A Novel Stress-Induced Nucleation and Foaming Process and its Applications in Making Homogeneous Foams,Anisotropic Foams,and Multilayered Foams *

Abstract

A new foaming process is described whereby cell nucleation and growth are induced by applying mechanical, compressive stress to a polymer-gas solution in the rubbery state. As opposed to the conventional techniques, the stress- induced nucleation has a very short induction time and occurs at relatively lower temperatures, and foams with high cell density and small cells can be made by this method. And because of the control over the nucleation and cell growth events, selective foaming can be performed to give not only homogeneous foams but also specialty foams such as anisotropic foams and image foams. At high stress levels, cell coalescence leads to multilayered foams with or without cells in the polymeric layers, and with discontinuous gaps in-between the layers.