Bi-cellular Foam Structure of Polystyrene from Extrusion Foaming Process

This article investigates the foaming process of bi-cellular polystyrene foams blown with n-butane and water in extrusion. The bi-cellular foam structure has two types of cells: large cells ranging from 0.1 to 1.2 mm and small cells ranging in size from about 5% to about 50% of the average large cell size, which constitute more than 90% of the total cell volume. A bi-cellular structure has outstanding heat insulation property. In order to generate a bi-cellular structure, a water-blowing technology was used. This technique is environmentally benign and economical since butane and water are used as blowing agents. Despite these advantages, the foaming process and mechanism of bi-cellular foams have not been identified in detail. Therefore, in this article, an attempt has been made to enhance our knowledge and understanding of the foaming behavior of bi-cellular polystyrene foam. The effects of n-butane, water, and silica (a nucleating agent) on the foam cell morphology are presented.