POLY(STYRENE-GRAFT-ETHYLENE OXIDE) AS A COMPATIBILIZER IN POLYSTYRENEPOLYAMIDE BLENDS/

Polystyrene (PS) blends containing a dispersed phase of either polyami de-6 (PA-6) or polyamide-12 (PA-12) were compatibilized by additions o f 1, 3, or 5 wt % poly(styrene-graft-ethylene oxide). The graft copoly mers were found to have a stabilizing effect on the domain sizes. Weig ht average radii of PA-6 domains in compression molded samples were re duced by a factor of 5 with 3 wt % graft copolymer added. The correspo nding size reduction for PA-12 domains was by a factor of 3. Also, the domain sizes were more uniformly distributed in blends containing the graft copolymers. Thermal analysis of the blends revealed that compat ibilization retarded the PA crystallization, with some PA crystallizin g at the PS glass transition. This retarded crystallization is explain ed as a result of the domain size reduction and by the presence of gra ft copolymer at the interface. The graft copolymers had a toughening e ffect on the blends and the impact strength of a PS/PA-12 blend was im proved by 65% by adding 3 wt % of graft copolymer. Binary blends of th e PA and poly(ethylene oxide) (PEO) were investigated in a separate st udy to verify miscibility of the graft copolymer side chains and the P A. Hydrogen bonding between PA-6 and PEO was confirmed by IR spectrosc opy and partial miscibility was indicated by melting point depressions . (C) 1995 John Wiley & Sons, Inc.