Acrylonitrile/Styrene/Acrylate Structural Rubber Latex Particles as Impact Modifier for SAN Copolymer

Rubber modification of styrene/acrylonitrile (SAN) copolymer has been carried out using acrylonitrile/styrene/acrylate (ASA) structural rubber latex copolymer particles with a rubbery acrylate core and a rigid SAN (30 wt% acrylonitrile, AN) graft shell. The melt flow and toughness of SAN copolymer have been investigated in relation to core composition and particle morphology. The results showed that incorporation of rubber particles increases the torque equilibrium of the SAN copolymer during the melt blending process. The lowest and highest torque values were obtained for the blend samples containing large core-shell and small hemispheric rubber particles, respectively. On the other hand, the highest impact toughness was observed for the blend sample containing ASA core-shell structured particles with P(BA-co-2EHA) core composition due to its lowest glass-rubber transition temperature (Tg). The TEM micrographs were indications of good dispersibility for the particles with raspberry and coreshell structures within the SAN matrix. Whereas, large particle agglomerates wereobserved for the blends containing hemispheric structural particles. Dynamic mechanical thermal analysis (DMTA) results showed that the blends with core-shell particles possess a higher maximum tan δ and lower tan δ-curve broadening when compared to blends containing rubber particles with other morphologies. A good dispersion state of core-shell rubber particles in the copolymer matrix resulted in a more homogeneous structure and a narrower tan δ curve.