Some Effects of Crosslinking Upon the Foaming Behavior of Heat Plastified Polystyrene

Abstract

Crosslinking of polystyrene containing blowing agents has a large effect upon foam ing behavior at elevated temperatures. The foam volume and resistance to thermal col lapse are both greatly increased by lightly crosslinking the polymer. If the crosslink density is too high, however, expansion is re stricted and foam stability decreases. The foaming behavior of a series of styrene-di vinyl benzene copolymers impregnated with carbon dioxide has been studied in detail at temperatures from 100 to 200°C. An at tempt has been made to correlate the in ternal pressures at maximum expansion with the theoretical elastic retractive forces of the copol ymer networks. A mechanism for ther mocollapse of polystyrene foams is proposed.