Visco‐elastic properties related to the phase morphology of 60/40 PC/SAN blend

Stress relaxation and dynamic mechanical measurements have been performed on a 60/40 blend of polycarbonate of bisphenol A (PC) and poly (styrene‐co‐acrylonitrile) (SAN). This paper clearly demonstrates that the phase morphology of an immiscible co‐continuous polymer blend is an important parameter in determining visco‐elastic behavior. The dynamic mechanical properties are discussed in terms of the visco‐elastic form of a Kerner equation as a function of the reciprocal Chalkey parameter, which has been used to quantify the co‐continuous phase morphology. The effective volume fraction of the SAN phase has been found to decrease as the phase structure coarsens during annealing above T g of both SAN and PC. This is probably the result of phase break‐up and subsequent inclusion of SAN domains in the PC matrix during the coarsening process, which modifies the structure produced during melt compounding and injection molding.