The effect of silane treated- and untreated-talc on the mechanical and physico-mechanical properties of poly(lactic acid)/newspaper fibers/talc hybrid composites

This paper evaluates the effect of the addition of silane treated- and untreated- talc as the fillers on the mechanical and physico-mechanical properties of poly(lactic acid) (PLA)/recycled newspaper cellulose fibers (RNCF)/talc hybrid composites. For this purpose, 10 wt% of a talc with and without silane treatment were incorporated into PLA/RNCF (60 wt%/30 wt%) composites that were processed by a micro-compounding and molding system. PLA is utilized is a bio-based polymer that made from dextrose, a derivative of corn. Talc is also a natural product. The RNCF and talc hybrid reinforcements of PLA polymer matrix were targeted to design and engineer bio-based composites of balanced properties with added advantages of cost benefits besides the eco-friendliness of all the components in the composites. In this work, the flexural and impact properties of PLA/RNCF composites improved significantly with the addition of 10 wt% talc. The flexural and impact strength of these hybrid composites were found to be significantly higher than that made from either PLA/RNCF. The hybrid composites showed improved properties such as flexural strength of 132 MPa and flexural modulus of 15.3 GPa, while the unhybridized PLA/RNCF based composites exhibited flexural strength and modulus values of 77 MPa and 6.7 GPa, respectively. The DMA storage modulus and the loss modulus of the PLA/RNCF hybrid composites were found to increase, whereas the mechanical loss factor (tan delta) was found to decrease. The storage modulus increased with the addition of talc, because the talc generated a stiffer interface in the polymer matrix. Differential scanning calorimetry (DSC) thermograms of neat PLA and of the hybrid composites showed nearly the similar glass transition temperatures and melting temperatures. Scanning electron microscopy (SEM) micrographs of the fracture surface of Notched Izod impact specimen of 10 wt% talc filled PLA/RNCF composite showed well filler particle dispersion in the matrix and no large aggregates are present. The comparison data of mechanical properties among samples filled with silane-treated- and untreated- talc fillers showed that the hybrid composites filled with silane treated talc displayed the better mechanical prosperities relative to the other hybrid composites. Talc-filled RNCF-reinforced polypropylene (PP) hybrid composites were also made in the same way that of PLA hybrid composites for a comparison. The PLA hybrid bio-based composites showed much improvement in mechanical properties as compared to PP-based hybrid counterparts. This suggests that these PLA hybrid bio-based composites have a potential to replace glass fibers in many applications that do not require very high load bearing capabilities and these recycled newspaper cellulose fibers could be a good candidate reinforcement fiber of high performance hybrid biocomposites.     

Morphology, dynamic mechanical and thermal studies on poly(styrene-co-acrylonitrile) modified epoxy resin/glass fibre composites

Poly(styrene-co-acrylonitrile) (SAN) was used to modify diglycidyl ether of bisphenol-A (DGEBA) type epoxy resin cured with diamino diphenyl sulfone (DDS) and the modified epoxy resin was used as the matrix for fibre reinforced composites (FRPs) in order to get improved mechanical and thermal properties. E-glass fibre was used as the fibre reinforcement. The morphology, dynamic mechanical and thermal characteristics of the systems were analyzed. Morphological analysis revealed heterogeneous dispersed morphology. There was good adhesion between the matrix polymer and the glass fibre. The dynamic moduli, mechanical loss and damping behaviour as a function of temperature of the systems were studied using dynamic mechanical analysis (DMA). DMA studies showed that DDS cured epoxy resin/SAN/glass fibre composite systems have two T_gs corresponding to epoxy rich and SAN rich phases. The effect of thermoplastic modification and fibre loading on the dynamic mechanical properties of the composites were also analyzed. Thermogravimetric analysis (TGA) revealed the superior thermal stability of composite system.     

Mechanical and thermal properties of chicken feather fiber/PLA green composites

Chicken feather fiber (CFF)/reinforced poly(lactic acid) (PLA) composites were processed using a twin-screw extruder and an injection molder. The tensile moduli of CFF/PLA composites with different CFF content (2, 5, 8 and 10 wt%) were found to be higher than that of pure PLA, and a maximum value of 4.2 GPa (16%↑) was attained with 5 wt% of CFF without causing any substantial weight increment. The morphology, evaluated by scanning electron microscopy (SEM), indicated that an uniform dispersion of CFF in the PLA matrix existed. The mechanical and thermal properties of pure PLA and CFF/PLA composites were compared using dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and thermogravimetric analysis (TGA). DMA results revealed that the storage modulus of the composites increased with respect to the pure polymer, whereas the mechanical loss factor (tan δ) decreased. The results of TGA experiments indicated that the addition of CFF enhanced the thermal stability of the composites as compared to pure PLA. The outcome obtained from this study is believed to assist the development of environmentally-friendly composites from biodegradable polymers, especially for converting agricultural waste – chicken feather into useful products.     

Fabrication and characterization of fully biodegradable natural fiber-reinforced poly(lactic acid) composites

Polymer composites were fabricated with poly(lactic acid) (PLA) and cellulosic natural fibers combining the wet-laid fiber sheet forming method with the film stacking composite-making process. The natural fibers studied included hardwood high yield pulp, softwood high yield pulp, and bleached kraft softwood pulp fibers. Composite mechanical and thermal properties were characterized. The incorporation of pulp fibers significantly increased the composite storage moduli and elasticity, promoted the cold crystallization and recrystallization of PLA, and dramatically improved composite tensile moduli and strengths. The highest composite tensile strength achieved was 121 MPa, nearly one fold higher than that of the neat PLA. The overall fiber efficiency factors for composite tensile strengths derived from the micromechanics models were found to be much higher than that of conventional random short fiber-reinforced composites, suggesting the fiber–fiber bond also positively contributed to the composites’ strengths.     

Effect of fiber surface treatments on mechanical and abrasive wear performance of polylactide/jute composites

The main focus of this work is to improve the adhesion of jute fiber with polylactide (PLA). For this purpose, surface of the jute fiber was modified by alkali, permanganate, peroxide and silane treatments. The surface modified fibers were characterized by FTIR spectroscopy. Unidirectional composites were prepared with treated jute fibers and PLA matrix by hot pressing of solvent impregnated prepregs. Surface treatments resulted in enhancement of tensile and flexural properties and reduction in Izod impact strength. Dynamic mechanical analysis (DMA) results showed that, treated composites have higher storage modulus and lower tangent delta with respect to untreated composite. The degree of interfacial adhesion between the jute fiber and PLA was estimated using adhesion parameter obtained through DMA data. The results of thermogravimetric analysis (TGA) showed a higher thermal stability for silane treated composites. Experimental results on abrasive wear tests revealed that the wear resistance of composite is sensitive to fiber/matrix adhesion.     

聚丙烯/热致液晶聚合物/玻璃纤维混杂复合材料 Ⅱ: 混杂复合材料的静态及动态力学性能

对具有良好液晶聚合物微纤结构的聚丙烯/热致液晶聚合物/玻璃纤维 (PP/TLCP/GF) 混杂复合材料,使用静态拉伸和动态力学分析 (DMA) 的方法研究了材料的力学性能。拉伸实验结果表明,混杂复合材料的拉伸强度和模量随着PP和TLCP挤出后的牵伸速率增大而上升,并且含有增容剂PP-g-MAH的体系,力学性能更优异。DMA测试结果表明,混杂复合材料的动态模量E'随着体系中玻纤的含量增加而增大;当体系中加入增容剂后,复合材料的刚性得到进一步提高。但无论是否使用了增容剂PP-g-MAH,当体系中玻纤含量高于20%后,模量随玻纤含量增大的趋势变缓。当体系中增强相的含量增加,以及加入增容剂使增强相与基体的界面粘结得到改善后,PP基体的损耗因子 (tanδ) 峰值都有一定的减小。      

Effect of fiber surface-treatments on the properties of poly(lactic acid)/ramie composites

Ramie fiber reinforced poly(lactic acid) (PLA) composites were prepared by a two-roll mill. Ramie was treated by alkali and silane (3-aminopropyltriethoxy silane and γ-glycidoxypropyltrimethoxy silane). Effect of surface treatment on the properties of the composites was studied. The tensile, flexural and impact strength of the composites have a significant improvement. Dynamic mechanical analysis (DMA) results show that the storage moduli of the composites with treated ramie increase with respect to the plain PLA and the composites with untreated fiber whereas tangent delta decreases. The Vicat softening temperature of the composites with treated fiber is greatly higher than that of the composites with untreated fiber. The results of thermogravimetric analysis (TGA) show that fiber treatment can improve the degradation temperature of the composites. Moreover, the morphology of fracture surface evaluated by scanning electron microscopy (SEM) indicates that surface treatment can get better adhesion between the fiber and the matrix.     

“Green” composites from recycled cellulose and poly(lactic acid): Physico-mechanical and morphological properties evaluation

“Green”/biobased composites were prepared from poly(lactic acid) (PLA) and recycled cellulose fibers (from newsprint) by extrusion followed by injection molding processing. The physico-mechanical and morphological properties of the composites were investigated as a function of varying amounts of cellulose fibers. Compared to the neat resin, the tensile and flexural moduli of the composites were significantly higher. This is due to higher modulus of the reinforcement added to the PLA matrix. Dynamic mechanical analysis (DMA) results also confirmed that the storage modulus of PLA increased on reinforcements with cellulose fibers indicating the stress transfers from the matrix resin to cellulose fiber. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the presence of cellulose fibers did not significantly affect the crystallinity, or the thermal decomposition of PLA matrix up to 30 wt% cellulose fiber content. Overall it was concluded that recycled cellulose fibers from newsprint could be a potential reinforcement for the high performance biodegradable polymer composites.     

相容剂对长玻纤增强热塑性聚氨酯弹性体/聚乳酸复合材料性能的影响

采用熔体浸渍工艺制备长玻纤增强热塑性聚氨酯弹性体(TPU)/聚乳酸(PLA)复合材料;以苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯(SAG)作为相容剂,热塑性弹性体聚氨酯作为增韧剂,聚乳酸为基体树脂,考察苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯用量对长玻璃纤维增强聚TPU/PLA复合材料性能的影响。结果表明,加入苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯能改善长玻璃纤维增强聚TPU/PLA复合材料的相容性;长玻璃纤维增强聚TPU/PLA复合材料的拉伸强度、缺口冲击强度、弯曲强度和模量等力学性能及储能模量随着苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯用量的增加呈先增加后降低的趋势,而长玻璃纤维增强聚TPU/PLA复合材料的损耗因子则随苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯含量的增加呈现降低后增加的趋势;通过复合材料的形态分析表明,加入相容剂的复合材料中玻璃纤维与基体树脂界面强度增加,且玻璃纤维表面有一层包覆的树脂基体;通过分析得出,当相容剂添加量为6%时,长玻璃纤维增强聚TPU/PLA复合材料的拉伸强度、弯曲强度和模量、缺口冲击强度等力学性能最优。     

偶联剂对玻璃纤维增强淀粉/聚乳酸复合材料性能的影响

分别以马来酸酐、KH550、KH560和KH570为偶联剂对玻璃纤维进行预处理,再与淀粉、聚乳酸(PLA)复合,通过熔融挤出法制备玻璃纤维增强淀粉/PLA复合材料。研究了偶联剂种类对玻璃纤维增强复合材料熔融指数、力学性能、热性能和熔融流变性能的影响。实验发现马来酸酐、KH550、KH570、KH560处理玻璃纤维增强淀粉/PLA复合材料的熔融指数和力学性能都依次增大,表明KH560处理玻璃纤维增强淀粉/PLA复合材料的界面黏结作用最强。对热性能进行表征发现,马来酸酐、KH550、KH570、KH560处理玻璃纤维增强淀粉/PLA复合材料玻璃化转变温度、重结晶温度、结晶度和热稳定性均依次提高。受玻璃纤维与淀粉/PLA基体界面黏结效果的影响,马来酸酐、KH550、KH570、KH560处理玻璃纤维增强淀粉/PLA体系的储能模量和复数黏度依次增大。     

Kenaf natural fiber reinforced polypropylene composites: A discussion on manufacturing problems and solutions

As industry attempts to lessen the dependence on petroleum based fuels and products there is an increasing need to investigate more environmentally friendly, sustainable materials to replace existing materials. This study focused on the fabrication of kenaf fiber reinforced polypropylene sheets that could be thermoformed for a wide variety of applications with properties that are comparable to existing synthetic composites. The research done in this study has proven the ability to successfully fabricate kenaf–polypropylene natural fiber composites into sheet form. The optimal fabrication method for these materials was determined to be a compression molding process utilizing a layered sifting of a microfine polypropylene powder and chopped kenaf fibers. A fiber content of both 30% and 40% by weight has been proven to provide adequate reinforcement to increase the strength of the polypropylene powder. The use of a coupling agent, 3% Epolene enabled successful fiber–matrix adhesion. The kenaf–PP composites compression molded in this study proved to have superior tensile and flexural strength when compared to other compression molded natural fiber composites such as other kenaf, sisal, and coir reinforced thermoplastics. With the elastic modulus data from testing, it was also possible to compare the economic benefits of using this kenaf composite over other natural fibers and E-glass. The kenaf–maleated polypropylene composites manufactured in this study have a higher Modulus/Cost and a higher specific modulus than sisal, coir, and even E-glass thereby providing an opportunity for replacing existing materials with a higher strength, lower cost alternative that is environmentally friendly.     

Influence of short bamboo/glass fiber on the thermal, dynamic mechanical and rheological properties of polypropylene hybrid composites

The present article summarizes the development of polypropylene-bamboo/glass fiber reinforced hybrid composites (BGRP) using an intermeshing counter rotating twin screw extruder followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to improve the interfacial interaction between the fibers and matrix. The crystallization and melting behavior were investigated employing differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) indicates an increase in thermal stability of the matrix polymer with incorporation of bamboo and glass fibers, confirming the effect of hybridization and efficient fiber matrix interfacial adhesion. The dynamic mechanical analysis (DMA) showed an increase in storage modulus (E′) indicating higher stiffness in case of hybrid composites as compared with untreated composites and virgin matrix. The rheological behavior of the hybrid composites has also been studied using time–temperature superposition (TTS) principle and corresponding viscoelastic master curves have been constructed.     

改性椰纤维增强聚乳酸复合材料力学性能

目的添加适量椰纤维(CF)改善聚乳酸(PLA)的力学性能,以适应产品的包装。方法采用熔融共混法制备不同CF含量的CF/PLA复合材料。通过力学性能测试、扫描电子显微镜观察和动态热力学性能测试,探讨添加不同含量的碱洗CF对复合材料力学性能的影响。结果与纯PLA相比,复合材料的拉伸强度降低,冲击强度增大,储能模量增大,玻璃化转变温度降低。当碱洗CF质量分数为3%时,复合材料的冲击强度比纯PLA增加了24%。结论添加CF有利于提高复合材料的力学性能,碱液浸泡更有利于改善CF和PLA基体的界面相容性。     

粘胶纤维与Lyocell纤维增强聚乳酸复合材料的性能比较

以聚乳酸(PLA)为基体,分别采用粘胶纤维与Lyocell纤维这2种典型的再生纤维素纤维为增强纤维,通过熔融共混和注塑成型制备了再生纤维素纤维/PLA复合材料,并对这2种复合材料的性能进行了比较研究。结果表明,采用粘胶纤维或Lyocell纤维增强均可有效提高PLA复合材料的结晶度、力学性能和维卡软化温度。粘胶纤维的锯齿形截面有利于其与PLA基体的结合,因此粘胶纤维/PLA复合材料具有略高的冲击强度及拉伸强度。Lyocell纤维增强更有利于复合材料结晶度的提高,使得Lyocell/PLA复合材料具有更高的弹性模量和维卡软化温度。     

考虑纤维方向分布的玻纤增强PP复合材料拉伸性能

纤维方向及其分布对玻纤增强PP复合材料的力学特性具有至为关键的影响。提出了一种快速获取纤维数量及每根纤维方向的方法。通过引入方向张量, 利用Moldflow软件进行玻纤增强PP树脂注塑成型模拟获得纤维方向的平均分布, 结合显微方法观察判断特定点的纤维沿厚度方向的分层情况及定量判断纤维方向的分布。对轿车玻璃纤维增强注塑仪表板的纤维方向相对一致处取与纤维方向呈0°、45°、90°的样条, 通过拉伸实验测得拉伸模量, 利用所提出的方法研究了仪表板内玻纤方向的分布及其对拉伸模量的影响。研究结果表明: 玻纤增强注塑仪表板的力学性能是各向异性的, 其沿厚度方向纤维按方向大致可分为三层。     

Preparation,characterization and mechanical properties of the polylactide/perlite and the polylactide/montmorillonite composites

In this study polylactide (PLA)/perlite and PLA/montmorillonite (MMT) composites were prepared by melt extrusion and solvent dissolution methods. The effects of organic/inorganic ratios and the kind of inorganic compounds on the characterization of the composite materials were investigated. The thermal stability of the organic–inorganic composite materials was evaluated by TGA and DSC, and the morphology of these composites was measured as SEM images. The modulus of elasticity was evaluated by Dynamic mechanical analysis (DMA). The PLA/inorganic composites exhibited remarkable improvement of mechanical and thermal properties when compared with those of the pure PLA.     

Studies on mechanical,thermal and dynamic mechanical properties of untreated (raw) and treated coconut sheath fiber reinforced epoxy composites

The untreated (raw) coconut sheath fiber reinforced epoxy (UTCSE) composite and treated coconut sheath fiber reinforced epoxy (TCSE) composite have been fabricated using hand layup followed by compression molding technique. The prepared specimens were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques. The prepared specimens are cut as per ASTM Standards to measure tensile, flexural and impact strengths by using universal testing machine and izod impact tester respectively. The treated coconut sheath fiber reinforced epoxy composite (TCSE) posses higher mechanical strength and thermal stability compared to untreated (raw) coconut sheath fiber reinforced epoxy composite (UTCSE). In the SEM fracture analysis, TCSE composite showed better fiber–matrix bonding and absence of voids compared to UTCSE composite.     

纳米CaCO_3/PET短纤维/聚丙烯复合材料的制备及性能

制备了纳米CaCO3/聚丙烯、聚对苯二甲酸乙二酯(PET)短纤维/聚丙烯、CaCO3/PET短纤维/聚丙烯复合材料。分别测试了复合材料的力学性能,结果发现,与纳米CaCO3/聚丙烯、PET短纤维/聚丙烯两相复合材料相比,三相复合材料的力学性能尤其是冲击性能有明显的提高。采用X射线衍射(XRD)、动态力学分析(DMA)、电子扫描(SEM)系统研究了复合材料的增强机理,结果发现,在三相复合材料中,纳米CaCO3的加入明显提高了PET短纤维与聚丙烯基体界面之间的作用力和相容性,同时纳米CaCO3与PET短纤维的协同效应诱导了聚丙烯β晶的生成。     

竹纤维组合形态对竹纤维/聚丙烯复合材料性能的影响

以聚丙烯（PP）为基体,单根竹纤维（SBF）和竹纤维束（BFS）两种形态竹纤维为增强体,采用无纺气流铺装-模压工艺制备了SBF-BFS/PP复合材料。通过力学试验机、SEM、TGA、DSC等对SBF-BFS/PP复合材料的力学性能、微观形貌、热性能等进行表征,研究竹纤维形态配比变化对SBF-BFS/PP复合材料综合性能的影响。结果表明,在纤维总含量不变情况下,SBF在两种形态竹纤维中的含量逐步增加时,SBF-BFS/PP复合材料冲击强度和弹性模量逐步增加; SBF在两种形态竹纤维中质量分数为90wt%时,SBF-BFS/PP复合材料冲击强度和弹性模量比SBF质量分数为10wt%时分别提高了26.46%和38.39%; SEM结果表明,竹纤维与PP基体存在较差界面相容性,竹纤维出现断裂和拔出等现象;热失重结果表明,随着SBF含量的增加,SBF-BFS/PP复合材料的耐热性能并没有明显变化。此外,对SBF-BFS/PP复合材料的耐水性能测试结果表明,由于SBF比表面积大,随SBF含量的增加,SBF-BFS/PP复合材料中易吸水组分增加,从而导致其耐水性能下降。      

Analysis of effective elastic modulus for multiphased hybrid composites

Short fiber reinforced composites inherently have fiber length distribution (FLD) and fiber orientation distribution (FOD), which are important factors in determining mechanical properties of the composites. Since the internal structure has a direct effect on the mechanical properties of the composites, a Micro-CT was used to observe the three dimensional structure of fibers in the composites and to acquire FLD and FOD. It was successful to investigate FLD, FOD, and fiber orientation states and to predict the elastic modulus of the hybrid system. Since hybrid composites used in this study consist of three phases of particles, glass fibers, and matrix, theoretical hybrid modeling is required to consider reinforcing effects of both particles and glass fibers. Interaction between the particles and matrix was considered by using a perturbed stress–strain theory, the Tandon–Weng model. In addition, the laminating analogy approach (LAA) was used to predict the overall elastic modulus of the composite. Theoretical prediction of hybrid moduli indicated that there was a possibility of poor adhesion between glass fibers and matrix. The poor interfacial adhesion was confirmed by morphological experiments. This theoretical and experimental platform is expected to provide more insightful understanding on any kinds of multiphased hybrid composites.