Shear induced crystallization, a relaxation phenomenon in polymer melts

Abstract

A survey is given of the experimental evidence of shear induced lamellar crystallization of polymers. This survey forms the basis for a theory by two of the authors. In this theory elements of polymer melt rheology and polymer crystallization kinetics are combined. In turns out that the capability of the melt of crystallizing in the typical lamellar form, is only gradually developed during flow. Similarly, relaxation occurs after cessation of flow. The obtained expressions are introduced into Avrami’s formalism in order to define an induction time. In principle the model can be applied to any flow and temperature history. The case of isothermal flow at constant shear rate and at a certain level of supercooling is worked out in more detail. The obtained result favorably compares with experiments by Lagasse and Maxwell. Implications for the application in industrial processes are discussed.