PHASE MORPHOLOGY CHARACTERIZATION AND ULTIMATE MECHANICAL-PROPERTIES OF 60/40 PC/SAN BLEND - INFLUENCE OF THE ACRYLONITRILE CONTENT OF SAN

The tensile stress-strain properties of blends having a 60/40 weight ratio of polycarbonate of bisphenol-A (PC) and styrene-acrylonitrile copolymers (SAN) have been investigated for a range of SAN copolymers with different AN levels. It is clearly demonstrated that the phase morphology of these blends and the acrylonitrile (AN) content of the SAN component are important factors with respect to the ultimate mechanical properties (tensile strength and elongation at fracture). Following injection molding, a very fine phase distribution is observed for blends with SAN components containing 15 to 29% AN. By annealing of the blends at 200-degrees-C. i.e. above T(g)(PC), it has been possible to obtain different degrees of domain sizes. From this range of morphologies, quite similar phase structures can be selected differing only in AN-content of the SAN blend components. This allows a systematic investigation of the effect of the AN-content on the tensile stress-strain properties of PC/SAN blends. The elongation at fracture exhibits an optimum for blends with SAN containing 24% AN. A coarsening of the phase morphology only results in a decrease of the ductility and not in a shift of the optimum. The maximum tensile stress exhibits a sigmoidal trend as a function of the AN-content. This parameter remains constant for a typical PC/SAN blend with different morphologies.