注射成型立构复合聚乳酸的热变形性能分析

Thermal Distortion Performance of Injection Molded Stereocomple Poly(lactic acid)

采用左旋聚乳酸(PLLA)和右旋聚乳酸(PDLA)为原料,采用熔融共混法制备了立构复合聚乳酸(SC-PLA)粉末,再通过注射成型制备了SC-PLA样条,并通过差示量热扫描仪(DSC)和热变形温度测定仪对SC-PLA粉末和样条的熔融、结晶情况和热变形性能进行了表征分析。结果表明,SC-PLA粉末的结晶能力与初始熔融状态直接相关;当熔融温度为220~230℃时,SC-PLA粉末的熔融稳定时间增加,有助于SC-PLA体系结晶,该温度适合SC-PLA的注射成型加工;SC-PLA样条中SC-PLA结晶度越高,均聚物PLA结晶度越低,越有助于样条热变形性能的提高;低注射温度和以SC-PLA粉末、PLLA、PDLA为原料成型有助于SC-PLA样条在220℃下加热再退火后获得较高的SC-PLA结晶度,其热变形温度最高可达到150℃以上;注射成型过程中,有利于保留更多SC-PLA晶体和提高SC-PLA结晶度的方式,有助于提高样条在退火后的热变形性能。

The stereocomple poly(lactic acid)(SC-PLA)powders were prepared through melt blending using poly(Llactic acid)and poly(D-lactic acid)as raw materials and then were injection molded to form SC-PLA parts. The melting,crystallization and thermal properties of SC-PLA powders and parts were characterized using a differential scanning calorimeter and a thermal deformation temperature tester. The results indicated that the crystallization ability of SC-PLA was related to the initial melting state. The melting stabilization time of SC-PLA increased in the melting temperature range of 220~230 ℃,which facilitated the crystallization and was suitable for injection molding of SC-PLA. The better the crystallization ability of SC-PLA with low crystallinity of homopolymer PLA,the higher was the heat distortion temperature of the injection-molded parts of SC-PLA. The crystallization ability of SC-PLA could be increased through decreasing injection temperature and using the formulation based on SC-PLA powders and PLLA/PDLA mixture. The injection-molded parts of SC-PLA achieved a maximum heat distortion temperature of over 150 ℃ after annealing. During injection molding,the heat distortion temperature of the samples after annealing could be improved through retaining more SC-PLA crystals and increasing the crystallinity of SC-PLA.