Low-shrinkage biodegradable PBST/PBS foams fabricated by microcellular foaming using CO2 & N2 as co-blowing agents

Abstract

Poly (butylene succinate-butylene terephthalate) (PBST) displays favorable foamability with the supercritical CO2 as the blowing agent, but the foams behave serious shrinkage behavior. In this work, a serious of fully biodegradable PBST/poly (butylene succinate) (PBS) microcellular foams with low volume shrinkage ratio were fabricated with the co-blowing agent of CO2 & N2. The presence of PBS can not only improve the rheological behavior, crystallization and mechanical properties to alleviate shrinkage process, but also play the role of nucleating agent to promote cell nucleation. With the increasing content of PBS, the cell size of the foam decreases from 25.0 μm to 7.03 μm, the cell density increases from 8.84×108 to 3.19×1010 cells/cm3 and the volume shrinkage ratio reduces from 62.10% to 47.81%. Furthermore, it is demonstrated that the introduction of N2 can inhabit the shrinkage behavior of PBST/PBS foams effectively. With the introduction of 12 MPa CO2 and 8 MPa N2, the volume expansion ratio of PBST/PBS10 microcellular foam can achieve 10.6-fold with good dimensional stability.