Migration of triacetin from polylactic acid/ethylene-vinyl acetate blend films

Abstract

Poly(lactic acid) (PLA) is a biodegradable polymer, but its brittleness limits its applications. A plasticizer is commonly used to improve the toughness of the PLA but the migration ability of the plasticizer is a concern. This study aims to investigate the migration of triacetin (TRI) as a plasticizer in PLA in the presence of ethylene-vinyl-acetate copolymer (EVA). PLA/EVA-Tri were prepared by melt blending process using an internal mixer. The plasticized PLA/EVA films were exposed to different environmental temperatures (60 °C, 70 °C, 80 °C and 100 °C) in an oven for 420 min to assess the migration of the plasticizer from the films into the air and to estimate activation energies. The film with 5% of TRI showed the lowest mass loss in general. The migration characteristics were compared with plasticized PLA. The migration rates of the TRI from PLA/EVA blend increased with increasing TRI content due to the higher diffusion coefficients in the polymer. Meanwhile, higher migration was found in plasticized PLA compared with plasticized blend at a similar amount of plasticizer based on the total weight of the sample. The activation energies of migration and diffusion coefficients both showed the same trend.