Lamellar Growth in Melt-Crystallizing Polymers: Some Effect Related to a Nucleating Agent

Abstract

The influence of a nucleating agent on the free growth kinetics and on the final average thickness of lamellae grown from melts in isothermal conditions is considered. The growth kinetics in isotactic polypropylene, high density polyethylene and polyethylene oxide, is observed by means of calorimetry, whereas information on the long period and lamellar thickness at crystallization completed is drawn from SAXS measurements (on polyethylene oxide only). Both the observations are analyzed in terms of a decrease of the lamellar basal surface tension associated to the accumulation of the nucleant at the interface. This decrease is also discussed by means of a simple lattice model, where a finite compressibility of the system is accounted for. In light of the assumed mechanism, kinetic and morphological observations are interpreted consistently.