Catalytic degradation of polystyrene into styrene and a design of recyclable polystyrene with dispersed catalysts

Degradation of polystyrene into styrene, including monomer and dimer, was s tudied using various kinds of solid acids and bases as catalysts. It was fo und that solid bases were more effective catalysts than solid acids for the degradation of polystyrene into styrene. This was attributed to difference s in the degradation mechanisms of polystyrene over solid acids and bases. Among the solid bases employed, BaO was found to be the most effective cata lyst, and about 90 wt.% of polystyrene was converted into styrene when ther mally degraded polystyrene was admitted to BaO powder at 623 K. Polystyrene films with dispersed BaO powder were then prepared as a model o f a recyclable plastic using a twin-roller heated at 393 K; the amount of B aO dispersed was only 1 wt.% of the polystyrene films. More than 85 wt.% of the polystyrene films with dispersed BaO were converted into styrene by si mple thermal degradation at 623 K without assistance of other catalytic com pounds. The films were expanded into polystyrene foams with dispersed BaO u sing a gas absorption/evolution technique. Styrene could be recovered from these foams by heating them at 673 K. (C) 2000 Elsevier Science B.V. All ri ghts reserved.