【作者】 杜华；

【导师】 王清文； 王伟宏；

【作者基本信息】 东北林业大学 ， 生物材料工程， 2012， 博士

【摘要】 木塑复合材料经常使用在户外条件下,其耐气候性能尤为重要。本文重点研究了稻壳粉／高密度聚乙烯(Rice-hull/HDPE简写为RH/HDPE)复合材料的耐老化性能。将稻壳粉含量不同的RH/HDPE复合材料试件在人工加速紫外老化条件下进行老化处理,利用扫描电子显微镜对复合材料表面微相结构进行观察和分析,然后通过静态力学测试、色差分析、傅立叶变换红外光谱和X-射线光电子能谱仪等方法分析紫外老化后复合材料各种性能变化及样品表面化学变化情况。揭示了各组分含量与复合材料的耐候性能之间的关系及紫外线吸收剂、无机颜料和受阻胺光稳定剂等不同类型光稳定剂对RH/HDPE复合材料耐老化性能的影响,最终确定了不同光稳定剂复配的效果。研究结果为提高木塑复合材的耐候性提供了实用工艺配方,为开发新型环保木塑复合材料奠定了理论基础。主要研究结果如下：(1)在紫外老化过程中,所有样品明度(L*)都增加,但RH/HDPE复合材料样品的明度变化(△L*)程度远大于纯HDPE的,并且在紫外老化的第一个250h里变化最大。同时,复合材料表面产生裂纹,弯曲性能降低；随着稻壳粉含量的增加和老化时间的延长,△L*程度增大,即样品褪色越来越严重,表面裂纹越来越多,弯曲性能损失越来越大,复合材料表面氧化程度也不断增大。(2) FTIR对紫外老化前后纯HDPE和RH/HDPE复合材料样品表面的化学变化的分析结果表明,将稻壳粉加入到HDPE中带来了大量的羰基,使复合材料表面羰基指数增大。在紫外老化过程中,RH/HDPE复合材料中HDPE分子发生断链,羰基指数明显增加。断链和交联反应是同时发生,HDPE的结晶度产生一定变化。(3)增加稻壳粉含量,使RH/HDPE复合材料表面的纤维指数和木质素指数增大。在紫外老化过程中,纤维指数和木质素指数损失增大；紫外老化2000h后,稻壳粉含量不同的复合材料其木质素指数都下降到近似值,相互之间没有明显差别,说明木质素对紫外光很敏感,几乎降解完全。(4)紫外线吸收剂和颜料在一定程度上能够减少RH/HDPE复合材料表面褪色和裂纹的产生,减小弯曲性能的损失,延迟复合材料表面氧化的发生。UV-326比UV-531的效果更好；颜料中炭黑的效果最好。受阻胺光稳定剂不能有效减小复合材料表面明度的变化,褪色程度加大,但能有效保护复合材料的弯曲性能,减小复合材料表面的氧化程度。在紫外老化过程中,不同种类光稳定剂的联合使用产生不同效果的协同效应,可有效减小复合材料表面明度和颜色的变化,降低复合材料弯曲强度和弯曲模量的损失。其中,UV-326(苯并三唑类)与L-944(高分子量的三杂氮苯类)协同效果最好。更多还原

【Abstract】 Wood plastic composites are often used outdoor. Its resistance to weathering is concerned. This paper focuses on evaluating the properties of Rice-hull/HDPE (RH/HDPE) composites after exposed to accelerated UV-weathering. RH/HDPE composites with different rice hull content was weathered under the artificial accelerated UV-weathering test conditions.The configuration of the composite surfaces were observed and analyzed with scanning electron microscope, and then the performance of composites and surface chemical changes after the aging were evaluated by static mechanics test, color difference analysis, Fourier transform infrared (FTIR) spectrum analysis, and X-ray photoelectron. The relationship between components in RH/HDPE composites and the weathering resistant quality of composite were analyzed, and then the effect of ultraviolet absorbers, inorganic pigments, a resistance amine light stabilizer, and other light stabilizers was investigated. In the meanwhile, synergistic effect of different light stabilizer was discussed. Eventually the formula that resist to UV weathering was confirmed. This research would provide theoretical foundation for improving wood and plastic composites’weathering resistance, and establish a process for evaluate the application of wood plastic composites. The main research conclusions are as follows:(1) In the process of UV-weathering, the lightness (L*) of all samples increased, however,. L*of RH/HDPE composites varied in a larger margin than pure HDPE. In the first250h of exposing, L*changed most. In the meanwhile, surface cracks came into being and bending performance decreased. With the increase of rice-hull powder content and UV weathering time, L*continuously increased, i.e. samples faded aggravatingly, and surface crack became more serious, flexural property decreased and surface oxidation increased also.(2) Surface chemical variation of pure HDPE and RH/HDPE composite material before and after UV-weathering was analyzed with FTIR. The addition of rice-hull powder to HDPE introduced more carbonyl, which resulted in more carbonyl index presented in RH/HDPE composites sample. In the process of UV-weathering, HDPE molecule chains break, the carbonyl index of RH/HDPE composites surface increased significantly. Chain cession and crosslinking happened simultaneously. These made the crystallinity of HDPE change.(3) Cellulose index and lignin index of RH/HDPE composites increased with the increasing of rice-hull powder content. During UV-weathering, the loss of cellulose index and lignin index increased. at the end2000h UV-weathering, the lignin index of composite materials with different rice-hull powder content decreased to lowest value, and there was no significant differences among each other. Analysis indicated that lignin is very sensitive to ultraviolet light, and almost degraded completely. (4) Ultraviolet absorber agent and pigment reduced fade and crack on the surface of RH/HDPE composites, reduced the loss of bending performance, and delayed the occurrence of oxidation in composites. UV-326reacted better than UV-531, and carbon black is the best pigment to protect composites. Resistance amine light stabilizer did not obviously reduce the lightness of composites, namely fading degree increased, however, it protected the bending quality from losing and reduced the oxidation magnitude of the composites. During UV-weathering, the combination of different kinds of light stabilizer has cooperative effect, which effectively reduced lightness and total color changing, and reduced the loss in the flexural intensity and modulus. Among which the collaborative effect between UV-326(benzotriazoles) and L-944(triazine) was the best.更多还原