纳米二硫化钼对聚乳酸等温结晶行为的影响

Influence of Nano-MoS_2 on Isothermal Crystallization Behavior of PLA

采用熔融共混法制备聚乳酸/二硫化钼(PLA/MoS_2)纳米复合材料。通过差示扫描量热法(DSC)研究纳米MoS_2含量对PLA等温结晶行为的影响,采用Avrami方程分析纳米复合材料的等温结晶动力学,并采用X射线衍射(XRD)测试材料的结晶结构。由等温结晶动力学计算结果可知,加入MoS_2纳米粒子后,PLA基体的结晶速率显著提高。例如,当结晶温度(Tc)为110℃,MoS_2含量由0增至2.0%时,试样的结晶半时间(t1/2)可由纯PLA的8.5 min大幅降低至3.2 min。而当Tc为120℃,MoS_2含量由0增至2.0%时,试样的t1/2由纯PLA的11.4 min降低至3.8 min。同时,随着MoS_2含量的增大,PLA基体的最大结晶度也有一定程度增大,说明MoS_2起到异相成核剂作用。PLA/MoS_2试样的Avrami指数在2.6~3.1之间,可知在MoS_2存在下,PLA晶体主要为异相成核和三维生长。

PLA/MoS2 nanocomposites were prepared by using melt blending method. The effect of nano MoS2 content on the isothermal crystallization behavior of PLA was investigated by differential scanning calorimetry（DSC）; the Avrami equation was applied to analyze isothermal crystallization kinetics of the PLA/MoS2 samples. In addition, crystal structure of PLA/MoS2 samples was studied by using XRD measurement. The results of isothermal crystallization kinetics show that the crystallization rate of PLA matrix increases significantly after adding MoS2 nanoparticles. For example, while crystallization temperature is 110℃, and MoS2 content increases from 0 to 2.0%, half crystallization time（t1/2） of PLA matrix drastically decreases from 8.5 min down to 3.2 min. As another example, while crystallization temperature is 120℃, and MoS2 content increases from 0 to 2.0%, t1/2 of PLA matrix decreased from 11.4 min down to 3.8 min. Meanwhile, with the increase of MoS2 content, the maximum crystallinity of PLA matrix also increases to some extent, which shows that MoS2 acts as heterogeneous nucleating agent. The Avrami index of PLA/MoS2 sample is between 2.6 and 3.1. It is known that the PLA crystal is mainly heterogeneous nucleation and three-dimensional growth in the presence of MoS2.