MISCIBILITY AND MECHANICAL-PROPERTIES OF A TERNARY POLYMER BLEND - POLYSTYRENE POLYCARBONATE TETRAMETHYL POLYCARBONATE

The phase behaviour and morphology of a ternary blend, consisting of polystyrene (PS), bisphenol A polycarbonate (PC) and tetramethyl bisphenol A polycarbonate (TMPC), are investigated by thermal and mechanical analysis and by transmission electron microscopy. It is shown that the TMPC, which is miscible with each of the other components of the blend, does not solubilize the two immiscible polymers, PS and PC. Two glass transitions are observed for most of the blend compositions. Single phases are obtained only at very high TMPC content. The interaction parameters for the three binary blends were obtained from the literature and utilized to calculate the spinodal for the ternary blend. The theoretical calculation agrees well with the experimental data. It is shown that the relative molecular weights of the polymers have a considerable effect on the phase diagram of the ternary blend.