AbstractThe nonsteady flow behavior of a characterized commercial polystyrene has been examined in a compressed‐nitrogen‐gas piston viscometer. Nonsteady flow data were erratic with virgin polymer at 173.9°C. Pretreatment of the polystyrene by subjecting the melt to a higher temperature, with or without shear, changed the nature of the time‐dependent flow to that which is generally characteristic of polymers in experiments of this type. The pretreatment had no significant effect on the equilibrium flow curve at the same temperature nor on the molecular weight of the polystyrene. The results are interpreted in terms of changes in the size or nature of supermolecular flow
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