Existence of a sharply defined maximum relaxation time for monodisperse polystyrene

Abstract

Abstract Heretofore, the master stress relaxation curves of amorphous polymers could only be resolved by approximation methods into a continuous distribution of relaxation times. This is obviously not entirely satisfactory in all cases, e.g., for Maxwellian stress decay or if the Rouse distribution for the rubbery flow region were truly applicable. A new procedure (termed Procedure X) is proposed where is favourable cases the master stress relaxation modulus in the rubbery flow region can be resolved in to a discrete distribution of relaxation times, including a well defined maximum relaxation time. This procedure was applied to monodisperse and polydisperse polydisperse polystyrene, the latter of heterogeneity index 1.5. It appears that Procedure X gives resonably well defined values for at least the two highest relaxation times in these two cases.