Polystyrene and polyester polyurethane elastomer blends compatibilized by SMA

Blends of polystyrene (PS) with polyester polyurethane elastomer (PU-es) were compatibilized by addition of poly(styrene-co-maleic anhydride) (SMA) containing 7 wt % of maleic anhydride. Binary nonreactive (PS/PU-es) blends, binary reactive (SMA/PU-es) blends, and ternary reactive blends (PS/SMA/PU-es) were prepared with 10 and 20 wt % of PU-es. The maleic anhydride content in the ternary reactive blends was varied through addition of different SMA amounts from 0.5 to 5 wt %. Polyurethane in the blends' vas crosslinked by using dicumyl peroxide or sulfur to improve its mechanical properties. The experimental processing conditions, such as temperature and rotor speed in an internal mixer, were analyzed before blend preparation by processing the individual polymers, PS and SMA, and the PS/PU-es nonreactive blend (90/10), to prevent the degradation of the polymer during melt mixing and to assure macroscopic homogeneity. The torque behavior during the mixture indicated a grafting copolymerization, which was responsible for the significant drop of the PU-es domain size in the glassy matrix, as observed by scanning electronic microscopy (SEM). The miscibility of the glassy matrix, which was shown to be dependent on the composition and the phase behavior of ternary blends, became very complex as the SMA concentration increased, as concluded from dynamical-mechanical analysis. Blends containing 20 wt % of PU-es presented an increase up to a factor of 2 in the deflection at break in relation to PS. (C) 2004 Wiley Periodicals, Inc.9352297230