改性剂对木塑复合材料力学性能影响的研究

采用木材纤维,分别与PE、PS、ABS、SAN等热塑性高分子聚合物,经热压复合工艺制成木塑复合板材,通过加入不同的改性剂以及改变改性剂的加入量,研究它们对木塑复合材料力学性能的影响。结果表明:改性剂的加入能使木材纤维与各种热塑性高分子聚合物很好地胶接;改性剂不同对木塑复合材料的性能产生不同的影响;改性剂的加入量为木材纤维用量的5%时,该法制作的木塑复合板材力学性能最佳。     

木塑复合工艺因子对复合材料性能的影响

选用2种人工林木材(马尾松与杨木)和3种废弃塑料(聚乙烯、聚丙烯及聚苯乙烯)为原料,采用木材与塑料冷混-热压工艺,通过正交试验研究不同树种、木材组元形态、补强剂、塑料种类、板材密度及不同木塑混合比等复合工艺因子对木塑复合材料性能的影响.结果表明树种、木材组元形态、塑料种类、木塑复合比例、板材密度与补强剂等复合工艺因子对木塑复合材料性能有不同程度的影响;提高塑料在木塑复合材料中的比例也可以达到与添加酚醛补强剂同样或更好的结果;以杨木原料、细长刨花形态、聚丙烯塑料、板材密度为1g*cm-3等为最佳复合工艺因子,制成的复合材料性能达到或超过相关普通刨花板,包括室外结构用刨花板性能指标.     

Effect of chemical modification on the properties of wood/polypropylene composites

对以铝酸酯为偶联剂对木粉进行表面改性处理后制备的木粉/聚丙烯复合材料的力学性能和形态学特征进行了研究。结果表明:铝酸酯偶联剂可以增加木塑复合材料的抗冲击强度,但会对复合材料的抗拉强度和抗弯强度造成负面的影响。对木塑复合材料的动态力学性能和微分扫描热量分析研究表明,以铝酸酯作为偶联剂,对木塑复合材料的储存模量和损失模量有少许增加,同时可降低材料的熔点和熔解热。利用扫描电镜观察木塑复合材料的木材与塑料界面发现,经铝酸酯处理过的木材与聚丙烯复合界面之间具有更好的相容性。这些研究结果表明,在木塑复合材料制造过程中利用廉价的铝酸酯作为木材化学改性剂,对改善复合材料的性质同样起作良好的作用。图6 表2 参16。     

聚丙烯比例对木塑复合材料性能的影响

通过正交试验,以木材纤维和废旧聚丙烯塑料为原料,异氰酸酯或马来酸酐作偶联剂,压制木材纤维/聚丙烯复合材料,研究聚丙烯(简称PP)用量对木塑复合材料性能的影响。结果表明,聚丙烯比例对复合材料的内结合强度、吸水厚度膨胀率、静曲强度和弹性模量有不同的影响。在热压时间、热压温度、复合材料密度相同的条件下,用异氰酸酯(简称MDI)作偶联剂,聚丙烯用量40%时复合材料的性能最佳;而用马来酸酐(简称MA)作偶联剂,聚丙烯用量50%时复合材料的性能最佳。     

聚丙烯比例对木塑复合材料性能的影响

以木材纤维和废旧聚丙烯塑料为原料,异氰酸酯(MDI)或马来酸酐(MA)为偶联剂,压制木材纤维/聚丙烯复合材料;通过正交试验,研究聚丙烯(PP)用量对木塑复合材料性能的影响.结果表明:PP比例对复合材料的内结合强度、吸水厚度膨胀率、静曲强度和弹性模量有不同程度的影响.在热压时间、热压温度、复合材料密度相同的条件下,在用MDI做偶联剂,PP用量为40%时,复合材料的性能最佳;在用MA做偶联剂,PP用量为50%时,复合材料的性能最佳.     

再生聚丙烯/木粉复合材料性能研究

研究木粉用量、PP-g-MAH相容剂、WBG晶型改性剂，对再生聚丙烯／未粉复合材料性能和结构形态的影响。试验结果表明：PP-g-MAH能增加木塑复合材料的相容性，提高木塑复合材料的性能；适量木粉能提高复合材料的拉伸模量、弯曲性能和热变彤温度，但材料的冲击强度和断裂伸长率有所降低。添加WBG晶型改性剂，能改善复合材料的晶体结构，提高材料的塑性。     

纤维增强木塑复合材料研究进展

木塑复合材料属于生物质复合材料的范畴,是一种无毒、可循环利用的环境友好型材料,从20世纪末开始到现在经历了20多年的高速产业化发展。但木塑复合材料力学性能偏低,特别是韧性差,导致应用领域偏窄,是目前制约木塑复合材料发展的主要因素之一。众多研究表明,将纤维添加到木塑复合材料中形成多元结构复合材料,可提高木塑复合材料的力学性能。本文概述了纤维增强木塑复合材料的研究现状,按天然纤维素纤维、合成纤维、非金属纤维、金属纤维4大类归纳了常用作增强复合材料的纤维,综述了采用玻璃纤维、矿物质纤维、碳纤维、芳纶纤维、聚对苯二甲酸乙二醇酯纤维和天然纤维素纤维等增强木塑复合材料的制备方法和增强效果。结果表明,不同种类的纤维对木塑复合材料均有不同程度的增强或增韧作用。短切纤维在添加量上存在"临界值",在"临界值"之前,添加量与增强效果呈正相关,在"临界值"之后呈负相关。连续玻璃纤维的增强效果尤为明显,其中冲击强度可增加20倍。天然纤维素纤维在木塑复合材料中的应用虽然较少,但目前在欧洲已被用于高附加值的汽车零部件领域。本文还介绍了银纹剪切带机制、刚性粒子增强理论、多缝开裂理论和复合力学理论等用于解释纤维增强复合材料的作用机制,这些理论均被用于解释纤维对于木塑复合材料基体的作用效果,其中后2种理论最常用于解释纤维对于复合材料强度提高的作用机制。本文同时指出,目前尚没有哪一种理论能全面揭示由于纤维加入后结构趋于复杂的木塑复合材料的力学行为。总结了纤维的添加对材料力学性能、吸湿性和热性能的影响,发现纤维的添加不仅可以提高木塑复合材料的力学强度,对于降低吸湿性和提高热稳定性也有积极效果,一些纤维的添加还可以提高基体的结晶度。本文最后提出纤维增强木塑复合材料产业化发展前景和需要解决的问题,包括进一步提高生产效率,研制纤维增强木塑复合材料专用装备,开发连续纤维增强木塑复合材料技术和开拓高性能、高附加值木塑复合材料市场。     

改善木塑复合材料性能的方法讨论

木塑复合材料是一种新型结构用材,目前已经大量应用于建筑装饰以及汽车、飞机制造等行业,是一种性能较为稳定的建设材料,但是在木塑复合材料的生产过程中由于其粘合性能的好坏直接影响着木塑复合材的强度,本文通过对木材或塑料等高分子基材进行相应处理方法的讨论,提出了提高木塑复合材性能的方法与途径。     

木材纤维与回收聚丙烯的热压复合工艺研究

研究了热压时间、热压温度、聚丙烯和偶联剂加入量等工艺因子对木材纤维和回收聚丙烯复合材料性能的影响。确定了压制密度为0．80g／cm3、10mm厚的木塑复合材料的最佳工艺条件为:热压温度175℃、热压时间8min、塑料加入量40％、偶联剂的加入量4％。在此条件下压制的木塑复合板材,物理力学性能中的内结合强度和吸水厚度膨胀率与中密度板的国家标准相比达到优等水平,静曲强度和弹性模量基本满足中密度板的国家标准要求。     

浅论木塑新材料对机械设备的要求

介绍了木塑复合材料（WPC）的特点及其加工工艺,探讨木塑复合材料生产与木材加工、塑料加工对机械设备的不同要求。     

Effect of Wood Variables on the Properties of Wood Fiber-Polypropylene Composites

The effect of wood species (Chinese fir and Poplar), wood fiber content (10%, 25%, 40%) and wood fiber sizes (16 to 32 mesh, 32-65 mesh, above 65 mesh) on the properties of the wood fiber-Polypropylene composites were studied in this paper. The results indicate that the effect of wood fiber content and size in composite were more important than that of chosen wood species. Compared with polypropylene without wood fiber, the flexural strength of the composites increased when adding wood fiber into polypropylene, but the tensile and unnotched charpy impact strength decreased. And the above strength decreased with the wood fiber content increasing. When the wood fiber size becoming smaller (in higher mesh), the strength increased. In the comparison of wood species, the properties of composite using Chinese fir wood were better than that of Poplar, but not significant. The dynamic mechanical properties of the composites and PP were also tested and analyzed in this paper.     

Effect of the amount of lignin on tensile properties of single wood fibers

Chemical components are the main factors affecting the mechanical properties of wood fibers. Lignin is one of the main components of wood cell walls and has a critical effect on the mechanical properties of paper pulp and wood fiber based composites. In this study, we carried out tensile tests on single mature latewood tracheids of Chinese fir (Cunninghamia lanciolata (Lamb.) Hook.), using three different delignified treatment methods to obtain different amounts of lignin. We applied single fiber tests to study the effect of the amount of lignin on mechanical tensile properties of single wood fibers at the cellular level. The results show that in their dry state, the modulus of elasticity of single fibers decreased with the reduction in the amount of lignin; even their absolute values were not high. The amount of lignin affects the tensile strength and elongation of single fibers considerably. Tensile strength and elongation of single fibers increase with a reduction in the amount of lignin.     

纳米CaCO3对木纤维增强生物可降解复合材料力学性能的影响

为探索纳米CaCO₃对增强生物可降解复合材料力学性能的影响,采用混炼、注射成型工艺制备纳米CaCO₃改性木纤维/聚乳酸复合材料,研究了纳米粒子添加量（1wt%,2wt%,3wt%,4wt%）及粒子预处理（偶联剂,硬脂酸,偶联剂-硬脂酸）对材料拉伸性能与冲击性能的影响。随着CaCO₃添加量增加,复合材料力学强度先增大后减小,质量分数2%时材料拉伸强度和冲击强度分别提高8%与20%,粒子的增韧效果明显。预处理不仅能增强木纤维与聚乳酸的结合,也提高了纳米粒子分散性,增强材料整体力学性能。纳米粒子在聚合物基体中的分散性及其与聚合物界面结合是影响材料性能的关键。     

木纤维PP/PE共混物复合材料的流变和力学性能(英文)

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.     

Improved interaction between wood and synthetic polymers in wood/polymer composites

Summary This article describes the properties of wood polymer composites consisting of linear low density polyethylene (LLDPE) and wood flour (WF). In an attempt to improve the interfacial adhesion between the matrix and the filler, different compatibilizers were used. The interaction between polymer and wood were studied by comparing LLDPE/WF composites with composites when compatibilizer was added. The experimental measurements were conducted by impact and tensile strength testing and Scanning Electron Microscopy (SEM). The mechanical properties of the composites were improved with SEBS triblock copolymer modified with maleic anhydride and with the ionomer polymer, Surlyn, as compatibilizers. SEM fractography confirmed better adhesion between wood particles and LLDPE matrix when SEBS was present.This study was financed by the Swedish National Board for Industrial and Technical Development (NUTEK) which is gratefully acknowledged     

Performance of thermomechanical wood fibers in polypropylene composites

ABSTRACT

Thermomechanical wood fibers, as usually used for medium density fiberboard or cardboard production, feature promising characteristics, like a high aspect ratio, for the utilization in thermoplastic composites. The present study investigates the influence of fiber loading and fiber geometry on the mechanical properties of wood-polypropylene composites in order to confirm the results that were found in a previously published literature review. Composites were compounded at fiber contents from 20 to 60 wt.%, using a co-rotating twin-screw extruder and subsequently injection molded to test specimens. Field emission scanning electron microscopy was carried out to evaluate the fracture morphology of the composites. Fiber length was evaluated using an applying a dynamic image analysis system. Compounding reduced fiber lengths up to 97%. The mechanical properties decreased with increasing fiber content for composites without a coupling agent. Strength properties peaking at a fiber content of 50?wt.% for composites containing MAPP. Tensile strength and flexural strength reached 48.1 and 76.4 MPa, respectively. However, it was found that the processing of these fibers into conventional compounding equipment is still challenging.     

Effects of impregnation and heat treatment on the physical and mechanical properties of Scots pine (Pinus sylvestris) wood

Wood modification, of which thermal modification is one of the best-known methods, offers possible improvement in wood properties without imposing undue strain on the environment. This study investigates improvement of the properties of heat-treated solid wood. Scots pine (Pinus sylvestris) was modified in two stages: impregnation with modifiers followed by heat treatment at different temperatures. The impregnation was done with water glass, melamine, silicone, and tall oil. The heat treatment was performed at the temperatures of 180°C and 212°C for three hours. The modified samples were analyzed using performance indicators and scanning electron microscope micrographs. The mechanical and physical properties were determined with water absorption, swelling, bending strength, and impact strength tests. All the modifiers penetrated better into sapwood than hardwood; however, there were significant differences in the impregnation behavior of the modifiers. As regards the effect of heat treatment, generally the moisture properties were improved and mechanical strengths impaired with increasing treatment temperature. In contrast to previous studies, the bending strength increased after melamine impregnation and mild heat treatment. It is concluded that the properties of impregnated wood can be enhanced by moderate heat treatment.     

Static bending and toughness of wood polymer composites (yellow birch and basswood)

Wood polymer composites (WPC) were made from basswood and yellow birch using six cell lumen type polymer formulations. The study was designed to get insight into the influence of wood density and polymer formulation on certain WPC mechanical properties. Small specimens were tested for toughness, stiffness, hardness and bending strength using standard ASTM methods. Results showed that stronger and stiffer polymers produce tougher and stronger WPC, but the effect is small. Thus, there is a wide range of polymer properties which produce useful WPC properties. Study of the fracture surfaces using Scanning Electron Microscopy (SEM) showed that WPC made with different polymers fractured differently and polymer containing a coupling agent bonded to the cell wall. However the cell wall bonding had no noticeable influence on WPC mechanical properties.     

Effects of fiber length and orientation on elasticity of fiber-reinforced plywood

Short carbon fibers, a reinforced material in wood veneer composites, were used to investigate the effects of fiber length and orientation of fibers on the elasticity of plywood. The technical feasibility, elasticity, and strength of the reinforced plywood with short carbon fiber were evaluated. In a short fiber reinforcement system, the fiber length does not directly influence the reinforcement in Cox's theory when the fiber length exceeded a certain length. When the length of short carbon fiber is beyond 3 mm, the high reinforced result was obtained in the experiment. However, if fiber length was too long, the reinforced result was less owing to the bridge between fibers and the increase of holes. The optimum fiber length must be considered. The orientation of fibers has a strong influence on the reinforcement. Unidirectional, perpendicular, and random orientation displayed different influence on the elasticity. Experimental results were discussed with Cox's method. Reinforced plywood with short carbon fibers in random orientation has a higher shear modulus and bending strength than the controls, in addition to other mechanical properties.