Stretching-induced foaming of gas-laden thermoplastic elastomers

Abstract

Stretching-induced foaming of gas-laden thermoplastic elastomer (TPE), styrene-isobutylene-styrene (SIBS), was successfully conducted. CO₂-laden TPE plates were prepared by an injection molding process without foaming and later foamed by stretching. The effects of CO₂ concentration in the gas-laden elastomer, stretching rate (strain rate), and strain on bubble (cell) diameter and bubble density of the resulting foams were investigated, and a new bubble nucleation rate model was proposed to reflect the stretching effect on bubble nucleation in foam. The model has the stretching rate-dependent elastic strain energy in the bubble nucleation rate to explain why the higher stretching rate and the higher strain produce more bubbles of smaller size. The proposed bubble nucleation model clarifies the effect of the elastic modulus of TPE on the bubble nucleation barrier.