1994 Volume 43 Issue 495 Pages 1546-1552
The complex Young's modulus, E*(ω), and the complex strain-optical coefficient, O*(ω), of a polystyrene (PS)/bisphenol A polycarbonate (PC) blend and a graft copolymer were studied in the glass-to-rubber transition zone at frequencies ranging from 1 to 130Hz at various temperatures between 102°C and 182°C. The relaxation behaviors in E*(ω) and O*(ω) of two alloys were compared with each other in relation to the relaxation behaviors of constituents, PS and PC. It was clarified that for the blend in the mechanical spectrum two isolated relaxation peaks are detected at frequencies apart from each other, which means that the consitituents relax independently. For the copolymer two relaxation peaks of constituents were almost merged giving rise to about a single peak which indicates cooperating relaxation of the two components.
The optical relaxation spectra, O*(ω), of two alloys showed distinct difference in quality and it also made us predict their compatibility to some extent. For both alloys, the stress-optical coefficient, CR, in the rubbery zone was reduced to 1/4-1/6 of the absolute value of components polymer as a result of compensation of the opposite-signed birefringences of constituent polymers. The photoelastic coefficient, Cd, for two alloys and the component polymers, PS and PC, exhibited a strong correlation with the stress-optical coefficient, CR.