Regulation of Crystallization and Performance of Poly( l ‐lactic acid) by Melt Crystallization and Boron Nitride Nanosheets' Dosing

ABSTRACT

Poly(

‐lactic acid) (PLLA) has shortcomings, including slow crystallization and low heat resistance, which limit its practical application. Hexagonal boron nitride nanosheets (BNNSs) are well‐known for their superior heat conductivity and appropriate mechanical properties. BNNS was incorporated into PLLA by combining coprecipitation with press molding to investigate the influences of both BNNS's content and melt crystallization on the microstructure, crystallization, and performances of PLLA composites via characterizations such as DSC, WAXD, SEM, DMA, TGA, as well as mechanical and thermal conductivity tests. Results exhibited that BNNS reduced the size of spherulites and lifted the crystallinity of PLLA without changing the original crystal structure of α‐form PLLA. Crystallization of both PLLA and its composites benefited from melt crystallization at 95°C and 115°C for the more apparent nucleation effect from BNNS. BNNS strengthened the PLLA matrix, and suitable melt crystallization enhanced the mechanical strengthening effect by making the PLLA composites stronger as well as tougher. BNNS lifted T _g of the PLLA composites, and certain contents of BNNS entitled the composites with improved thermal conductivity, thermal decomposition temperature, as well as thermal resistance index. PLLA/BNNS composites crystallized under 95°C and 115°C displayed superior thermal resistance to other samples.