聚L-乳酸/聚丁二烯基聚氨酯的合成与表征

以乙二醇和L-乳酸熔融直接缩聚制备双端羟基聚L-乳酸预聚物(PLLA),并用1H、13C-NMR、DSC、XRD对PLLA结构和性能分析表征.以液化二苯基甲烷二异氰酸酯(MDI)为偶联剂,端羟基聚L-乳酸和端羟基聚丁二烯(HTPB)偶联反应制备橡胶改性聚乳酸基聚氨酯弹性体,并用FT-IR,1H、13C-NMR对聚合产物进行结构表征确认.DSC测试结果表明聚氨酯有聚丁二烯段和聚乳酸段两个玻璃化转变温度,熔融温度基本在130℃.随着聚丁二烯含量的增加,结晶衍射峰逐渐消失,聚氨酯的拉伸强度降低,断裂伸长率增加.断面扫描电镜结果显示聚氨酯呈微相分离结构和弹性断裂.

Synthesis and characterization of poly(L-lactic acid)/polybutadienebased polyurethanes

Hydroxyl-terminated poly(L-lactic acid)(PLLA) was prepared by melt condensation process with ethylene glycol.Lactic acid-based polyurethanes(PU) modified by rubber were prepared via the coupling reaction between hydroxyl-terminated poly(L-lactic acid)(PLLA) and polybutadiene(HTPB) prepolymers with methylene diphenyldiisocyanate(MDI) terminals.The chemical structures of the resulting product were confirmed with FT-IR,1H,13C NMR,and GPC.DSC spectra indicated that the Tm of the resulting polymers was close to the prepolymer PLLA.The copolymers had two Tg,that is,the Tg1 of the polybutadiene soft segment and the Tg2 of the PLLA hard segment,suggesting unmiscibility and phase separation between the soft and hard segments.With increasing PB content in the chain of the polyurethanes,the diffraction peaks of the polyurethanes disappeared slightly observed by XRD and the tensile strength of the samples decreased and the strain of the samples increased.The SEM analysis of ruptured surface of the polyurethanes showed the morphology is similar to the micro-phase separation structure and attributed elastic rupture.