Simultaneous evaluation of viscosity and retardation time in glassy polymers by a parallel-plate technique

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Abstract
In this work we describe a new experimental procedure for parallel‐plate rheometry of glassy polymers above the glass‐transition temperature range. This method has been used with an automated setup built by us which is linked to a HP‐86 desk computer. Both our experimental procedure and experimental setup allow us not only to determine the Newtonian viscosity in the wide 104–109 Pa s range, but also the evaluation of a kind of retardation time. This is related to the time that the sample needs to reach the viscous behavior. Moreover, this time can be identified with the retardation time corresponding to the effects of the entanglements in the polymer melt, at least for the two polymers investigated here: polycarbonate and polysulfone.