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Pelletized cellulose fibres used in twin-screw extrusion for biocomposite manufacturing: Fibre breakage and dispersion
Abstract
Pelletizing is effective in compacting cellulose fibres, but it also causes fibre breakage and poor dispersion due to increased hydrogen bonding. This study investigated whether fibre dispersion and length could be improved by the addition of a lubricant, a commonly used composite processing aid, into cellulose pellets, or by using pelletized fibres that have not been completely dried to reduce hydrogen bonding. Cellulose pellets with different lubricant and moisture contents were prepared and compounded using twin-screw extrusion with polypropylene with 5 wt% fibre and 50 wt% fibre contents. The fibre dispersion, morphology and mechanical properties of the prepared composites were analysed. Dispersion and composite strength were improved with the addition of 4–6 wt% of lubricant while moisture had a negative effect on both properties. This study demonstrated that pelletization in the presence of a lubricant is a promising way to compact cellulose fibres and enable their continuous processing into biocomposites with improved mechanical properties.
... However, the successful preparation of an RF-reinforced TMC that satisfies increasingly demanding applications has proven challenging. First, RF possesses inherent limitations for use in TMCs, such as high moisture uptake, poor compatibility with non-polar matrices, limited thermal stability, and low bulk density, which results in challenging dosing during processing [1][2][3][4][5][6]. The latter limitation is often overcome by compressing the fibres into pellets, which solves the dosing issues but results in decreased dispersion and fibre damage [5,[7][8][9]. ...
... First, RF possesses inherent limitations for use in TMCs, such as high moisture uptake, poor compatibility with non-polar matrices, limited thermal stability, and low bulk density, which results in challenging dosing during processing [1][2][3][4][5][6]. The latter limitation is often overcome by compressing the fibres into pellets, which solves the dosing issues but results in decreased dispersion and fibre damage [5,[7][8][9]. Second, there are concerns about ensuring a consistent quality of composites due to year-to-year fluctuation in the properties of renewable materials and emissions of volatile organic compounds (VOC) in final applications [10,11]. ...
... Furthermore, their sides are relatively thin and can easily break during processing. A very important consideration is that the fibres were first compressed by a pelletising process, which makes compounding significantly less challenging and more consistent but is known to result in fibre damage and impede fibre dispersion [5,[7][8][9]. Thus, the results may have been different if the composites were produced from uncompressed pellets fed using a suitable dosing system. ...
This study investigated the influence of viscose fibre (VF) geometry on the microstructures and resulting properties of high-density polyethylene (HDPE) composites. Seven types of viscose fibres varying in cross-section shape, linear density, and length were pelletised, compounded into HDPE with a twin-screw extruder, and injection moulded. The microstructures of the composites were characterised by investigating their cross-sections and by extracting the fibres and measuring their lengths using optical microscopy (OM). The mechanical and thermal properties of the composites were characterised using differential scanning calorimetry (DSC), tensile tests, Charpy impact tests, and dynamic mechanical analysis (DMA). The composites prepared using cylindrical fibres with a linear density of 1.7 dtex exhibited the best fibre dispersion, highest orientation, and lowest fibre–fibre contact area. The decrease in the linear density of the cylindrical fibres resulted in increasingly worse dispersion and orientation, while composites containing non-cylindrical fibres exhibited a comparably larger fibre–fibre contact area. The initial fibre length of about 3 to 10 mm decreased to the mean values of 0.29 mm to 0.41 mm during processing, depending on the initial geometry. In general, cylindrical fibres exhibited a superior reinforcing effect in comparison to non-cylindrical fibres. The composites containing cylindrical fibres with a linear density of 1.7 dtex and a length of 5 mm exhibited the best reinforcing effect with an increase in tensile modulus and strength of 323% and 141%, respectively.
... The authors reported the reduction in fiber breakage and the increased dispersion of the fibers with the addition of a lubricant. Introducing the lubricant directly to the cellulose fiber pellets increased the mechanical properties of the composite as compared to adding lubricant while melt compounding [233]. Depending on the product, single-or double-screw extruders are used. ...
... The plasticity of the rigid cell wall can be enhanced by altering its composition, which might improve the processability of wood-plastic composites (WPCs) [18]. Previous research has used extrusion to manufacture biocomposites [228][229][230][231][232][233]. Gupta et al. [228] used hemp powder as a filler to reinforce reinforced polybutylene adipate-co-terephthalate (PBAT) for producing PBAT-HP biocomposite via extrusion. ...
... Silva et al. [232] successfully produced polyvinylidene fluoride-hydroxyapatite composite filaments at various angular velocities-by twin screw extruder and found that the produced filaments were suitable for 3D printing. Hietala et al. [233] found that pelletizing cellulose fibers with the help of a lubricant is a potential method for compacting them. The authors reported the reduction in fiber breakage and the increased dispersion of the fibers with the addition of a lubricant. ...
Global environmental concerns, as well as the rapid depletion of non-renewable fossil fuel-based resources, have prompted research into the development of sustainable, environmentally friendly, and biodegradable materials for use in a variety of high-end applications. To mitigate the environmental setbacks caused by nonbiodegradable materials, the development of biocomposites with improved mechanical performance is gradually gaining momentum. Natural fibers such as hemp, flax, and sisal have been well incorporated into biocomposite development. Nonetheless, the impact of functional moieties in their life cycle cannot be underestimated. In this review paper, a detailed discussion of the characteristics and components of biocomposites is presented. The treatment of composite materials (alkali and acetylation), as well as several manufacturing processes (hand layup, 3D printing, extrusion, etc.) and the applications of biocomposites, which are not limited to the aerospace industry, packaging, biomedicine, etc., are presented. Biocomposites with excellent durability, performance, serviceability, and reliability must be produced to expand their applications.
... Compacting the fibres into pellets using pelletizing process has proven to be a suitable technique to overcome this challenge, but it also comes with its drawbacks as fibre pellets are harder to disperse in a polymer matrix and pelletizing can lead to the shortening of fibres. The addition of lubricants to fibres before the pelletizing process can decrease the aforementioned negative effects associated with fibre pelletizing (Jacobson et al., 2001;Hietala and Oksman, 2018). CF are not well thermally stable and can start to degrade during melt blending with polymers which leads to the formation of low molecular products (Yang and Kokot, 1996;Feldmann, 2016). ...
... These differences were ascribed to better dispersion of untreated fibres as discussed in chapter 3. 1. Furthermore, pelletizing process could shorten the fibres due to mechanical forces, which also reflects in decreased strength of the composites (Hietala and Oksman, 2018). The addition of lubricant to the pellets resulted in a higher increase of σm (+ 11 %), which can be explained by enhanced dispersion or less damage to the fibres due to the presence of lubricant (Hietala and Oksman, 2018). ...
... Furthermore, pelletizing process could shorten the fibres due to mechanical forces, which also reflects in decreased strength of the composites (Hietala and Oksman, 2018). The addition of lubricant to the pellets resulted in a higher increase of σm (+ 11 %), which can be explained by enhanced dispersion or less damage to the fibres due to the presence of lubricant (Hietala and Oksman, 2018). The addition of HDPE-g-MA to the composites prepared directly from fibres resulted in the highest value of σm (+ 73 %), while HDPE-g-MA had only a slight effect on σm when added to the composites prepared from lubricated pellets. ...
In recent years, biocomposites have gained increasing attention in both industry and academia as a promising sustainable alternative to conventional composites. While the application range of biocomposites is continuously increasing, they are still very little used as food contact materials. The aim of the present study was to investigate the suitability of viscose fibres as reinforcement in thermoplastic biocomposites intended for food contact applications. Viscose fibres were compounded into biobased high-density polyethylene (HDPE) using a co-rotating twin-screw extruder and test specimens were injection moulded. Biocomposites were prepared using untreated and pelletized viscose fibres and the effect of the addition of compatibilizer and lubricant was investigated. Morphological, mechanical, rheological and migration properties of the prepared samples were characterised. Untreated fibres exhibited a significantly higher reinforcing effect than pelletized fibres due to better dispersion. The addition of a compatibilizer resulted in enhanced interfacial adhesion and fibre dispersion, which was reflected in increased tensile strength. The overall migration of all studied compositions was well below the permitted level, while the addition of a compatibilizer resulted in a strong acidic flavour in sensory tests, which is not permissible in food contact applications. The results showed that viscose fibres are a promising candidate for the preparation of thermoplastic biocomposites for food contact applications.
... 96,97 This minimizes fiber breakage and improves particle dispersion. 98 The mixtures were compounded by heating the barrel temperature of the double-screw extruder progressively from 200°C at the hopper to 185°C at the die. Cooling in a water bath followed by palletization into 3 mm granules was performed. ...
... Moisture was mitigated through a two-step drying procedure: air-drying for 5 days, then oven-drying at 100°C for 1 h. [98][99][100] Injection molding parameters were set at 195°C and 30 MPa, with cooling at 25°C for 15 s. 5 Testing specimens were obtained through injection molding for tension (ASTM D638), compression (ASTM D695), and flexural (ASTM D790) tests. ...
This study explores a relatively under-researched area concerning the influence of loading rate on the flexural properties of particulate-filled bio-composites and the effects of incorporating natural particles on their damage parameters. To investigate these aspects, three-point flexural tests were conducted across a range of bending speeds from 0.1 mm/s to 10 mm/s. The material under study consisted of Acrylonitrile-Butadiene-Styrene (ABS) reinforced with hemp particles at varying contents (1–10 wt%). Additionally, the impact of hemp particle incorporation on the damage parameters of ABS was evaluated through cyclic loading-unloading tension tests. The flexural test results demonstrated a consistent increase in the flexural modulus of ABS with rising strain rates, irrespective of the hemp particle content. In contrast, the percentage reduction in flexural strength exhibited a diminishing trend as the bending rate increased. Findings from the cyclic loading-unloading tension tests further revealed that the addition of hemp particles intensifies the degradation of ABS’s elastic modulus, with this effect becoming more pronounced at higher particle contents. Finite element simulations incorporating the experimentally determined damage parameters successfully reproduced the flexural load-displacement curves of the materials at different strain rates. These simulations corroborated the experimental findings and offered insights for optimizing material performance.
... Therefore, good mixing and high shear stresses are required for the efficient dispersion of CeF. Another important aspect is that in the present study, fibres were in the form of pellets that are much easier to dose but are known to result in poor fibre dispersion, even when processed with a twin-screw extruder [24][25][26]. The dispersion of CeF in the FDC process could therefore potentially be improved by using stiffer CeF, direct dosing of ...
... Therefore, good mixing and high shear stresses are required for the efficient dispersion of CeF. Another important aspect is that in the present study, fibres were in the form of pellets that are much easier to dose but are known to result in poor fibre dispersion, even when processed with a twin-screw extruder [24][25][26]. The dispersion of CeF in the FDC process could therefore potentially be improved by using stiffer CeF, direct dosing of uncompressed fibres using a gravimetric dosing system capable of handling low-bulk density materials, or by using a specially designed screw geometry with good dispersive and distributive mixing capabilities. ...
This study reports on the development of a novel polymer processing approach that combines low-temperature (LT) processing and fibre direct compounding (FDC) to reduce the thermal stress on thermosensitive components that occurs during compounding and subsequent injection moulding (IM). Composites based on polyamide 6 (PA6) and cellulose fibres (CeF) were prepared using an LT-FDC process and in parallel with a conventional approach using a twin-screw extruder and IM. The morphological, optical, thermal, and mechanical properties of the prepared samples were investigated using optical microscopy (OM), differential scanning calorimetry (DSC), colorimetry, dynamic mechanical analysis (DMA) and tensile tests. Composites prepared using LT-FDC exhibited worse fibre dispersion but lower fibre degradation. In comparison to neat PA6, the LT-FDC composites had increased tensile modulus (Et) and storage modulus (E′) at 120 °C by up to 32% and 50%, respectively, while the tensile strength (σm) decreased by 20%.
... The higher melt viscosity of the samples containing lubricants suggests an improved interaction between the fibers and the matrix, which has also been observed in composites where the lubricants tend to behave as compatibilizers at low contents. [13,35] The higher viscosity of the TMP-based samples containing MoS 2 may be due to the ability of MoS 2 to interact with the aromatic structure of the lignin present in the TMP. [15] In case of the DP-based samples, which have a negligible lignin content, the addition of MoS 2 showed no variation in the melt viscosity and it behaved more like a lubricant. ...
... In the presence of the TMP fibers, however, the lubricants behaved like a compatibilizer at low concentrations and had a lubricating effect at higher concentrations. [13,35] When the MgSt content was increased to 5 wt% in the TMP30-containing composite, the viscosity profile was same as that of the samples containing 1.5 wt% MgSt. With 5 wt% MoS 2 , a slight reduction in the viscosity was however observed, as shown in Figure 6(B). ...
Compression molded composites were prepared through a water‐assisted mixing of an aqueous suspension of poly(ethylene‐co‐acrylic acid), additive, and pulp fibers [thermomechanical pulp (TMP) or dissolving pulp (DP)]. The lubricating additives used were magnesium stearate (MgSt) and molybdenum disulphide (MoS2). The composite materials had dry pulp contents ranging from 30 to 70 wt% and 5 wt% additive relative to the weight of the pulp. The adsorption of the additives onto the fibers was confirmed by scanning electron microscopy and energy dispersive X‐ray analysis. DMA showed that MgSt and MoS2 gave similar interphase properties for the TMP samples at all loading contents, but the combination of MgSt and MoS2 improved the overall properties of the DP‐based composites. The tensile modulus, at 70 wt% fiber content (TMP or DP), increased compared to the matrix by a factor of 6.3 and 8.1, without lubricants, and by a factor of 8 and 10.7, with lubricants, respectively. The increase in melt viscosity observed for the lubricated samples was greater for the TMP‐based samples containing MoS2. At a lubricant content of 5 wt%, in 30 wt% TMP, the MoS2 behaved as both a lubricant and compatibilizer.
... 23 In another study, Hietala and Oksman analyzed the effect of lubricants and different moisture contents of cellulose on fiber breakage and dispersion, and 4−6 wt % of lubricants improved the performance of pelletized cellulose fibers as reinforcement in polypropylene, resulting in a better dispersion with a higher solid content. 25 Similarly, Taheri et al. reported the defibrillation of cellulose fibers using one-step twin-screw extrusion. 26 Cellulose pulp was compounded with hydroxyethyl cellulose (HEC) using one-step TSE to defibrillate the cellulose and produce biocomposites in the same process. ...
... However, we believe this could be improved by using a coupling agent, such as maleic anhydride grafted PP (MAPP). 25 ...
Bio-based wood materials are preferable for composites because of their sustainability, but adequately dispersing wood fibers in polymers can be difficult and costly. Our approach was to pretreat the wood with a green solvent system, allowing the composite to be extruded in a single step, simplifying the process, and reducing the overall cost. This study investigates the fibrillation of untreated wood sawdust (W) and deep eutectic solvent-treated wood sawdust (DESW) using a one-step twin-screw extrusion (TSE) process. The results of the analysis of wood fractions and optical microscopy confirmed that the one-step extrusion process resulted in fibrillation of both treated and untreated wood material. The width of the original wood particles was reduced by more than 99% after a one-step TSE for both untreated and DES-treated wood. The size reduction of the DESW was slightly greater than that of the untreated wood, and fibrillation was further confirmed by rheological analysis. The fibrillated wood was then compounded with polypropylene (PP) to produce a wood fiber-polypropylene composite with 50 wt % wood content. The elastic modulus of both untreated and treated extruded composites was higher than that of neat PP. The tensile strength and strain at break for the DESW-PP composite slightly increased in comparison to the untreated W-PP composite. Furthermore, DES treatment of wood resulted in a darker color and increased hydrophobicity of the material.
... However, the CF-HEC biocomposite obtained by simultaneous extrusion of CF and HEC (one-step TSE) does not need to be redispersible to be used in continuous industrial applications. On the one hand, the twin-screw extrusion (TSE) method can be an alternative method for pelletizing fibrillated CFs and different polymer matrices (Suzuki et al. 2013) or biopolymeric materials (Hietala et al. 2011b;Hietala and Oksman 2018;Haque et al. 2018). On the other hand, the fibrillation of the CFs and the mixing of the fibers and biopolymer matrix can be improved at the same time with the use of TSE. ...
... In this study, the length reductions of 50%, 70%, and 69% were calculated for EX-50CF, EX-65CF, and EX-80CF, respectively. It has been reported that extrusion can result in fiber breakage (Le Baillif and Oksman 2009;Hietala and Oksman 2018), and the results presented in Table 3 also show the length reduction after extrusion. The aspect ratios were also decreased from 56 for the neat CF to 32-47 for the extruded CF. ...
In this work, the defibrillation of cellulose fibers (CF) in the presence of hydroxyethyl cellulose (HEC) within the one-step twin-screw extrusion (TSE) process was examined. The effect of the TSE on cellulose fiber size reduction as well as CF-HEC biocomposites properties were investigated. The results showed that the TSE of cellulose fiber-hydroxyethyl cellulose (CF-HEC) with different cellulose fiber contents (50, 65, and 80 wt%) resulted in partial defibrillation of the cellulose fibers. The fractionation test of the cellulose fibers confirmed that their size was reduced and some fibrillation was observed in microscopy studies. The maximum width reduction of 46% occurred with 80 wt% cellulose content. However, the partial width reduction was also observed with 50% and 65 wt% of cellulose contents. Based on rheological measurements, the shear-viscosity trend of CF-HEC dispersion abruptly dropped when higher fiber content (80 wt%) was extruded, which was related to the fibrillation of the cellulose fibers as well as the reduction of the length. The extruded CF-HEC materials (powder form) were compression molded to prepare the biocomposites with different cellulose fiber contents (50, 65, and 80 wt%). The extruded CF-HEC powders were diluted with addition extra HEC to make biocomposites with lower fiber content (20%, 30%, and 40 wt%) and compression molded to study how the size reduction of the cellulose fibers affected the mechanical properties of biocomposites. The results showed that the E-modulus improved from 0.4 GPa of the neat HEC to 1.6 GPa for the composite with 40 wt% CF. Interestingly, the tensile strength of CF-HEC biocomposite with 40 wt% confirmed a clear improvement from 9.8 to 26.6 MPa, confirming good interaction between HEC and CF.
Graphic abstract
Preparation (mixing, TSE, and hot-pressing) and characterization (FE-SEM, rheometry, and tensile test) of CF-HEC biocomposite
... These cellulosic particles were filled in polymer matrix to develop micro or nanocomposites, depending upon the size of the cellulosic particle fillers. In general, most of the literature focused on the addition of cellulosic particles in thermoplastic polymeric matrices, such as PP (polypropylene), LDPE (low density polyethylene), PLA (Polylactic acid), etc., [31][32][33][34]. The literature on cellulosic particles filled in thermoset polymers are relatively scarce or negligibly available [35]. ...
... Since the material was extracted from natural source such level inconsistence properties are expected. Similar results were also obtained elsewhere [8,31,33]. ...
In recent years, much attention was focused on developing green materials and fillers for polymer composites. This work is about the development of such green nanofiller for reinforcement in epoxy polymer matrix. A cellulose nanofiber (CNF)-filled epoxy polymer nanocomposites was prepared in this work. The effect of CNF on curing, thermal, mechanical, and barrier properties of epoxy polymer is evaluated in this study. CNF were extracted from banana fiber using acid hydrolysis method and then filled in epoxy polymer at various concentration (0–5 wt.%) to form CNF-filled epoxy nanocomposites. The structure and morphology of the CNF-filled epoxy nanocomposites were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Curing studies shows CNF particles acts as a catalytic curing agent with increased cross-link density. This catalytic effect of CNF particles has positively affected tensile, thermal (thermogravimetry analysis and dynamic mechanical analysis) and water barrier properties. Water uptake test of nanocomposites was studied to understand the barrier properties. Overall result also shows that the CNF can be a potential green nanofiller for thermoset epoxy polymer with promising applications ahead.
... Figure 4(a) represents the DSC curves of the PP/MCF/xGNP/SG composite at different processing parameters, with a baseline shift at ~200 °C and an endothermic peak at 455 °C. Based on the enlarged curve images displayed in Figure 4(b), it can be seen that the composite encountered an earlier endothermic peak at ~168 °C, because the polypropylene resin started to melt [38]. The melting temperature of the polypropylene, used in this study, was slightly higher (~168 °C) because of its nano-sized powder, compared to standard polypropylene (~160 °C ) [39]. ...
... Differential scanning calorimetric studies were conducted, in order to understand the effect of the composite properties on the melt temperature. Figure 4a represents the DSC curves of the PP/MCF/xGNP/SG composite at different processing parameters, with a baseline shift at~200 • C and an endothermic peak at 455 • C. Based on the enlarged curve images displayed in Figure 4b, it can be seen that the composite encountered an earlier endothermic peak at~168 • C, because the polypropylene resin started to melt [38]. The melting temperature of the polypropylene, used in this study, was slightly higher (~168 • C) because of its nano-sized powder, compared to standard polypropylene (~160 • C) [39]. ...
Polymer composites have been extensively fabricated given that they are well-fitted for a variety of applications, especially concerning their mechanical properties. However, inadequate outcomes, mainly regarding their electrical performance, have limited their significant potential. Hence, this study proposed the use of multiple fillers, with different geometries, in order to improve the electrical conductivity of a polymer composite. The fabricated composite was mixed, using the ball milling method, before being compressed by a hot press machine at 3 MPa for 10 min. The composite plate was then measured for both its in-plane and through-plane conductivities, which were 3.3 S/cm, and 0.79 S/cm, respectively. Furthermore, the experimental data were then verified using a predicted electrical conductivity model, known as a modified fibre contact model, which considered the manufacturing process, including the shear rate and flow rate. The study indicated that the predicted model had a significant trend and value, compared to the experimental model (0.65 S/cm for sample S1). The resultant fabricated composite materials were found to possess an excellent network formation, and good electrical conductivity for bipolar plate application, when applying compression pressure of 3 MPa for 10 min.
... The use of lignocellulose natural fibers, as reinforcement of composites, has grown greatly, because it meets the demands of sustainability, as stated before, since they are inexpensive, renewable and biodegradable (Ninomiya et al., 2017). Besides that, lignocellulose fibers have low density, competitive mechanical properties and low cost, which make them an attractive ecological alternative to glass synthetic fibers (Hietala and Oksman, 2018). The disadvantages of natural fibers remain in the low compatibility with hydrophobic polymer matrices, more limited processing temperatures and higher heterogeneity (Pappu et al., 2019;Zhang et al., 2017;Zhang and Li, 2016). ...
... The use of agricultural residues is of special interest since it combines the possibility of more worthy destination for these materials, with the fact that it is not necessary to burn or decompose these wastes, so providing a low-cost alternative to wood fiber composites (Ardanuy et al., 2012). These lignocellulose materials are mainly composed of cellulose, hemicellulose, lignin and pectin, with a small quantity of extractives and they are often ground into smaller particles to facilitate the feeding into the processing equipment (Hietala and Oksman, 2018;Xie et al., 2010). ...
This study aims to analyze the influence of an agricultural residue, yerba mate (YM), on thermal and thermo-mechanical behavior of virgin polypropylene (PP) and post-consumer polypropylene (rPP) matrix material. 20, 30 and 40 wt.% of YM were loaded into PP and rPP by extrusion, followed by injection molding to prepare the specimens. TGA results showed that rPP composites had better thermal stability, which is in accordance with the crystallinity index obtained by DSC analysis. This analysis revealed that the crystallinity of rPP matrix composites showed no significant changes as YM fibers were added, as opposed to the virgin PP matrix composites, which showed a decrease in crystallinity. In addition, DMA and SEM analysis revealed comparable thermo-mechanical performance and better homogeneity of the rPP in relation to virgin PP composites. These results indicate a potential application of these "green composites" with additions of up to 40 wt.% of YM residues.
... Así, la innovación en la producción de arena para gatos a partir de biomasa como el bagazo de caña no solo demuestra el potencial de los residuos agrícolas para ser transformados en productos útiles y rentables, sino que también promueve prácticas industriales más sostenibles y respetuosas con el medio ambiente. Este enfoque integrado hacia la utilización de recursos renovables no solo beneficia a las industrias energéticas y de consumo, sino que también contribuye positivamente a la reducción de residuos y a la mitigación del impacto ambiental global (19). ...
El propósito de este trabajo es explorar la reutilización del bagazo de caña de azúcar, un subproducto agrícola, en aplicaciones ecológicas, específicamente como arena sanitaria para gatos. El problema principal radica en la necesidad de encontrar alternativas sostenibles a los productos tradicionales de arena, que generan un alto impacto ambiental. El objetivo de esta investigación fue analizar las propiedades del bagazo, compararlo con arenas convencionales, y desarrollar un prototipo de arena sanitaria ecológica. La metodología utilizada incluyó una revisión sistemática de la literatura científica, basada en fuentes de bases de datos reconocidas como Scopus y Scielo. Se analizaron estudios previos sobre las propiedades fisicoquímicas del bagazo y su aplicabilidad como material biodegradable. Además, se realizaron pruebas comparativas entre la capacidad de absorción y aglutinación del bagazo frente a las arenas tradicionales. Los resultados indicaron que el bagazo de caña de azúcar presenta una capacidad de absorción superior (85%) y una mayor biodegradabilidad (95%) en comparación con la arena convencional (15%). Además, se logró reducir los olores en un 65%, lo que demostró su efectividad como arena sanitaria ecológica. En conclusión, el uso del bagazo de caña de azúcar como arena ecológica ofrece una alternativa sostenible y económicamente viable, reduciendo el impacto ambiental de las arenas tradicionales y contribuyendo a la economía circular mediante la reutilización de desechos agrícolas.
... CF exhibited the lowest storage modulus due to fibre pull-out during the extrusion (filament making) process [29]. The explanation for this can be found in previous research, which indicated that poor surface properties lead to poor bonding within the fibre matrix and a subsequent deterioration in strength [30]. Hence, having single orientations and alignment covered by the polymer matrix could be an alternative to consider further. ...
The production of fabricated filaments for fused deposited modelling printing is critical, especially when higher loading filler (>20 wt.%) is involved. At higher loadings, printed samples tend to experience delamination, poor adhesion or even warping, causing their mechanical performance to deteriorate considerably. Hence, this study highlights the behaviour of the mechanical properties of printed polyamide-reinforced carbon fibre at a maximum of 40 wt.%, which can be improved via a post-drying process. The 20 wt.% samples also demonstrate improvements of 500% and 50% in impact strength and shear strength performance, respectively. These excellent performance levels are attributed to the maximum layup sequence during the printing process, which reduces the fibre breakage. Consequently, this enables better adhesion between layers and, ultimately, stronger samples.
... Metal coating of the carbon fiber made the fiber filament stiffer. Chopped NiCF could be easily exposed to the shearing force occurring between the barrel and the screw during compounding, as similarly found in other composite systems [37,38]. In the case of mainfeeding, chopped NiCF with the melted PA6 resin could move from the main-hopper entrance to the die-end of the extruder. ...
In the present study, how side-feeding of NiCF during twin-screw extrusion processing influences the fiber aspect ratio and thermal, mechanical, electrical, and electromagnetic properties of nickel-coated carbon fiber (NiCF)-reinforced polyamide 6 (PA6) composites was explored. For this, the fiber length distribution, thermal stability, heat deflection temperature, dynamic mechanical property, tensile, flexural, electrical resistivity, and electromagnetic interference shielding effectiveness (EMI SE) properties of NiCF/PA6 composites were extensively investigated. Chopped NiCF was regularly fed via either a main feeder or a side feeder and NiCF/PA6 pellets with different fiber-feeding pathways were prepared. The side-feeding effect of NiCF on the fiber length distribution and the composite properties was studied. The thermal stability, heat deflection temperature, storage modulus, tensile, flexural, and surface resistivity, and EMI SE properties of the NiCF/PA6 composites strongly depended not only on the NiCF content but also on the feeding method (main-feeding or side-feeding) upon extrusion processing, indicating that the fiber length distribution relevant to the fiber aspect ratio was critically important to enhance the composites’ properties. As a result, the NiCF/PA6 composites produced via side-feeding of NiCF exhibited an NiCF distribution longer than that produced via main-feeding, leading to enhancement of the thermal stability, heat deflection temperature, storage modulus, tensile, flexural, and EMI SE properties, strongly depending on the NiCF content.
... CNFs form filamentous web like networks, with high flexibility, inducing to the materials they are added, high strength and high deformation properties (Li et al., 2014). CNFs have been used for bio-composite manufacturing in various industrial sectors, such as the automobile industry to fabricate interior parts, outdoor decking materials, thermosets (Saba et al., 2017b) and other consumer items (Hietala and Oksman, 2018). Nanocellulose can be found in the form of nanocrystals (CNCs) and nanofibers (CNFs) (Xu et al., 2013) and is also widely used as reinforcement material in composites (Barari et al., 2016a;Kowalczyk et al., 2011;Vidakis et al., 2021a;Zandi et al., 2020). ...
The effect of Cellulose NanoFiber (CNF) addition to a medical-grade resin in Stereolithography (SLA) Additive Manufacturing (AM) technology is reported, aiming to elaborate an easily processable, highly stiff bio-compound. CNFs were shear stir blended at various weight ratios with liquid resin. The fabricated nanocomposite materials were introduced in an SLA 3D printer for specimens manufacturing. The mechanical performance was studied according to international standards. Charpy Toughness and Vickers microhardness were calculated for all tested materials. A microscopic and surface analysis was conducted on fractured tensile specimens by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy
(AFM), respectively. The thermal and thermomechanical properties were investigated by Thermogravimetric Analysis (TGA), Differential Calorimetry (DSC), and Dynamic Mechanical Analysis (DMA). Significant reinforcement of the medical-grade nanocomposites is reported, with the highest values calculated to be at 1.0 wt.% concentration (more than 100% at the tensile strength), while brittleness and rigidity were increased.
... In order to comprehensively determine the correlation of process parameters during compounding experimentally, a high level of testing, personnel and material expenditure is required [17,18]. To date, fiber length change in composites has primarily been determined by microscopic observation and X-ray microtomography of the samples [19][20][21][22][23]. To enable significant quality improvements, experimentally validated modeling is required that reaches far beyond the current state of technology and considers the details of the used machines and materials. ...
Due to their valuable properties (low weight, and good thermal and mechanical properties), glass fiber reinforced thermoplastics are becoming increasingly important. Fiber-reinforced thermoplastics are mainly manufactured by injection molding and extrusion, whereby the extrusion compounding process is primarily used to produce fiber-filled granulates. Reproducible production of high-quality components requires a granulate in which the fiber length is even and high. However, the extrusion process leads to the fact that fiber breakages can occur during processing. To enable a significant quality enhancement, experimentally validated modeling is required. In this study, short glass fiber reinforced thermoplastics (polypropylene) were produced on two different twin-screw extruders. Therefore, the machine-specific process behavior is of major interest regarding its influence. First, the fiber length change after processing was determined by experimental investigations and then simulated with the SIGMA simulation software. By comparing the simulation and experimental tests, important insights could be gained and the effects on fiber lengths could be determined in advance. The resulting fiber lengths and distributions were different, not only for different screw configurations (SC), but also for the same screw configurations on different twin-screw extruders. This may have been due to manufacturer-specific tolerances.
... Initially, the thermoplastics are shredded and pelletized (Zander et al., 2018). The pellets are then dried before processing, as this drying effect governs the flow behavior of plastics (Hietala and Oksman, 2018;Welker et al., 2018). If not appropriately dried before extrusion, it often leads to a non-uniform filament diameter, resulting in poor printing (Zander et al., 2018). ...
Plastics have emerged as one of the essential materials present on the planet. However, its accumulation can negatively impact the environment if not disposed of properly. To counter this issue, the ‘Circular Economy’ is one such economic growth model with one of the objectives of using plastic resources efficiently. Several plastic recycling methodologies have been derived, out of which Distributed Recycling via Additive Manufacturing (DRAM) is one of them. The main objective of this study aims to form an optimal link between two different areas of knowledge domains: plastic recycling and additive manufacturing. A scientometric analysis has been conducted to measure the former knowledge domains mentioned to accomplish this goal. From the results, the Scopus database yields 1452 relevant publications between 2013-2021. The results suggest that Fused Deposition Modeling (FDM) is the most used AM technology on recycled plastics. Hence, the review targets the FDM process in the context of plastic recycling. A critical review has been done, which shows the material characterization of recycled polymers in AM. This is followed by an in-depth analysis of the FDM technology, including discussions on influencing parameters of this process. The following results present the multi-material mixing of plastics and Direct FDM systems and their relevance in plastic recycling. These two areas create opportunities to increase the variety of feedstock materials that can be 3D printed. Lastly, the authors have proposed some future directions based on the literature review done in this work.
... Moreover, it is important to note that the lignocellulosic fiber lengths reported in Table 3 correspond to the lengths of the fibers after compounding. Compounding reduces the fiber length as demonstrated by [30,119,141]. In addition, one may expect that similar damage may apply for CNFs, meaning that they may be structurally modified after compounding [144]. ...
Biocomposites based on lignocellulosic components (e.g. pulp fibers, nanocellulose and lignin) are of interest as sustainable replacements for thermoplastic fossil-based materials, which find their application in household items, construction, automotive, 3D-printing, etc. Nanocellulose, a nano-structural component of pulp fibers, is considered having potential as a high-performance reinforcement for bioplastics, due to its high aspect ratio and potentially strong mechanical properties. Lignin, a biodegradable polymer isolated from pulp fibers, can be considered as an essential bio-resource for the production of biocomposites, due to the aromatic structure and functional groups. In this review the reinforcing ability of selected lignocellulosic components and their applicability in 3D-printing is presented, considering their mechanical properties. At this point, there are challenges in processing nanocellulose that may reduce its attractiveness as a reinforcement in thermoplastic biocomposites. The objective of the review is to identify current challenges and opportunities for the application of 3D-printed lignocellulosic biocomposites. Optimization of 3D printing process parameters are considered to be a key to further improve the mechanical properties of the end product. Importantly, this review revealed that greater efforts in mechanical fatigue research may contribute to assess and improve the potential of lignocellulosic reinforcements for structural applications.
... In the second method, fibers, resins, and related additives are compounded in the extruder, and the compounded material is shaped into a final product by injection or compression molding. With those methods, fibers are usually chopped and mixed with the polymer matrix in either thermokinetic mixers or mixing chambers to blend them before entering in twin-screw extruders, and these methods are considered not adequate for an industrial scale [2,3]. The polymer pellets and chopped fibers are fed and transported into the screw, compressed by the feeding forces, and shaped by a solid plug, which thoroughly fills the screw channel [4]. ...
This study aimed to develop an extrusion and pultrusion system for producing carbon fiber-filled thermoplastic pellets. The extruder delivers a plastic melt to an impregnation die in sufficient volume and is pulled out along with the fibers. The fibers pass in a sideways stretched condition through spreader pins attached in the melt pool, which can then be wetted optimally. The wetting effect was also improved by immersing fiber in a coupling agent solution at an elevated temperature before feeding to the extruder die. For machine performance testing, polypropylene was used as a matrix resin with the following parameters: a screw speed of 5 rpm, a die temperature of 210 °C, and a pulling speed of 56 mm/s. The pull-out test was conducted to assess the interfacial shear strength (IFSS) between fibers and matrix. Scanning electron microscopy (SEM) was applied to characterize the quality of fiber impregnation. SEM characterized a good bonding performance between carbon fiber and the matrix. The average IFSS of the results indicated a good resistance of fiber–matrix bonding against a pulling force. It proved that the combination of the extrusion–pultrusion system can produce high-quality filaments as a raw material of composite pellets.
... Typically, short glass fiber reinforced PP are produced using a twin-screw extruder in which the matrix and chopped fibers are melt-mixed in the extruder. During extrusion, the high shear forces lead to major fiber breakage [10][11][12]. On the other hand, Long Fiber Thermoplastic (LFT) are molded using pellets where the reinforcing fibers are as long as the pellet length. ...
The aim of this study was to investigate the length variation effect of flax/polypropylene (flax/PP) pellets on the quality of injection molded final product. Pultruded rods of 4.76 mm in diameter were produced using multi-die pultrusion. The fiber volume content of the rods was 50% and the void content was around 3.5%. Rods were pelletized in three different lengths of 6, 9 and 15 mm. Three sets of dogbones coupons were injection-molded using the three different pellet sizes. The flax/PP pellets were blended with polypropylene in the injection molding machine to lower the fiber weight fraction to 25%. The injected dogbones were characterized by tensile and charpy impact tests to evaluate the mechanical strength. The impregnation quality and fiber distribution in pultruded rods were characterized by void content measurements, and optical microscopy. Results showed that pellets from the well consolidated pultruded rods were consistent in shape and size. The flax fiber distribution into the injected dogbones was uniform, whatever pellet length used. Finally, the usage of longer pellets significantly increased impact strength of the injected coupons. Tensile properties were also slightly improved when longer pellets were used.
... However, it also leads to fiber breakage or fiber length reduction which weakens the mechanical properties [30]. Hietala et al. [31] reported that the use of lubricant would be helpful for reducing fiber breakage for twin-screw compounding of WPC. It was also reported that direct injection molding can be used to avoid high-shear mixing, reduce cycle time, and improve production efficiency [24,25,32,33]. ...
Wood-plastic composites (WPC), made of wood fiber (WF) and thermoplastics, have been well developed and commercialized in construction, packaging, automotive, and furniture industry over the past three decades, as they are environmentally friendly and require less maintenance compared with natural wood. Polypropylene (PP) is one of major thermoplastics used in WPC. However, the relatively poor mechanical properties of WPC prevent them from penetrating into other structural applications where strong mechanical properties are required. To enhance the mechanical properties of PP/WF composites, this paper applies one-step direct injection molding to produce the hybrid WPC with glass fiber (GF) and carbon fiber (CF). Compared with those of PP/WF composites, the tensile strength and tensile modulus of PP/WF/GF hybrid composites increased 30% and 26%, respectively, and the tensile strength and tensile modulus of PP/WF/CF hybrid composites increased 38% and 78%, respectively. Apart from the significant increase of mechanical properties, the additional benefit of hybrid WPC was that their flame-retarding property was improved. Particularly, the dripping behavior (or fire spreading) during burning associated with WPC was significantly reduced or eliminated for the hybrid composites. In addition, the water absorption and the surface roughness of hybrid composites were also studied. This study demonstrates that it is feasible to make hybrid WPC with one-step injection molding, and hybrid WPC open the door to their potential structural applications.
... The high shear rate in a twin-screw compounder or k-mixer typically leads to a good dispersion of fibers in the polymer matrix; however, it also leads to fiber breakage or fiber length reduction, which deteriorates the mechanical properties [41]. Hietala et al. [42] studied fiber breakage and dispersion for twin-screw extrusion of WPC and encouraged the use of lubricant during the compounding process. It was reported that direct injection molding can be used to avoid high-shear mixing and improve production efficiency [36,43,44]. ...
High-density polyethylene (HDPE) has been widely used to make wood–plastic composites (WPC) in the past decades for building materials, automotive, packaging, and furniture industry. However, the relatively poor mechanical properties have limited the applications of WPC. To address this issue, this study introduced a small of amount of lightweight and high-strength carbon fiber (CF) into the WPC matrix, to make hybrid composites through a cost-effective direct injection molding process. This paper investigated the mechanical properties and water absorption behaviors of hybrid HDPE composites with wood fiber (WF) and CF. Compared with WPC with the same fiber loading, the hybrid composites had 40% increase in tensile strength and 253% increase in tensile modulus. The effects of water absorption on the mechanical properties of hybrid composites were interpreted with two competing mechanisms (i.e., interfacial bond weakening and fiber swelling). This study implies that adding a small amount of CF to WPC in direct injection molding would be another approach for enhancing the mechanical properties without additional operating cost.
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... For example, Young's modulus of composites was improved by 10-20% (Ragoubi et al. 2012). The tensile properties of composites from pelletized cellulosic fibers (PCF) improve with the addition of lubricant (~ 5% of pellet) during the pelletization process and reduce the breakage of fiber; however, the presence of moisture in PCF has a negative impact on the tensile properties of composites (Hietala and Oksman 2018). ...
This study provides an overview of the application of biomaterials in automotive industries and their economic and environmental implications. It also discusses the recent developments, ongoing activities, and the major constraints that need to be addressed for commercial application. Innovative material selection and processing methods improve the environmental performance of biocomposite materials as well as their properties. Numerous efforts have been made in evaluating the environmental impacts of biomaterials; however, impacts of land use change have been left out, and the economic analysis has been conducted to a limited extent. A broader sustainability analysis is essential for its commercial applications and for any investment in biocomposite industries to alleviate environmental, economic, and safety risks. The proliferation of life cycle sustainability assessment and common material data system in the biocomposite industry may accelerate the acceptance of biocomposite, thus improving the potential social and environmental benefits.
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... For example, Young's modulus of composites was improved by 10-20% (Ragoubi et al. 2012). The tensile properties of composites from pelletized cellulosic fibers (PCF) improve with the addition of lubricant (~ 5% of pellet) during the pelletization process and reduce the breakage of fiber; however, the presence of moisture in PCF has a negative impact on the tensile properties of composites (Hietala and Oksman 2018). ...
This study provides an overview of the application of biomaterials in automotive industries and their economic and environmental implications. It also discusses the recent developments, ongoing activities, and the major constraints that need to be addressed for commercial application. Innovative material selection and processing methods improve the environmental performance of biocomposite materials as well as their properties. Numerous efforts have been made in evaluating the environmental impacts of biomaterials; however, impacts of land use change have been left out, and the economic analysis has been conducted to a limited extent. A broader sustainability analysis is essential for its commercial applications and for any investment in biocomposite industries to alleviate environmental, economic and safety risks. The proliferation of life cycle sustainability assessment (LCSA) and common material data system in the biocomposite industry may accelerate the acceptance of biocomposite, thus improve the potential social and environmental benefits.
... The proximate analysis of CCF and CHF is presented in CCF. This parameter is directly related to the dispersion of the fibers in a polymer matrix during the melting processing [39]. Higher moisture content causes lower dispersion of a lignocellulosic material in a polymer matrix. ...
Lignocellulosic materials, despite their abundance and attractiveness, have long been marred with challenges in optimising the cost-functionality-quality trade-off. This comprehensive authoritative review paper explores how various lignocellulosic feedstock have been utilised to prepare marketable and sustainable bioplastics, as potential substitutes to conventional petroleum-based packaging. Dependence on hydrocarbon-derived plastics is increasingly being supplanted by both consumer-driven and sustainability-oriented materials design. This comprehensive paper encompasses a broad review relating to recent research (2013−2023) on the innovations and heuristic approaches to modify lignocellulose for the production of packaging films. The review paper holds extensive focus across various lignocellulosic materials such as - but not limited to - cellulose nanomaterials, cellulose esters and grafted cellulose. Advances in processes reported to date such as mechanochemical, chemical, thermochemical, biochemical and other novel methods have been studied. The materials design and process implications in terms of its cost, energy input and sustainability in its true sense, for all known techniques have been extensively investigated in this review paper. The review paper has further provided an elaborate process-structure-property-performance framework that characterises how material properties could be fine-tuned via different process considerations. A techno-economic feasibility overview for said processes and materials' use is also described herein.
Natural fiber-reinforced biocomposites with excellent mechanical and biological properties have attractive prospects for internal medical devices. However, poor interfacial adhesion between natural silk fiber and the polymer matrix has been a disturbing issue for such applications. Herein, rigid-flexible agents, such as polydopamine (PDA) and epoxy soybean oil (ESO), were introduced to enhance the interfacial adhesion between Antheraea pernyi (Ap) silk and a common medical polymer, polycaprolactone (PCL). We compared two strategies of depositing PDA first (Ap-PDA-ESO) and grafting ESO first (Ap-ESO-PDA). The rigid-flexible interfacial agents introduced multiple molecular interactions at the silk-PCL interface. The "Ap-PDA-ESO" strategy exhibited a greater enhancement in interfacial adhesion, and interfacial toughening mechanisms were proposed. This work sheds light on engineering strong and tough silk fiber-based biocomposites for biomedical applications.
To reduce the reactant concentration necessary for producing a newly synthesized thermoplastic lignocellulose from forestry waste, this study explores the concept of a recycle stream as a chemical unit operation in a reactive extrusion process. Modified lignocellulose from the first pass was returned to the start of the extrusion process to act as a lubricant for the lignocellulose feedstock. By this action, a high lignocellulose content could be extruded without requiring costly lubrication alternatives such as plasticizing additives, solvents, or excessive quantities of liquid reactants. With 25% recycled material, a significantly improved processing state was found, allowing for a reduction in total reactant usage by 50% without change to the degree of modification and ultimately leaving less unreacted species in the final product. The thermoplastic nature of the modified lignocellulose was characterized by thermal and rheological analysis and was found to demonstrate greater flowability with any recycle stream fraction.
Composites in 25 kg batches were compounded of cellulose nanocrystals (CNC) and thermomechanical pulp (TMP) and shaped into caps at industrial facilities on a pilot‐plant scale. Some of the material was also injection molded into plaques to compare the effect of laboratory‐scale and pilot‐scale compounding of poly(ethylene‐co‐acrylic acid) (EAA7) and poly(caprolactone) composites reinforced with 10 wt% CNC and TMP. The materials compounded under laboratory‐scale conditions showed a different morphology, improved mechanical properties, and a higher viscosity, than the materials compounded on a pilot‐scale. In some cases, the rheological properties of the melts indicated the presence of a relatively strong percolating cellulosic network, and the interphase region between the cellulose and the matrix appears to be important for the mechanical performance of the composites. After the compounding on a pilot scale, both the length and width of the pulp fibers was reduced. The TMP provided better reinforcement than the CNC possibly due to the higher aspect ratio.
Cynara Cardunculus plant was used as source of seed oil. The epoxidized oil (ECO) and presscake waste fibers (CP) recovered from post-oil extraction, were recombined for developing PLA functional biocomposites, according to “zero waste” circular economy approach. Different compositions of PLA/CP and PLA/CP/ECO were prepared in form of platelets and investigated by thermal, morphological, structural and mechanical analyses. The poor interfacial adhesion between the hydrophobic PLA matrix and short, hydrophilic and randomly dispersed presscake fibers, well evidenced by morphological analysis, was responsible of PLA thermal degradation hastening, Tg decreasing and tensile properties dropping down, since no mechanical stress transfer occurred from the polymer to the dispersed phase. The inclusion of ECO slightly improved the above properties due to its mild compatibilizing action inducing a fairly tightening of the macromolecular structure. The recycling of CP waste fibers was effective in hastening the polymer biodegradation in common soil under environmental conditions. Indeed, biocomposites recovered after 90 days of soil burial tests evidenced morphological features typical of late stage PLA biodegradation, a drastic dropping down of molecular weights and a decreasing of PLA thermal stability. These experimental evidences, not detected in soil buried neat PLA, assessed that the inclusion of CP waste fibers inside PLA matrix, represented a valid route to promote a fast and easy PLA biodegradation if compared to the composting method commonly used, for which severe atmosphere conditions and specific microbial population are necessary.
Carbon fiber/ABS composites with different acrylonitrile, butadiene, and styrene components were produced via extrusion/injection and long fiber thermoplastic (LFT)/injection molding processes, respectively. The effect of the components on fiber length distribution, tensile, flexural, impact, and dynamic mechanical properties of the composites was investigated. The properties of carbon fiber/ABS composites produced using 12 mm‐long LFT pellets were markedly higher than those produced using extruded pellets made with 12 mm‐long chopped carbon fibers. Uses of LFT pellets were preferable to enhancing the mechanical properties of carbon fiber/ABS composites. The tensile, flexural, and dynamic mechanical properties were increased in order of ABS750sw > ABS720 ≥ ABS780 > ABS740, whereas the impact strength was increased in order of ABS740 > ABS780 > ABS720 ≈ ABS750sw. Less carbon fiber damages and less carbon fiber length degradation upon LFT processing resulted in longer fiber length distribution and higher fiber aspect ratio in the composites with LFT pellets, indicating a beneficial reinforcing effect, which was responsible for the increased mechanical properties of ABS composites, particularly with ABS750sw. The results were agreed with each other, significantly depending on the A, B, and S components, being supported by fiber length distribution, fiber aspect ratio, and fracture surfaces.
Polylactide (PLA), derived from bioresources, is an environmentally friendly plastic which has attracted tremendous interests in both academia and industry. This study investigates the feasibility of direct injection molding of PLA/wood‐fiber composites and their mechanical and longitudinal shrinkage behaviors under different molding conditions. To understand the processing–property relationship of the thermally sensitive composites, response surface methodology was applied to study the effects of molding parameters, as well as their interacting effects, on the tensile strength and the longitudinal shrinkage of the composites. Melt temperature, packing pressure, and injection speed were chosen as the molding parameters studied. The statistical models were validated through confirmation experiments. The predicted values are in agreement with experimental data, and the average prediction accuracy is more than 95% for both tensile strength and longitudinal shrinkage. The models would not only improve our understanding of the tensile strength and shrinkage behaviors, but also can be used to help tooling design and select a proper processing window to maximize the tensile strength while achieving the desired longitudinal shrinkage. Tensile Strength and Shrinkage Prediction
Extrusion processing and properties of fiber-reinforced polymer matrix composites may be influenced by the fiber feeding route upon extrusion. The purpose of the present study was to investigate the effect of fiber feeding route on the fiber length distribution, electromagnetic interference shielding effectiveness (EMI SE), tensile, and flexural properties and heat deflection temperature of resulting composites with different fiber contents. H–NiCF/polypropylene and S–NiCF/polypropylene pellets were produced through two different feeding routes of nickel-coated carbon fiber (NiCF), hopper feeding (H) and side feeding (S) upon extrusion process, respectively. NiCF-reinforced polypropylene (PP) composites were fabricated by means of compression molding using each pellet, respectively. The effect of fiber feeding route on the electromagnetic, mechanical, and thermal properties of the composites with various NiCF contents was studied. S–NiCF/PP composites exhibited the EMI SE, tensile, and flexural properties and heat deflection temperature higher than H–NiCF/PP composites. The improved properties of S–NiCF/PP composites were ascribed to higher aspect ratio and longer fiber distribution of NiCF remaining in the composite than H–NiCF/PP counterparts, due to less shearing and fiber damages during extrusion.
In this work, the rheological, mechanical and morphological properties of flax fiber polypropylene composites were investigated. The effect of incorporating a polypropylene grafted acrylic acid or a polypropylene grafted maleic anhydride on these properties has been studied as well. According to scanning electron microscopic observations and tensile tests, the addition of a compatibilizer improved the interfacial adhesion between the flax fibers and the polymer matrix. The tensile modulus of composite containing 30 wt% flax fibers was improved by 200 % and the tensile strength improved by 60 % in comparison with the neat PP. Plasticizing effect of the compatibilizers as a result of their lower melt flow index was also shown to decrease the rheological properties of the composites, even though the effect was not pronounced on the mechanical properties.
Polypropylene (PP) nanocomposites containing spray dried cellulose nanocrystals (CNC), freeze dried CNC, and spray freeze dried CNC (CNCSFD) were prepared via melt mixing in an internal batch mixer. Polarized light, scanning electron, and atomic force microscopy showed significantly better dispersion of CNCSFD in PP/CNC nanocomposites, compared to the spray dried and freeze dried CNC. Rheological measurements, including linear and non-linear viscoelastic tests were performed on PP/CNC samples. The results of microscopy were supported by small amplitude oscillatory (SAOS) tests, which showed substantial rise in the magnitudes of key rheological parameters of PP samples containing CNCSFD. Steady shear results revealed a strong shear thinning behavior of PP samples containing CNCSFD. Moreover, PP melts containing CNCSFD exhibited a yield stress. The magnitude of yield stress and degree of shear thinning behavior increased with CNCSFD concentration. It was found that CNCSFD agglomerates with web-like structure were more effective in modifying rheological properties. This effect was attributed to better dispersion of agglomerates with web-like structure. Dynamic mechanical analysis (DMA) showed considerable improvement in modulus of samples containing CNCSFD agglomerates. The percolation mechanical model, with modified volume percolation threshold and filler network strength values, and the Halpin-Kardos model were used to fit the experimental results.