VISCOELASTICITY OF SOME ENGINEERING PLASTICS ANALYZED WITH THE MODIFIED STRESS-OPTICAL RULE

The complex Young's modulus, E*(omega), and the complex strain-optical coefficient, O*(omega), of poly(ether sulfone) (PES), polysulfone (PSF), and polyetherimide (PEI), were measured over the frequency range 1 to 130 Hz. The data were analyzed with a modified stress-optical rule: The Young's modulus was decomposed into two complex functions, E*(G)(omega) and E*(R)(omega); the modified stress-optical coefficient, C-R and C-G, associated with the rubber (R) and glass (G) components, respectively, were determined. The results for six polymers, including polystyrene, poly(alpha-methyl styrene), and bisphenol A polycarbonate were compared with each other. One of the coefficients, C-R, equivalent to the stress-optical coefficient in melts, mainly depended on the way in which phenyl groups were connected to the chain. The other, C-G, was in the range of 20 to 40 Brewsters, and did not strongly depend on the details of polymer structure. The component function, E*(G)(omega), which was located in the glassy region and originated from the high glassy modulus, was almost the same in shape when plotted against omega with double logarithmic scales. The R component, E*(R)(omega), located al the long time end of the glass-to-rubber transition zone, was slightly sensitive to the molecular structure of polymers.