基于工艺参数在线监测的聚乳酸生物塑料注射成型机理

Injection Molding Mechanism of PLA Bioplastics Based on Online Monitoring of Processing Parameters

利用自主搭建的工艺参数在线监测平台系统研究了熔体压力、熔体温度及注射速度等注射成型工艺参数对聚乳酸(PLA)生物塑料试样拉伸强度的影响规律,利用差示扫描量热仪和扫描电子显微镜等测试表征手段研究了不同工艺状态条件下PLA试样结构的变化规律,总结了熔体压力、熔体温度、注射速度与PLA试样力学性能、结构之间的作用机理。结果表明,在实验条件范围内,PLA试样成型时存在一个最佳工艺状态,即熔体温度180℃、熔体压力8 MPa、注射速度为注塑机最大注射速度的40%,在该状态下所成型试样的拉伸强度达到最佳;PLA成型过程的结晶存在一个由熔体压力所引发的最佳诱导结晶应力;对比熔体温度和熔体压力,注射速度是影响PLA结晶形貌的不敏感工艺参数。

The influences of injection molding process parameters such as melt pressure,melt temperature and injection speed on the tensile strength of bioplastics such as polylactic acid(PLA)products were studied systematically based on the self built online monitoring platform of process parameters.The change rule of PLA product structure under different process conditions was studied by using DSC,SEM.The interaction mechanism between the melt pressure,melt temperature,injection speed and mechanical properties,structure of PLA products was summarized.The results show that there is an optimal processing condition for PLA products in the range of experimental conditions,that is,the melt temperature is 180℃,the melt pressure is 8 MPa,and the injection speed is 40%of maximum injection speed of injection machine,under which the tensile strength of PLA is the best.There is an optimal induced crystallization stress caused by melt pressure in the crystallization of PLA products,and the injection speed is the insensitive process parameters affecting the PLA crystal morphology comparing with the melt temperature and melt pressure.