Flow-induced crystallization in polymer melts: on the correlation between nucleation and specific work

Abstract

A new counting technique for nuclei, as found after short-term shearing, has been developed with the aid of the plate-and-plate rheometer Linkam CSS450. For the purpose this apparatus was modified by the introduction of complementary polarizing optics (a polarizer and a λ-plate). With the aid of this technique the density of nuclei could be determined in a new way. When these number densities are plotted against the applied specific work, satisfactory agreement is found with results, which have been obtained previously with a sliding glass plate rheometer. Nevertheless, the limits of validity of the diagrams had to be discussed. A transition from a dynamic description with the aid of the specific work to a purely kinematic description with the aid of the frequency of successful encounters cannot be overlooked. In fact, with increasing specific work the influences of temperature and (non-Newtonian) viscosity appear to fade away.