Significantly enhanced crystallization of polylactide Ingeo 4032D by polyethylene ionomer

Abstract

Poly(lactic acid) (PLA) is the most important biopolymer material due to its excellent biocompatibility, biodegradability, and processability. However, its widespread applications were significantly limited by its low crystallization rate. While adding small molecule organic nucleating agents became a commonly used method in enhancing the crystallization rate, these nucleating agents generally suffer from limited solubility, which caused compromised nucleation efficiency and undesirable product appearance due to their precipitation onto the surface of the PLA products overtime. Here we report an efficient method for improving the PLA crystallization performance by using polyethylene (PE) ionomer as an additive in the PLA/TMC300 (an organic nucleating agent) nucleation/crystallization process. The added ionomer led to enhanced crystallization rate and reduced crystalline grain size. The resulting PLA from crystallization with TMC300 and ionomer showed reduced glass transition temperatures, reduced contact angles, and enhanced elastic modulus without compromising the impact strength and elongation at break. A possible mechanism was proposed for the remarkable synergistic effects of ionomer and TMC-300 in modifying the PLA crystallization process with the ionomer playing the roles of both plasticizer (enhanced PLA chain mobility and crystallization rate) and compatibilizer (enhanced dissolution and dispersion of TMC300 in the PLA matrix). This work offered a promising strategy for crystallization and modification of PLA materials.