Wood plastic composite has gradually gained importance recently all over the world. The composite manufacturers continue to search for new and cheaper lignocellulosic materials or annual plant residues as an alternative to wood. Tea is the most popular beverage in the world. The worldwide consumption of tea is about 4.5 million tons annually, which is far more than that of coffee, beer, wine and carbonated drinks. It always ends up with lots of waste tea leaves, stalks and dusts daily during the process of tea production and consumption. The tea residue is made of fibrous biomass, which brings the increasing problems of solid waste and disposal in many countries. Studies have been conducted to determine potential uses of waste tea residues such as adsorbent for synthetic dyes and heavy metals, fertilizer, mushroom growing medium, energy source, livestock and poultry feed, and particleboard. The tea residue to use as organic filler in polymer composites has showed a great prospect because of its lignocellulose behavior and low cost, but there have been few researches about the work, and no researches about the outdoor application or weathering mechanism of polymer composites by using waste tea residues as organic filler so far. Because the chemical compositions and fiber morphology of tea fiber in the waste tea residue were quite different from that in wood residue, in order to make high-valued use of the waste tea residue, the wasted tea stalk/Polypropylene (TS/PP) composites were manufactured by open mill and injection molding machine, with maleic anhydride grafted polypropylene (MAPP) as coupling agent. At the same time aimed to explore the outdoor application and weathering mechanism of TS/PP composites, the effects of freeze-thaw cycles accelerating weathering on the mechanical properties, color change and thermal behavior of the composites were investigated, the surfaces morphology of composites were investigated by SEM (scanning electronic microscopy), and the chemical structures and weathering mechanism were also analyzed by FTIR (Fourier transform infrared spectrum) and TGA (thermogravimetric analysis) The results showed that the TS/PP composites exhibited great color change and large decrease in mechanical properties. The corresponding lightness change∆L*, redness change∆a*, yellowness change∆b*and the color change∆E were 16.41, 2.80, 9.03 and 18.93, respectively after freeze-thaw cycles for 12 times. The retentions of bending, notched impact strength, flexural modulus and hardness of the composites were 28.9%, 40.1%, 34.5% and 86.5%, respectively after freeze-thaw cycles for 12 times. The vicat softing point and the largest degradation temperature of the composites were decreased by 2.9 and 4℃ respectively. The IR (infrared spectrum) absorption peak corresponding to tea stalk became weaken, which indicated the degradation of lignin in tea stalk during the freeze-thaw accelerating weathering. But the largest degradation temperature and IR absorption peak corresponding to PP component in TS/PP composites changed little after freeze-thaw cycles. The SEM (scanning electronic microscopy) images indicated that the micro cracks and folds appeared first on the surfaces of weathered composites after freeze-thaw cycles; and then the width, depth and quantity of cracks were increased with the increasing of the number of freeze-thaw cycles. There even appeared cross-like cracks or holes on the surface of the TS/PP composites when weathered by freeze-thaw cycles for 12 times.%为高值化利用茶产业剩余物资源，拓宽木塑复合材料中植物纤维来源，以废弃茶梗（tea stalk，TS）为有机填料，与聚丙烯（Polypropylene，PP）制备了TS/PP复合材料；同时为研究其户外应用和老化机制，考察了冻融循环老化对TS/PP复合材料力学性能、材色及热性能的影响，并用傅里叶红外光谱（Fourier transform infrared spectrum，FTIR）、扫描电镜（scanning electronic microscopy，SEM）等分析了复合材料的化学结构、表面形貌及老化机制。结果表明：在经历12次冻融循环老化后，复合材料的弯曲强度、缺口冲击强度、弯曲模量及硬度值保留率分别为28.9%、40.1%、34.5%和86.5%，复合材料的亮度变化值（∆L*）、红绿轴色品指数变化值（∆a*）、黄蓝轴色品指数变化值（∆b*）及色差值∆E分别为16.41、2.80、9.03和18.93；复合材料维卡软化点（vicat softing point，VSP）下降了2.9℃，茶粉组分的最快热降解温度降低了4℃；茶粉中木素苯环结构红外吸收峰强度减弱甚至消失，表明在冻融循环老化中茶粉中木素成分发生了降解。SEM显示随冻融循环次数增加，TS/PP 复合材料表面裂纹数量增多，裂纹深度和宽度增大，甚至出现交叉裂纹。该研究结果可为进一步探索茶塑复合材料制备及老化规律，提供试验数据和理论参考。
展开▼
