Delay in the growth of polymer spherulites caused by superheating

Heat transfer from a crystallizing substance to the surrounding is indispensable for the crystallization to proceed and therefore the deceleration of the growth front of spherulites, under conditions that prevent a rapid heat exchange, proves the existence of superheating phenomena in polymers. In this paper a method is shown to demonstrate the slow down of polymer spherulites as a consequence of superheating. The method consists in measuring the increase of the radius of spherulites while the external temperature is increased in the range where crystallization occurs. The experimental increase of a spherulite size is reduced with respect to the theoretically predictable enhancement of the size on the base of the isothermal growth rate data.