Water-Blown Expandable Polystyrene. Improvement of the Compatibility of the Water Carrier with the Polystyrene Matrix by In Situ Grafting

摘要

The compatibility of starch with the polystyrene matrix in the synthesis of water-blown expandable polystyrene (WEPS) was improved by making use of maleic anhydride. The foam morphology on the contrary is significantly changed after pre-expansion as the content of maleic anhydride is increased. It has been found that starch is grafted during the polymerization with styrene-maleic anhydride copolymer. Partial immscibility of polystyrene matrix and styrene-maleic anhydride grafts formed at higher concentrations of maleic anhydride causes the agglomeration of starch. Consequently, water, as the blowing agent, cannot be finely dispersed in the matrix, which is the reason of the irregular foam morphology. Different methods for the improvement of the compatibilization are discussed.