Polybutylene adipate terephthalate/polylactic acid interface enhanced compatibilization and its bead-foaming characteristics

Abstract

Bead foaming technique is regarded as a highly promising method for preparing foams with complex geometries and high expansion ratios. The biodegradability of poly(butylene adipate-co-terephthalate) (PBAT) has garnered significant attention in the field of foam materials. However, due to inherent disadvantages such as low melt strength and low modulus, PBAT faces challenges during bead foaming. In this study, a small amount of polylactic acid (PLA) was incorporated into PBAT. Utilizing the differential melting points of PLA and PBAT, PLA served as physical cross-linking points. The epoxy-based chain extender ADR4370S was used as a chain extender and compatibilizer. By varying its content, the compatibility and foaming performance of the PBAT/PLA blend were regulated. Finally, the foaming process employed supercritical carbon dioxide (scCO₂) impregnation followed by heating to address the hydrolysis issue of the PBAT/PLA blend during bead foaming. The results demonstrated that the introduction of ADR could initiate reactions between its epoxy groups and PBAT and PLA, resulting in grafting and chain extension. When the ADR content reached 0.6 wt%, the cell structure evolved from a bimodal to a uniform cell structure, with a minimum average cell size of 12.3 μm and a maximum foaming ratio of 10.3 times.

Keywords: ADR; Bead foaming; Cell control; PBAT foaming; Supercritical carbon dioxide foaming.