Water-blown Expandable Polystyrene. Improvement of the Compatibility of the Water Carrier with the Polystyrene Matrix by in Situ Grafting

In the synthesis of water-blown expandable polystyrene, granular starch as a carrier of water, the blowing agent, was grafted with polystyrene by radical initiated polymerization. Organic peroxides, such as tertbutyl perbenzoate or dibenzoyl peroxide were used as free radical initiators. The graft polymerization reaction was confirmed by FT-IR spectroscopy and SEM. The reaction leads to low level grafted starch. However, the amount of grafted polymer can be significantly increased using maleic anhydride in the monomer feed. The effect of concentration of maleic anhydride was studied. The reaction mechanism was proposed.