Combined Effects of Saturation Pressure and Gas Desorption on Foaming Characteristics of Microcellular Plastics

Abstract

The microcellular foaming process consists of the saturation process for dissolving gas molecules into plastic and the subsequent foaming process for cell formation. Foaming characteristics of microcellular plastics (MCPs) such as foaming ratio and cell morphology are largely determined by the saturation conditions, particularly by the saturation pressure. In this study, we investigate the effects of saturation pressure on the foaming characteristics of MCPs, when the quantity of dissolved gas (or the weight gain) is kept constant. Because the weight gain of a specimen is an increasing function of saturation pressure, different desorption times are used in order to maintain the same weight gain across specimens from different saturation pressures. Contrary to the common belief, for specimens with the same weight gain higher saturation pressures lead to lower foaming ratios. A hypothesis for the underlying mechanism and a practical ramification of the phenomenon are discussed.

Keywords:

• Cell morphologies
• Gas desorption
• Saturation pressure
• Weight gain