【作者】 李春桃；

【导师】 王伟宏； 王清文；

【作者基本信息】 东北林业大学 ， 生物材料工程， 2010， 硕士

【摘要】 木塑复合材料(WPC)是以生物质纤维材料作为增强材料,与塑料复合而成的一类新型高性能、高附加值的绿色环保材料。然而,由于极性的生物质纤维与非极性的塑料基体之间缺乏良好的相容性,导致二者的界面不能有效结合,从而不能充分利用纤维的强度,致使所得的复合材料性能受到影响。因此,改善二者的相容性,增强其界面结合强度,是提高木塑复合材料性能的关键点之一。本文选用六种分子结构具有递变规律、代表性的硅烷偶联剂(分别为A-151、A-171、DB-550、DB-560、DB-570及DB-580)对杨木木粉进行改性处理,然后与高密度聚乙烯(HDPE)混合挤出制备木粉/HDPE复合材料,通过对比复合材料的力学及耐水性能,分析断面微观形态、傅里叶变换红外光谱(FTIR)及流变性能等,优选出改性效果最佳的硅烷偶联剂。最后针对最佳硅烷偶联剂的改性工艺进行优化,具体包括偶联剂的添加量、偶联剂的溶液浓度及自由基引发剂过氧化二异丙苯(DCP)的添加量等参数。与未处理的木粉/HDPE复合材料相比,采用硅烷偶联剂处理木粉制备的复合材料的力学强度和耐水性能得到不同程度的提高,其中A-171的处理效果最好。扫描电子显微镜(SEM)观察表明,经硅烷偶联剂处理后,复合材料的断面微观形态发生变化,木粉与基体之间的结合增强,两相的界面相容性得到了有效改善。对比经A-171处理前后木粉的FTIR谱图可知,用A-171处理后的木粉的红外谱图在770cm-1处出现硅烷醇白聚产生的Si-O-Si键的特征吸收峰；另外1108cm-1处吸收峰加强,归因于Si-O-C吸收峰的出现,说明A-171和木粉之间可能发生了缩聚接枝反应。随着DCP含量和A-171含量的增加,复合材料的力学强度逐渐增大,耐水性逐渐提高；当DCP的含量为0.13%、A-171含量为4%时,弯曲、拉伸强度及耐水性达到最大值；再继续增加DCP含量,复合材料的力学强度和耐水性开始下降,这可能与DCP用量较高时引发HDPE降解有关；当A-171含量超过4%时,随着A-171含量的增加,复合材料的力学强度和耐水性增加不明显；冲击强度增加的程度却仍然很大,添加量超过6%后冲击强度增长缓慢；A-171的溶液浓度对复合材料的力学强度的影响不大,但随着A-171溶液浓度的增加,耐水性降低。流变学研究表明,不同种类硅烷偶联剂及不同用量的A-171对复合材料的线性粘弹性范围基本没有影响,但随着应变幅度的继续增大,存储模量G’开始下降,表现出非线性粘弹性行为；与未处理的木粉,HDPE复合材料相比,经过不同种类硅烷偶联剂及不同用量的A-171处理后,复合材料的储能模量G’和粘度η*均有所降低,而损耗角正切值tanδ却有所增加,但差异不大；随着频率增大,黏度均不断下降,表现出剪切变稀行为。更多还原

【Abstract】 Wood plastic composites (WPC), made from various plastics and biomaterials as reinforced materials, are a new type of green environmental composites with high performance and added value. However, due to the poor interfacial compatibility between the polar biomaterials and the nonpolar plastics matrix, the interfacial bonding between the two components is not effective, and it can’t make full use of the fiber strength, which in turn influence the performance of composites. Therefore, to improve the interfacial compatibility and enhance the interfacial bonding between biomaterial and plastics are key points for evaluating the performance of the composite. In this paper, poplar wood fibers were modified with six kinds of representative silane coupling agents (A-151, A-171, DB-550, DB-560, DB-570 and DB-580, respectively) with different molecule structure, then blended with high density polyethylene (HDPE) to prepare composites by extrusion. The most effective silane coupling agent was selected out by comparing the mechanical performances and water resistance properties, and analyzing the morphology of the fracture surface, FTIR spectra and rheological properties of the composites. Then optimized the modification technology of this best silane coupling agent, included the amount and solution concentration of the silane and the amount of dicumyl peroxide (DCP), which used as free radical initiator.Compared to the untreated wood flour/HDPE composite, the mechanical properties and water resistance were all improved after treated with the six different silane coupling agents, and A-171 was the most effective. The observation of scanning electron microscope (SEM) indicated that the morphology of the fracture surface of the composites after treated was changed and the interfacial bonding between wood flour and matrix was reinforced, the interfacial compatibility of the two phases was effective improved. Compared to the FTIR. spectra of untreated wood flour, there was a new characteristic absorption peak at 770cm-1 belongs to Si-O-Si bond generated by self-polymerization of silanol and a reinforced one at 1108cm-1 belongs to the covalent bond Si-O-C after treated with A-171, which indicated the possible polycondensation grafting reaction between A-171 and wood flour.The mechanical strength and water resistance of the composites were all increased with increasing the amount of DCP and A-171. When the amount of DCP was 0.13% and A-171 was 4%, the flexural and tensile strength and water resistance were all maximum. Continue to increase the amount of DCP, the mechanical strength and water resistance were begin to decrease, which may attributed to the HDPE degradation caused by higher amount of DCP. When the amount of A-171 was exceeded 4%, the increasing extent of flexural and tensile strength of the composites was smaller with the increase of the amount of A-171, but the impact strength increasing obviously until the amount of A-171 exceeded 6% The solution concentration of A-171 had slight effects on mechanical properties of composites, but the water resistance of composites was decreased with the increase of solution concentration of A-171.Rheology study indicated that different kinds of silane coupling agents and different amount of A-171 had little effect on the linear viscoelastic regions (LVR), but the storage modulus G’ of composites was decreased with the increasing of strain amplitude, exhibited nonlinear viscoelastic properties. The G’ and viscosityη*of the composites treated with different kinds of silane coupling agents and different amount of A-171 were decreased compared to the untreated wood flour/HDPE composite, but the loss tangent tan8 of the treated wood flour/HDPE composites were all increased with little difference. The viscosity of the composites was continuously decreased with the increase of frequency, showed the shear thinning behavior.更多还原