RHEODILATOMETER FOR MOLTEN POLYMERS.

A new cone-plate rheometer has been constructed in order to measure torque-induced sample volume change as well as the usually measured total thrust F and torque M. Of particular importance for molten polymers are the time-dependent values generated by step shear strain or by step shear rate tests: the former when combined with shear stress data, can be used to eliminate infinite classes of otherwise a priori admissible constitutive equations. The evidence suggests that Lin's torque data are anomalous, as he himself believed. One possible explanation for the anomaly that should be considered arises from the unwanted coupling between thrust and torque signals which sometimes occurs with the Rheometrics System Four rheometer.