Chain extension of poly (butylene adipate-co-terephthalate) and its microcellular foaming behaviors

A facile chain extension and solid-phase batch foaming method was proposed to prepare microcellular poly (butylene adipate-co-terephthalate) (PBAT) foams in the presence of supercritical CO2. Branching structure and micro cross-linking structure were generated in modified PBAT with styrene-acrylonitrile-glycidyl methacrylate terpolymer (SAG) as chain extender, which was confirmed by Fourier transform infrared spectra, gel permeation chromatography and gel fraction measurements. The intrinsic viscosity and branching degree of modified PBAT increased as well as their viscoelasticity was improved respectively, with the SAG content increasing. The crystallization temperature and crystallinity of various PBAT samples increased and then decreased slightly due to the heterogeneous nucleation effect of branching points and the generation of cross-linking structure. An interesting complex cellular structure was observed in modified PBAT foams with the SAG content of 1 and 3 wt%, owing to the different rheological properties in branching molecular chain regions and linear molecular chain regions.