Non-isothermal crystallization kinetics of ramie fiber-reinforced polylactic acid biocomposite

Ramie fiber (RF) reinforced polylactic acid (PLA) laminated biocomposite was prepared by hot-press molding using the non-woven ramie fibers and short PLA fibers. To understand the effect of ramie fibers on the crystallization behaviors of PLA, we study the non-isothermal crystallization kinetics of pure PLA and PLA/RF biocomposite. The crystallization behaviors of pure PLA and PLA/RF biocomposite with 40 wt% non-woven ramie fibers first were determined by differential scanning calorimetry (DSC). The results show that the addition of the RF could propel the crystallization process of PLA, during which the RF played a role in heterogeneous nucleation. Then, we used several models to analyze the crystallization behaviors during cold crystallization of PLA and PLA/RF biocomposite. The Jeziorny model for non-isothermal crystallization kinetics indicated that the crystallization process of PLA and PLA/RF biocomposite could be divided into two stages, and the addition of RF would not change the crystallization mechanism of PLA compared with that of pure PLA, which also was confirmed by the combination model of Ozawa equation and Avrami equation. In addition, the Doyle-Ozawa model's results revealed that when the relative crystallinity increased, the local apparent activation energy of PLA and PLA/RF biocomposite showed a gentle downward trend, and the average local activation energy was consistent with the apparent activation energy. In general, the addition of RF weakened the interaction between PLA chains and reduced the energy barrier of PLA in the crystallization process for the ramie fiber-reinforced PLA biocomposite.