界面改性增强塑木复合材料力学性能的研究进展

综述了国内外界面改性增强塑木复合材料力学性能的研究进展，包括界面改性增强的作用机理、木纤维的表面改性、塑料的表面改性和添加界面相容剂等，并展望了塑木复合材料界面改性研究的未来趋势。     

液晶高分子及其原位复合材料研究进展

综述了近年来液晶聚合物及其原位复合材料的研究进展，重点阐述了目前商品化的液晶共聚酯的性能及结构，热致液晶聚合物(TLCP)与热塑性工程塑料(TP)进行原位复合时TLCP微纤化形成的机理及流变学性能，从而探讨复合材料微观结构与力学性能的关系，聚合共混物的加工性能。另外，还介绍了液晶聚合物原位复合材料的界面相容性，不同的相容剂对共混物界面附着力的改善作用。     

生物质纤维填充聚合物复合材料的界面行为

将木粉和聚合物加入HAAKE流变仪中熔融共混制备了木粉/聚合物复合材料,对比不同木粉预处理方式(碱处理、酸处理)及相容剂改善木粉与聚合物界面相容性的效果。红外光谱(FT-IR)结果表明,碱处理木粉去除了木粉中的小分子物质,酸处理木粉使木粉表面被酯化。木粉碱处理提高了木粉/聚合物复合材料的力学性能,扫描电镜(SEM)照片表明预处理后木粉与聚合物间的相容性得到了改善。使用合适的相容剂也可以改善木粉与聚合物的相容性,提高复合材料的力学性能。同时相容剂和碱处理木粉及酸处理木粉存在协同效应。     

界面改性增强塑木复合材料力学性能的研究进展

综述了国内外界面改性增强塑木复合材料力学性能的研究进展,包括界面改性增强的作用机理、木纤维的表面改性、塑料的表面改性和添加界面相容剂等,并展望了塑木复合材料界面改性研究的未来趋势。     

不同相容剂对聚丙烯/甘蔗渣复合材料力学性能的影响

利用熔融接枝法制备了5种大分子相容剂,用于聚丙烯/甘蔗渣(PP/BF)复合材料,以改善甘蔗渣纤维与聚合物基体间的界面粘接。考察了相容剂种类与含量对PP/BF复合材料力学性能的影响。结果表明,相容剂在改善PP/BF复合材料的界面相容性上起到重要作用,在5种大分子相容剂中,PP-g-MAH对体系有较好的增强作用,而乙烯-辛烯无规共聚物接枝马来酸酐(POE-g-MAH)对体系的增韧效应显著。两种相容剂在其用量为10%时分别达到最佳改性效果,与未添加相容剂的复合材料相比,前者使PP/PP-g-MAH/BF复合材料的拉伸强度提高了16.6%,后者使PP/POE-g-MAH/BF复合材料的缺口冲击强度增加了640%。     

椰壳纤维/抗冲共聚聚丙烯复合材料的研究

采用SEM对椰壳纤维及其与抗冲共聚聚丙烯(IPC)的复合材料的亚微观形貌进行了研究.碱溶液能明显消除了纤维表面的角质表层.从纤维断面的形貌看出其横断面类似于蜂窝状,由大量的形状不一的孔洞组成,这是该纤维质轻的主要原因.添加相容剂的复合材料断面显示,椰壳纤维与IPC基体的界面黏结明显好于未加相容剂的复合材料.结果表明,随着相容剂含量及纤维含量的增加,复合材料的拉伸强度明显提高.同时还表现出,相容剂对提高高纤维含量复合材料的拉伸强度更为有效.此外,相容剂及椰壳纤维同样能明显提高该复合材料的弯曲强度.     

含柔性链大分子偶联剂对SF/PP木塑复合材料结构和性能的影响

合成含柔性链段的大分子偶联剂,以此作为剑麻纤维(SF)/聚丙烯(PP)木塑复合材料的界面相容剂,研究其对复合材料力学性能、热性能、晶态结构和微观结构的影响,提出复合材料界面增容的机理。实验结果表明,经含柔性链段大分子偶联剂表面处理SF后,复合材料的界面相容性得到显著改善,冲击强度可达22.08kJ/m2,比未经偶联剂处理的复合材料提高了49.4%;热稳定性和PP相的结晶速率及结晶度有所提高,晶态结构无变化,仍是典型的α晶型。     

刚性粒子填充聚合物的增强增韧与界面相结构

介绍了作者近年来在无机刚性粒子增强增韧聚合物（尼龙、聚丙烯、聚乙烯）方面的最新研究结果．实验表明，无机刚性粒子填充聚合物的增强增韧与界面相结构有着密切的关系。在保证无机刚性粒子均匀分散的条件下，界面相结构是决定性的因素，界面相容剂的性质、界面相互相作用的程度和界面层厚度可以调节和控制复事材料的最终力学性能。     

剑麻/聚丙烯复合材料的冲击性能及其预测

采用注塑工艺制备剑麻纤维增强聚丙烯复合材料,研究纤维含量、长度及其分布、不同基体树脂和相容剂类型等对复合材料冲击性能的影响。分析单纤维强度的分散性,采用修正的Weibull分布模型估算临界纤维强度,并对复合材料的冲击强度进行预测。结果表明：剑麻/聚丙烯的冲击强度随纤维含量增加而升高,树脂基体的性质对冲击强度具有显著的作用;界面层为刚性层的相容剂MAPP对冲击强度具有负作用,而界面层为柔性层的相容剂PP-g-GMA对冲击强度具有提高作用;同等含量下,使用PP-g-GMA后复合材料的冲击强度比使用MAPP提高21.7%。通过KH550硅烷溶液处理后的纤维与PP-g-GMA反应,在界面处引入更加柔性的界面层,使冲击强度比引入MAPP提高50.7%。将纤维取向因子引入冲击强度模型后,预测值与实测值符合较好。     

纤维增强热塑性片材的关键技术与成型工艺

热塑性复合材料以其优越性能以及便于回收,近年来其增长速率几乎是热固性复合材料的2倍。以玻纤毡为增强材料,热塑性树脂为基体制备的复合片材GMT(Class Mat Reinforced Thermoplastics)是最重要的品种。为适应我国轿车工业的发展,“纤维增强热塑性片材的关键技术与成型工艺”在1996年作为863新材料专题立项,经过4年多时间的艰苦努力,突破一系列关键技术,无活性基团的聚丙烯(有机物)与玻璃纤维(无机物)之间的界面结合;高粘熔融聚合物浸渍(多孔纤维层);加温、加压     

Morphology and properties of microfibrillar composites based on recycled poly (ethylene terephthalate) and high density polyethylene

Microfibrillar composites (MFCs) from recycled high density polyethylene (R-HDPE)/recycled poly (ethylene terephthalate) (R-PET) (75/25 w/w) were made through reactive extrusion and post-extrusion strand stretching. The resultant MFCs could be processed at HDPE processing temperature. The compatibility between microfibers and R-HDPE matrix was improved through compatibilizers. Of the three compatibilizers evaluated, ethylene glycidyl methacrylate copolymer (E–GMA) performed the best. The addition of compatibilizers did not obviously change the size of R-PET fibers in MFCs. The toughness of MFC was significantly enhanced, and R-PET phase did not crystallize when 5% E–GMA was used. The process of manufacturing MFCs provides a way to recycle commingled plastics, and MFCs would be potential matrices for natural fiber polymer composites.     

Effect of a novel coupling agent,alkyl ketene dimer,on the mechanical properties of wood–plastic composites

The objective of this study was to investigate the incorporation of poplar wood fibers both with and without a novel coupling agent, alkyl ketene dimer (AKD), on the mechanical properties of wood fiber/polypropylene (PP) composites. The resulting properties were compared to those obtained with the most commonly used coupling agent, maleic anhydride grafted PP (MAPP). Tensile and impact strengths of the composites decreased with increasing poplar wood fibers content. Tensile modulus of the composites increased by the incorporation of the wood fibers content up to 70 wt% but further increment in the wood fibers decreased the tensile modulus. At the constant content of poplar wood fibers (70 wt%), the tensile strength determined for the coupled composites with 5% AKD increased by 41% in comparison with the non-coupled composites while the tensile modulus increased by 45%, the impact strength of the coupled composites increased by 38%. The performance of 5% AKD on the mechanical properties of the composites is a little better than 3% MAPP. The good performance of 5% AKD is attributed to the enhanced compatibility between the poplar wood fibers and the polymer matrix. The increase in mechanical properties of the composites demonstrated that AKD is an effective coupling agent for wood fiber/PP composites.     

Wood-plastic composites based on HDPE and ionic liquid additives

The improvement of wood-plastic composites properties by additives and compatibilizers is a critical issue to produce value-added materials. High-density polyethylene-wood composites have been obtained through compression molding at 140 °C, using two types of additives, namely methyltrioctylammonium bis (trifluoromethylsulfonyl)imide and trihexyltetradecylphosphonium bis (2,4,4-trimethylpentyl) phosphinate room temperature ionic liquids. The ionic liquids improve the interfacial adhesion between the wood and the polymer phases, contributing to an increased stability of the material to water action and to an improved impact resistance and tensile strength in comparison with the reference. Also, the FTIR spectroscopy tests have proven a higher resistance of the ionic liquid-containing composites to accelerated photooxidation. Preliminary screening tests have also proven the antifungal character of the ionic liquids used in this study against brown rot (Postia placenta). This study opens new insights in the domain of polymeric composite materials, through documenting the possibility of blending new types of chemically distinct materials, difficult to be achieved by traditional functionalization/derivatization routes.     

Surface modification and adhesion mechanisms in woodfiber-polypropylene composites

The interfacial adhesion between wood fiber and thermoplastic matrix polymer plays an important role in determining the performance of wood-polymer composites. The objectives of this research were to elucidate the interaction between the anhydride groups of maleated polypropylene (MAPP) and hydroxyl groups of wood fiber, and to clarify the mechanisms responsible for the interfacial adhesion between wood fiber and polypropylene matrix. The modification techniques used were bulk treatment in a thermokinetic reactive processor and solution coating in xylene. FT-IR was used to identify the nature of bonds between wood fiber and MAPP. IGC and wood veneer pull-out test was used to estimate the interfacial adhesion. Mechanical properties of injection molded woodfiber-polypropylene composites were also determined and compared with the results of esterification reaction and interfacial adhesion tests. Confocal Microscopy was employed to observe the morphology at the wood fiber-polypropylene interface, and the dispersion and orientation of wood fiber in the polypropylene matrix, respectively. The effectiveness of MAPP to improve the mechanical properties (particularly the tensile strength) of the composites was attributed to the compatibilization effect which is accomplished by reducing the total wood fiber surface free energy, improving the polymer matrix impregnation, improving fiber dispersion, improving fiber orientation, and enhancing the interfacial adhesion through mechanical interlocking. There was no conclusive evidence of the effects of ester links on the mechanical properties of the composites.     

Effects of hemicellulose extraction on properties of wood flour and wood-plastic composites

Hygroscopicity, low durability, and low thermal resistance are disadvantages of lignocellulosic materials that also plague wood-plastic composites (WPCs). Hemicellulose is the most hydrophilic wood polymer and is currently considered as a sugar source for the bioethanol industry. The objective of this research is to extract hemicellulose from woody materials and enhance the properties of WPC by diminishing the hydrophilic character of wood. Hemicellulose of Southern Yellow Pine was extracted by hot-water at three different temperatures: 140, 155, and 170 °C. Wood flour was compounded with polypropylene in an extruder, both with and without a coupling agent. Injection molding was used to make tensile test samples. The thermal stability of wood flour was found to have increased after extraction. Extraction of hemicellulose improved the tensile strength and water resistance of composites, which may indicate a decrease in the hygroscopicity of wood flour, better compatibility, and interfacial bonding of the filler and matrix.     

Cellulose derived composites – A new method for materials processing

 This research demonstrated for the first time a method for producing net shape polymer, ceramic and carbon composites using wood as a precursor. The conversion of wood to carbon has been practiced for centuries but the controlled thermal decomposition to form a monolithic carbon to be used as a template for composites as demonstrated by this research is a unique discovery. This was accomplished by thermal decomposition of wood under controlled conditions to produce a crack-free porous carbon monolith which was readily shaped by conventional methods. The shaped carbons have converted to carbon/polymer composites, carbon/carbon composites, ceramics, and ceramic composites without significant changes in dimensions. This research has demonstrated that composites derived from wood can eliminate several expensive processing steps. Specifically, no fiber lay-up or powder consolidation is required, and final grinding and polishing steps are minimized.     

Fracture mechanisms of wood/polyester laminates under quasi-static compression and shear loading

There is increasing use of natural fiber/polymer composites as alternatives to traditional structural materials like concrete and metals and to the inorganic fibers like carbon. While the fracture mechanisms during crushing of synthetic fiber/polymer composites have been thoroughly studied, limited information is available on post-fracture investigation and identification of the dominant fracture mechanisms of wood/polyester composites. In this study laminates of Douglas-fir veneer were fabricated using a catalyzed polyester resin and their potentials as energy absorbers have been investigated and discussed. Factors for this study were (i) laminates symmetry (face layers of 0° or 90°), (ii) lay-up balance (balanced and unbalanced) and (iii) number of lamina (8, 11, and 12). Samples were tested under quasi-static Combined Loading Compression (CLC) and their compressive performances were compared to control specimens using glass fiber as reinforcement. Results indicated that the effect of symmetry on compressive properties of wood veneer/polyester laminates was significant with laminates with face layers of 90° and core layers of 0° had the highest deflection to failure. Increasing the wood/polyester laminate thickness enhanced their energy absorbing ability by bringing more fracture mechanisms into play but it noticeably reduced the laminates compressive modulus. Despite the brittle failure of glass fiber composites wood laminates exhibited a progressive fracture mechanisms with shear buckling as the dominant mode of failure in symmetric samples. This progressive failure with high energy absorbing ability make wood/polyester laminates a good candidate to be used as an energy absorber structure where high deflection to failure and longer failure time are required.     

Multiscale mechanical and structural characterizations of Palmetto wood for bio-inspired hierarchically structured polymer composites

There has been a great deal of effort focused on engineering polymer composites with hierarchical microstructures consisting of one or more ingredients that can be organized differently across multiple length scales. However, there are hierarchical microstructures that have evolved over eons in biological materials. These unique structure–property relationships may serve as templates for engineering hierarchically structured polymer composites with tailored properties. One such biological material is the Palmetto wood of South Carolina, which was successfully used as a protective structure during the Revolutionary and Civil Wars to absorb cannon shot. Through an assembly of microfibers into macrofibers embedded in a cellulose matrix, the Palmetto wood has optimized its ability to resist failure when subjected to extreme dynamic loading events, such as hurricanes. Understanding of the dynamic and static structure–property relationship in Palmetto wood can facilitate the development of new hierarchically structured polymer composites with increased resistance to failure. Therefore, the structure–property relationship in Palmetto wood has been studied using novel multiscale microstructural and mechanical characterization techniques. Models have been developed that indicate that the hierarchical structure of Palmetto wood obeys the linear Rule-of-Mixtures across multiple length scales. This understanding has led to the development of new polymer composite structures that exhibit properties similar to Palmetto wood using conventional laminated carbon fiber–epoxy composites and new polymer nanocomposites consisting of carbon nanofibers. The use of the nanofibers appears to enhance the interaction between the composite components in a manner similar to the interaction between fibers in the Palmetto wood that enables the laminated composite to behave more like the individual layers by resisting the tendency to delaminate and increasing the Weibull statistical parameters closer to those observed in Palmetto wood.