophilic, jute fibers absorb a high amount of water causing swelling of fibers. On the other hand, the thermal shrinkage of polypropylene melt leaves some gaps between jute fibers and matrix material. We investigated whether these gaps could be filled by the swelling of wetted fibers. The fillup of these gaps would result in a higher shear strength between fibers and matrix during fracture. Our results suggest that swelling of jute fibers in a composite material can have positive effects on mechanical properties. © 1994 John Wiley & Sons, Inc.
Article
The effect of varying the die entrance angle and the die length on extrudate swell and on the onset of extrudate distortion in capillary extrusion has been studied. Using theory from the literature, we have analyzed the contribution to the total pressure drop from the elongational and shear deformation in the entrance region, and from the capillary pressure drop in the land region of the die. From the contribution of the elongational deformation, we obtained an estimate for the elongational viscosity of the polymer. The same analysis was used to study the influence of the die geometry on the stick-slip instability. It is found that the elongational component at the inlet region mainly influences the extrudate distortions. The onset of the stick-slip instability occurs within 10% at a wall stress τw of 0.3MPa, where τw is calculated from expressions assuming fully developed flow. The variation around this average value is systematic with changes in die geometry, and the observed variations are probably due to the non-homogeneous pressure field in the die. We also propose a model for predicting extrudate swell. Input to the model are material parameters obtainable from oscillatoric measurements of the loss and storage modulus and residence times calculated from the geometry of the die. The swell model includes a fitting parameter that sets the overall scale of the swell.
Article
The development of composites consisting of wood fibers and recycled plastics offers not only an opportunity to utilize an abundant natural resource but also a means to alleviate the serious plastics disposal problem. In this work, aspen fibers are incorporated into recycled high density polyethylene with a co-rotating inter-meshing twin-screw extruder to study processing-property relationships. Tensile, impact, and flexural strengths are measured as functions of fiber concentration. The effects of fiber pretreatment, screw configuration, and compounding temperature on the properties of composites are discussed.
Article
This paper presents an experimental study on foam processing of polystyrene (PS) and high-impact polystyrene HIPS/wood-fiber composites in extrusion using moisture as a blowing agent. Wood-fiber inherently contains moisture that can potentially be used as a blowing agent. Undried wood-fiber was processed together with PS and HIPS materials in extrusion and wood-fiber composite foams were produced. The cellular morphology and volume expansion ratios of the foamed composites were characterized. Because of the high stiffness of styrenic materials, moisture condensation during cooling after expansion at high temperature did not cause much contraction of the foamed composite and a high volume expansion ratio up to 20 was successfully obtained. The experimental results showed that the expansion ratio could be controlled by varying the processing temperature and the moisture content in the wood fiber. The effects of a small amount of a chemical blowing agent and mineral oil on the cell morphologies of plastic/wood-fiber composite foams were also investigated.
Article
The capillary die flow of high density and linear low density polyethylenes is simulated under slip conditions to investigate the origin of sharkskin melt fracture. As suggested in the literature, it is shown that sharkskin originates at the exit of the die and is due to the acceleration (high stretching rate) of the melt as it exits the die. It is also shown that both adhesion and slip promoters eliminate surface defects by decreasing the stretching rate of the polymer melt at the exit region of the die. The effect of length-to-diameter ratio of the die on the sharkskin melt fracture is also examined. It is found that sharkskin is more pronounced in short dies which is in accord with experimental observations. Finally, it is suggested that applied pressure at the capillary exit suppresses surface defects.
Article
This paper investigates the structural changes of polyvinyl chloride (PVC) in melt-blends of a low-density polyethylene (LDPE) and polyvinyl chloride (PVC), and the effects of LDPE content and number of extrusion passes. These effects were examined in terms of changes in weight average molecular weight and number average molecular weight, polyene and carbonyl indices, color changes of the blend, and the variations in glass transition and decomposition temperatures. It was found that loading LDPE into PVC led to the formation of short-chain LDPE grafted PVC (s-LDPE-g-PVC) copolymers, via a macro-radical cross-recombination reaction, which had greater weight average molecular weight with unchanged number average molecular weight, increased decomposition temperature, lower glass transition temperature, as compared to the pure PVC sample. The dehydrochlorination reaction of PVC was suppressed by the macro-radical cross-recombination reaction with addition of LDPE, the effect being more pronounced at 13.0 wt% LDPE. For a given LDPE content, the macro-radical cross-recombination and dehydrochlorination reactions competed with one another, thus causing the increases in molecular weight average and molecular weight number up to the 4th extrusion pass. At the 5th extrusion pass, the dehydrochlorination reaction was predominant owing to a depletion of LDPE content to be grafted onto PVC molecular chains. The glass transition and decomposition temperature decreased with increasing number of extrusion passes. Polym. Eng. Sci. 44:487–495, 2004. © 2004 Society of Plastics Engineers.
Article
Extrudate swell behavior of polystyrene (PS) and linear low-density polyethylene (LLDPE) melts was investigated using a constant shear rate capillary rheometer. Two capillary dies with different design configurations were used, one being a single flow channel and the other being a dual flow channel. A number of extrudate swell related parameters were examined, and used to explain the discrepancies in the extrudate swell results obtained from the single and dual flow channel dies, the parameters including output rate and output rate ratio, power law index, wall shear rate, wall shear stress, melt residence time, pressure drop induced temperature rise, flow channel position relative to the barrel centerline, and the flow patterns. It was found in this work that the power law index (n value) was the main parameter to determine the output rate ratio and the extrudate swell between the large and small holes for the dual flow channel die: the greater the n value the lower the output rate ratio and thus decreased extrudate swell ratio. The differences in the extrudate swell ratio and flow properties for PS and LLDPE melts resulted from the output rate ratio and the molecular chain structure, respectively. The extrudate swell was observed to increase with wall shear rate. The discrepancies in the extrudate swell results from single and dual dies for a given shear rate were caused by differences in the flow patterns in the barrel and die, and the change in the melt velocities flowing from the barrel and in the die to the die exit. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1713–1722, 2003
Article
The use of untreated sawdust as a filler in poly(vinyl chloride) (PVC) was examined—the effects of sawdust content on structural and thermal changes, and rheological and mechanical properties being of main interest. The results revealed that the torque and die entrance pressure drop values during mixing were independent of sawdust particles up to 23.1 wt%. The extrudate swell monotonically decreased up to 33.3 wt% sawdust content. Smooth wood-like texture with controllable size of the extrudate could be obtained at a sawdust content greater than 33.3 wt%. Tensile, impact, flexural and hardness properties of the PVC/sawdust composites considerably decreased with up to 16.7 wt% sawdust content before leveling off for higher sawdust loadings. The composites having sawdust higher than 16.7 wt% showed a benefit of cost savings. The decreases in the mechanical properties of PVC with sawdust are explained in association with the presence of moisture, interfacial defects between fibre and polymer, and fibre dispersions in the PVC matrix. Thermal degradations of PVC in PVC/sawdust composites were evidenced by a decrease in decomposition temperature and an increase in polyene sequences, which were caused by Cl cleavage due to strong hydrogen bonds of fibre–PVC molecules. The maximum of tanδ transition and the glass transition temperature were found to improve with sawdust content as a result of re-formation of hydrogen bonds between the macromolecules of the fibre and the polymer. The overall results in this work suggest that the properties of PVC/sawdust composites were strongly influenced by sawdust content up to 16.7 wt%. Beyond this value the effect of sawdust content on the properties was comparatively small. Copyright © 2003 Society of Chemical Industry
Article
This article concerns the effectiveness of MAH-PP copolymers (graft copolymer of PP and maleic anhydride) as coupling agents in jute-polypropylene composites. The fiber treatment time and the MAH-PP concentration influenced the mechanical properties of the composites. Flexural strength of the composites with MAH-PP treated fibers was higher than that of unmodified fibers, and increased with fiber loading. The cyclic-dynamic values at an increasing load indicated that the coupling agent reduces the progress of damage. Dynamic strength (dynamic failure stress at load increasing test) of the MAH-PP modified composites is therefore raised by about 40%. SEM investigations confirm that the increase in properties is caused by improved fiber-matrix adhesion. There was less inclination for fibers to pull out of the matrix.
Article
Natural fibres have proved to be an excellent reinforcement in polymers. The main disadvantage of the natural fibres to be used as reinforcement in polymers for structural applications is their hydrophilic nature. Oil palm fibres have been found to be an excellent reinforcement in phenolic matrices. A detailed investigation on the water sorption characteristics of oil palm fibres has been carried out. Various fibre surface modifications such as mercerization, latex coating, gamma irradiation, silane treatment, isocyanate treatment, acetylation and peroxide treatment were tried to reduce the hydrophilicity and thereby decreasing the sorption characteristics. The effects of treatments on the sorption characteristics of oil palm empty fruit bunch fibre in distilled water at four different temperatures were investigated. Changes in physical and chemical modifications of fibres upon different treatments changed the water sorption behaviour. Treatment reduced overall water uptake at all temperatures. Hydrophilicity of the fibres decreased upon many modifications, which decreases water uptake. The effect of sorption on the mechanical performance of the treated and untreated fibres was also investigated. It was found that the mechanical properties of the fibres decrease upon sorption and regains on desorption.
Article
The aim of this paper is the improvement of the mechanical properties of natural-fibre-reinforced thermosets, as a result of optimization of the properties of tossa jute fibres by the use of an NaOH treatment process. By this process shrinkage of the fibres during treatment had significant effects on fibre structure and, as a result, on the mechanical properties of the fibres. The highest fibre strength and stiffness were reached by using isometric conditions (shrinkage=0%). The fracture mechanism of the fibre was also affected by the shrinkage state. Regarding fibre/matrix adhesion, the rougher surface morphology after NaOH treatment did not lead to any improvement. Composite strength and stiffness generally increased as a consequence of the improved mechanical properties of the fibres by NaOH treatment under isometric conditions. The Young's modulus of the composites was linearly dependent on fibre content for both untreated and treated fibre composites. The Young's moduli of composites with treated and untreated fibres were approximately 30% and 50%, respectively, lower than for comparable glass-fibre/epoxy composites. The improvement in dynamic modulus (measured in an increasing-load test) of the composites as a result of the use of treated fibres was similar to that observed for Young's modulus. Furthermore, the use of treated fibres and of higher fibre contents, both led to a decrease in fatigue behaviour and progress in damage in the composites. Impact damping was distinctly affected by the shrinkage state of the fibres during the NaOH treatment because of its influence on yarn toughness. A good correlation was found between composite impact damping and yarn toughness for the jute/epoxy composites investigated.