基于异氰酸酯衍生物的聚乳酸熔融扩链工艺、动力学及结构表征

以微波法氧化锌（ZnO）柱撑有机皂石催化丙交酯开环聚合的聚乳酸(PLA)为原料，分别采用二苯基甲烷二异氰酸酯 (MDI)和六亚甲基二异氰酸酯(HDI)进行熔融扩链反应，研究了扩链剂的用量和反应时间对PLA相对分子质量的影响，并对PLA的扩链动力学进行了研究。结果表明，最优的扩链反应工艺参数为：反应温度180 ℃，nNCO：nOH为2.5：1，MDI扩链时间为45 min，HDI扩链时间为30 min；MDI和HDI扩链反应的表观速率常数分别为6.081×10^3、6.98×10^3 g/(mol·min)。

Molten Chain Extension Technology,Kinetics and Structure Characterization of Poly(lactic acid) Based on Isocyanate Derivatives

Poly（lactic acid）(PLA) was prepared by ring opening polymerization of D, L-lactide with zinc oxide (ZnO) pillared organic saponite under microwave assistance. The molten chain extension reaction of PLA was investigated with hexamethylene diisocyanate (HDI) and 4, 4-diphenylmethane diisocyanate (MDI) as chain extenders. The effect of reaction time and addition amount of chain extender on the molecular weight of PLA was also studied. The optimum parameters of the chain extending reaction were as follows: the ratio between nNCO to nOH was 2.5：1, the reaction temperature was 180 ℃, the chain extension time of MDI was 45 min, and the chain extension time of HDI was 30 min. Kinetics experiments indicated that the chain extender showed the apparent rate constants of MDI and HDI were 6.081×10^3 g/(mol·min)，6.98×10^3 g/(mol·min), respectively.