Polypropylene/elastomer/poly(styrene-co-acrylonitrile) blends: Manifestation of the critical volume fraction of SAN in dynamic mechanical, tensile and impact properties

The effect of the critical volume fraction v^sub cr^ of poly(styrene-co-acrylonitrile) (SAN) on the mechanical properties of its blends with rubber-toughened polypropylene (RTPP) containing about 12% grafted ethylene-propylene copolymer was studied. To encompass a wide spectrum of mechanical properties, blend components were selected which are characterized with rather different viscoelastic, tensile and ultimate properties. The SAN volume fraction in blends covers the interval 00.30; concentration dependencies of measured mechanical properties indicate v^sub cr^ = 0.13. Experimental data on storage modulus E^sub b^', loss modulus E^sub b^'', tensile modulus E^sub b^, yield S^sub yb^ and tensile S^sub ub^ strength are in plausible accord with their simultaneous prediction based on a predictive scheme which operates with a two-parameter equivalent box model and the data on the phase continuity of components obtained from modified equations of the percolation theory. Strain at break, tensile energy to break and total impact energy of blends show a conspicuous drop in the interval 015 % of SAN where SAN forms a discontinuous component; further growth of the SAN fraction accounts for a reduction of the blend ultimate properties to the values typical of brittle polymers.[PUBLICATION ABSTRACT]