【作者】 李光禄；

【导师】 祁阳；

【作者基本信息】 东北大学 ， 材料物理与化学， 2019， 博士

【摘要】 木塑复合材料（Wood Plastic Composite,简称WPC）,是以木纤维或植物纤维为填充/增强材料,以聚乙烯（PE）、聚丙烯（PP）、聚氯乙烯（PVC）、聚苯乙烯（PS）等热塑性塑料为基体材料,经挤压、注塑或热压成型所制成的复合材料。WPC兼具木材和塑料的优点,其防虫防腐性能、使用寿命优于木材,其硬度、自然降解性优于塑料。作为新型结构材料,目前WPC已用于建筑、汽车、造船、运输、园林、家装等众多行业。WPC研究与开发的关键问题是亲水性植物纤维与疏水性聚合物的界面相容性。改善WPC界面相容性的途径通常采用添加界面相容剂、塑料表面接枝改性和植物纤维化学改性。在WPC中使用界面相容剂,能在一定程度上改善材料界面相容性,但不能从根本上克服结构缺陷。植物纤维经过醚化、酯化等化学改性后,成为具有一定疏水性和热塑性的材料,能够改善植物纤维与热塑性塑料的界面相容性。本文分别以天然稻草为原料,以氯化苄、环氧氯丙烷为醚化剂,以乙酸酐为酯化剂,分别对稻草进行醚化和酯化改性。以改性稻草为填充体,以聚乙烯（PE）为基体,通过共混和挤出,制备改性稻草/PE复合材料。研究共混条件对复合材料微观结构和力学性能的影响,研究复合材料的生物降解和光降解性能,讨论改性稻草的表面极性,初步探讨稻草醚化反应的机理。与纯的PE相比,改性稻草/PE复合材料的拉伸性能和断裂伸长率有所下降,但均优于天然稻草/PE复合材料。当稻草含量为10%时,环氧氯丙烷改性稻草/PE、苄基化稻草/PE和乙酰化稻草/PE的拉伸强度分别比天然稻草/PE的拉伸强度高19.0%、6.4%和23..4%。环氧氯丙烷改性稻草/PE、苄基化稻草/PE和乙酰化稻草/PE的断裂伸长率分别比天然稻草/PE的断裂伸长率高200.9%、40.0%和69.0%。稻草的表面极性可用表面自由能来衡量。分别以氢氧化钠、硅烷偶联剂KH-550、氯化苄和乙酸酐对天然稻草进行改性处理。改性后,改性稻草的极性表面自由能均降低,降低的程度从高到低为,乙酰化稻草≈苄基化稻草>碱处理稻草>偶联剂稻草。分别以浑河水和土壤为接种源,以降解过程中的样品的增重率和介质水中葡萄糖含量的变化,考察稻草/PE复合材料的生物降解性能。在100天试验周期中,纯PE材料的质量几乎没有变化,说明没有任何的降解。稻草含量增加,生物降解程度提高。天然稻草/PE复合材料的生物降解速率略高于改性稻草/PE复合材料,但没有显著差别。在QUV/basic老化试验箱中模拟日光条件对复合材料进行加速光降解试验。复合材料的光降解性规律与生物降解的结果相似。通过分析不同改性反应时间的改性稻草的FT-IR、¹³C-NMR、元素组成、中性糖含量和百分增重率等,研究改性稻草组成和微观结构的变化,推测改性反应机理。醚化剂为环氧氯丙烷和氯化苄,醚化反应主要发生在纤维素环的C-2、C-3和C-6位置,改性后,羟基数量减少,极性降低。我国稻草资源丰富,目前,稻草主要用作燃料和大牲畜饲料。用稻草代替木材和塑料,大大提高了稻草的价值,对保护环境和保持可持续发展,都有重要意义。本项目的研究成果,可推广到其它农作物,如小麦,甘蔗渣、麻等,应用前景十分广阔。更多还原

【Abstract】 Wood-plastic composites（WPC）are composites made by extrusion,injection or hot-pressing with wood or plant fibers as filling/reinforcing materials,polyethylene（PE）.polypropylene（PP），polyvinyl chloride（PVC）,polystyrene（PS）and other thermoplastic plastics as matrix materials.WPC has the advantages of both wood and plastics.Its pest-proof and anti-corrosion performance and service life are superior to wood,and its hardness and natural degradation are superior to plastics.As a new structural material,WPC has been used in many industries,such as construction,automobile,shipbuilding,transportation,gardening,home decoration and so on.The key problem in the research and development of WPC is the interfacial compatibility between plant fibers and polymers.The ways to improve the interfacial compatibility of WPC are usually to add interfacial compatibilizers,surface grafting modification of plastics and chemical modification of plant fibres.The use of interfacial compatibilizer in WPC can improve the interfacial compatibility of materials to a certain extent,but it cannot overcome the structural defects fundamentally.After chemical modification,such as etherification and esterification,plant fibers become hydrophobic and thermoplastic materials,which can improve the interfacial compatibility between plant fibers and thermoplastic plastics.In this work,natural straw was used as raw material,benzyl chloride,epichlorohydrin as etherifying agent,acetic anhydride as esterifying agent,respectively,to etherify and esterify rice straw.Modified rice straw/PE composites were prepared by blending and extrusion with modified rice straw as filler and polyethylene（PE）as matrix.The effects of blending conditions on the microstructures and mechanical properties of the composites were studied.The biodegradability and photodegradability of the composites were studied.The surface polarity of the modified straw was discussed.The mechanism of etherification reaction of the straw was preliminarily discussed.Compared with pure PE,the tensile properties and elongation at break of modified rice straw/PE composites decreased,but they were better than those of natural rice straw/PE composites.When the content of rice straw was 10%,the tensile strength of rice straw modified with epichlorohydrin/PE,benzylated rice straw/PE and acetylated rice straw/PE were 19.0%,6.4%and 23.4%higher than that of natural rice straw/PE,respectively.The elongation at break of rice straw/PE modified by epichlorohydrin,benzylated rice straw/PE and acetylated rice straw/PE were 200.9%,40.0%and 69.0%higher than that of natural rice straw/PE,respectively.Surface polarity of straw can be measured by surface free energy.Natural rice straw was modified by sodium hydroxide,silane coupling agent KH-550,benzyl chloride and acetic anhydride,respectively.After modification,the surface free energy of the modified rice straw decreased from high to low:acetylated rice straw≈benzylated rice straw>alkali treated rice straw>coupling agent rice straw.The biodegradability of rice straw/PE composites was investigated by using Hunhe River water and soil as inoculation sources,and the weight gain of samples and the change of glucose content in medium water as biological degradation indexes.During the test period of 100 d,the quality of pure PE material has hardly changed,indicating that there is no degradation for PE.With the increase of straw content,the degree of biodegradation increased.The biodegradation rate of natural straw/PE composites was slightly higher than that of modified straw/PE composites,but there was no significant difference between them.The accelerated photodegradation of composites under simulated sunlight conditions was carried out in QUV/basic aging test box.The photodegradability of the composites is similar to that of the biodegradable composites.By analyzing FT-IR,¹³C-NMR,elemental composition,neutral sugar content and percentage weight gain of modified rice straw with different reaction time,the changes of composition and microstructure of modified rice straw were studied,and the reaction mechanism was speculated.For the etherification reagents of epichlorohydrin and benzyl chloride,the etherification reaction mainly takes place at the C-2,C-3 and C-6 positions of cellulose rings.After modification,the number of hydroxyl groups decreases and the polarity decreases.China is rich in straw resources.At present,straw is mainly used as fuel and livestock feed.Replacing wood and plastics with straw will greatly improve the value of straw,which is of great significance to environmental protection and sustainable development.The research results of this project can be extended to other crops,such as wheat,bagasse,hemp and so on.The application prospect is very broad.更多还原