Toward Heat-Resistant and Transparent Poly(l-lactide) by Tailoring Crystallization with an Aliphatic Amide as a Nucleating Agent

Poly(l-lactide) (PLLA) has been known as an important bioplastic with tremendous potential to replace some conventional fossil-based plastics; however, its commercial application still faces great challenges in terms of the implacable contradiction between high thermomechanical properties and exceptional optical transparency. Herein, we report a feasible and promising strategy to address this challenge by utilizing N,N-ethylenebis(12-hydroxystearamide) (EBH) as an efficient nucleating agent (NA) to tailor the crystallization of PLLA. The results show that the presence of EBH can not only accelerate the melt crystallization of PLLA but also remarkably decrease the size of the crystals formed in the crystallization at low temperatures of 80–90 °C. Further analysis indicates that the EBH molecules dispersed in PLLA melt could self-organize into nanofibrous network structures upon cooling, which can provide an extremely large nucleation surface for the growth of numerous nanosized crystals. Consequently, highly crystallized (the crystallinity is as high as 45%) PLLA sheets with an impressive combination of superb heat resistance and good transparency (the clarity is ca. 70%) have been successfully fabricated by melt processing with the aid of 0.4–0.8 wt % EBH. Our work offers a new opportunity to develop heat-resistant and transparent PLLA materials.