含较高立构缺陷聚乳酸的非等温结晶动力学

Non-isothermal crystallization kinetics of poly(L-lactide-co-meso-lactide)

用非等温结晶动力学研究了聚乳酸(PLA)的结晶行为,利用Hoffman-Weeks外推法以及Baur等提出的方程反推出PLA中的右旋组分摩尔分数为7.2%。较高的右旋组分摩尔分数是PLA结晶过程中成核速率低的主要因素。添加质量分数为2%滑石粉等成核剂后,PLA结晶速率没有明显提高;含10%滑石粉的PLA结晶速率略上升,但其结晶温度靠近玻璃化转变温度,链段运动受到限制。添加质量分数为10%的聚乙二醇作为增塑剂后,PLA结晶速率明显提高。成核剂与增塑剂复配体系的"结晶速率系数"由单纯成核剂的15.0h^(-1)提高至40.8h^(-1)。根据Mo Zhisen等的分析法得到复配体系PLA的成核特征值为1.5。

The crystallization of poly（L4actide-co-meso-lactide） was studied in the terms of non-isothermal crystallization kinetics. The D-isomer molar content of the polylactide was 7.2% as calculated by Hoffman- Weeks plot and the equation proposed by Baur. The relatively high amount of D-isomer was the main reason for the low nucleation rate of the polylactide during the crystallization process. The crystallization rate of the polylactide did not rise noticeably after adding 2% in mass fraction of nucleating agent such as talc; though the crystallization rate of the polylactide containing 10% of talc by mass had slightly increased, the molecular chain movement of the polylactide was restricted because the polylactide crystallized at a temperature near its glass transition temperature. Adding 10% in mass fraction of polyethylene glycol as plasticizer raised the crystallization rate sharply. The crystallization rate coefficient of the polylactide compounded with the nucleating agent and plasticizer increased to 40.8 h-1 from 15.0 h-1 of the polylactide containing merely the nucleating agent. The nucleation value of the trinary polylactide composite was determined to be 1.5 by Mo＇s method.