Extrusion Foaming Behavior of PBT Resins

Abstract

An investigation of the foaming behavior of polybutylene terephthalate (PBT) resins in extrusion is performed. Commercial grades of PBT with different molecular weights and rheological characteristics are chosen. PBTs with a high temperature chemical blowing agent are extruded under different material and operational conditions (e.g., amount of blowing agent, set temperature at the die, screw RPM, etc.) to allow the understanding of the effects of those conditions on product characteristics. The foamed extrudates are analyzed for density, morphology, and crystallinity. It is shown that the foaming behavior and the foam quality of PBT are functions of the characteristic properties of the resins including rheological and crystallization behavior.