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采用二步法由乳酸制备丙交酯,由丙交酯的开环聚合制备高分子量的聚乳酸。实验采用正交设计方法,通过改变催化剂种类、催化剂用量、脱水时间、环化时间四个主要影响因素进行实验,根据实验结果选择最好的丙交酯制备的实验方案。再次运用正交设计方法,通过改变催化剂种类、催化剂用量、反应时间、反应温度得到性能和分子量不同的聚乳酸,采用乌氏黏度计方法测定聚乳酸的分子量,利用傅立叶红外光谱和扫描电镜对聚乳酸的结构和形貌进行表征。
A two-step method was used to prepare lactide from lactic acid. Polylactic acid with high molecular weight was prepared by ring-opening polymerization of lactide. The orthogonal design method was used in the experiment. The experiment was carried out by changing four main influencing factors: catalyst type, catalyst dosage, dehydration time and cyclization time. According to the experimental results, the best experimental scheme of lactide preparation was selected. The orthogonal design method was used again to determine the molecular weight of polylactic acid by changing the type of catalyst, the amount of catalyst, the reaction time and the reaction temperature, and the molecular weight of polylactic acid was determined by Ubbelohde viscometer. Fourier transform infrared spectroscopy and scanning electron microscopy The structure and morphology of lactic acid were characterized.