On a nonexponential transformation equation for spherulitic crystallization

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Abstract
An equation has been derived for the development of crystallinity from heterogeneously nucleated spherulites which impinge with a small number of neighboring but randomly centered spherulites. The crystallization‐time dependence calculated from the equation conforms to an Avrami equation with initial fractional values for the n exponent, and the equation appears to be a better fit of the initial time dependence of the crystallization of polyethylene than the Avrami equation itself. It appears to account satisfactorily for the observation of fractional n values in the analysis of the crystallization curves of this polymer. The derivation of the equation only accounts for the impingement of spherulites in pairs and does not allow for multiple impingements. This limits its fit to less than the total primary crystallization. The effect on nonrandom centering of spherulites is discussed.