HIGH-TEMPERATURE PROPERTIES OF POLY(STYRENE-CO-ALKYLMALEIMIDE) FOAMS PREPARED BY HIGH INTERNAL PHASE EMULSION POLYMERIZATION

The influence of three N-substituted maleimides on the processing, the rmal, and mechanical performance of high internal phase emulsion (HIPE ) polymerized foams are investigated. N-propylmaleimide, N-butylmaleim ide, and N-cyclohexylmaleimide were copolymerized with styrene and cro sslinked with either divinylbenzene or bis(3-ethyl-5-methyl-4-maleimid e-phenyl)methane in a HIPE polymerization process. The foam samples we re evaluated by dynamic mechanical analysis, thermogravimetric analysi s, compression strength measurements, and scanning electron microscopy . All maleimide modifiers produced increases in the foam glass transit ion temperature (T-g) as a function of the maleimide concentration. Ho wever, the degree of T-g improvement was strongly dependent on the N-s ubstituted maleimide used during processing. Cyclohexylmaleimide produ ced higher T-g foams than propylmaleimide, which produced higher T-g f oams than butylmaleimide. In addition, the N-substituted maleimide sol ubility in both the oil and water phases played important roles in the processing and final open-celled microstructure. The preferred N-subs tituted maleimide modifier should possess high solubility in the oil p hase and insolubility in the water phase. (C) 1998 Published by Elsevi er Science Ltd. All rights reserved.