多臂蓖麻油-乳酸共聚物的制备及其共混增韧聚乳酸的研究

Poly(lactic acid) (PLA) has received widespread attention due to its good biocompatibility, biodegradability, excellent mechanical and processing properties. However, the inherent brittle nature limiting its use in some applications . It is usually an effective method to improve its performance that polylactic acid blends with petroleum-based polymers . Unfortunately, this method is difficult to obtain a completely biodegradable polylactic acid material. The project aims to synthesize polyesters baed on castor oil, which are different degrees of branching of castor oil - lactic acid copolymer and have good compatibility with matrix polylactic acid.Copolymer are used to modify polylactic acid through melt blending in order to prepare fully biodegradable, toughness good polylactic acid.Through the regulation of the blending ratio, the molecular weight and its distribution, a branched chain length of the multi-arm polylactic acid, the number of branch chain, block composition, and the processing temperature and other conditions, we can prepare completely biodegradable polylactic acid-modified materials; which have different properties and crystallization behavior . The relationship between molecular structure of the copolymer, polylactic acid toughening, the polylactic acid crystal are studied.We ultimately achieve the comprehensive improvement of the processing properties and the mechanical properties of the polylactic acid.

聚乳酸具有良好的生物相容性、生物可降解性以及优异的机械性能和加工性能，受到广泛的关注。聚乳酸的固有脆性，限制其应用；聚乳酸与通常石油基增韧材料共混，是改善其性能的有效方法；该方法难以获得完全可降解聚乳酸材料。本项目从天然生物质材料蓖麻油出发，合成不同臂数、组成蓖麻油-乳酸共聚物，增加与基质聚乳酸界相容性；将其熔融共混改性聚乳酸，制备可完全生物降解、韧性好聚乳酸。通过调控共混比例、分子量及其分布、多臂聚乳酸的支链长度、支链数目、支链嵌段组成以及加工温度等条件，制备具有不同性能与结晶行为、完全可降解聚乳酸改性材料；研究多臂共聚物的分子结构、聚乳酸的增韧、聚乳酸结晶之间关系，最终实现聚乳酸的加工性能和力学性能的综合改善。

作为一种半结晶的生物基可降解聚酯材料，聚乳酸(PLA)具有高的力学强度和模量，可以替代石油基聚丙烯(PP)、聚苯乙烯(PS)等工程塑料，广泛应用于一次性餐具、医疗器材、3D打印耗材等。聚乳酸来源于生物质材料，具有强力的价格竞争优势；另外优异的力学性能、可降解性能，使其成为综合性能最好、产业化规模最大的可降解材料。然而，聚乳酸纯树脂固有的脆性、低的熔体强度和热稳定性，限制其在包装膜材料领域的应用。本项目以丁二酸、丁二醇为原料，经过缩聚合成端羟基的大分子引发剂HO-PBS-OH，然后引发丙交酯的开环共聚合制备PLA-PBS-PLA的嵌段共聚物。研究PLA与PBS的相对组成对三嵌段PLA-PBS-PLA结晶的影响。利用三嵌段共聚物PLA-PBS-PLA作为增韧剂，以聚(乳酸-丙烯酸缩水甘油醚)(PLA-PGMA)作为扩链剂，经过反应共混改性聚乳酸；考察改性后树脂的力学性能（强度、断裂伸长率）、熔体强度、结晶性能和相容性等。结果表明，我们得到高柔韧性和高熔体强度的改性聚乳材料，将其应用于PLA购物袋的生产。另外，我们将基于聚乙二醇(PEG-1500)的聚氨酯与聚乳酸反应共混，以亚磷酸三苯酯(TPP)作为酯交换剂，克服聚乙二醇易吸水和迁移的缺点，得到高韧性共混材料；研究聚氨酯的硬段种类和添加量对共混物的热性能、形貌、力学和老化性能的影响。研究分子量、光学纯度、光学异构体、支化结构对聚乳酸的基本性质的影响。