Estimation of polymer nucleation and growth rates by overall DSC crystallization rates

Abstract

Isothermal crystallization of a polyoxymethylene copolymer in the temperature range of 423–429 K (150–156 °C) was performed using a differential scanning calorimeter (DSC) and data of crystalline development processed within the framework of a nucleation and growth model. Morphological investigations on DSC crystallized specimens were performed by scanning electron microscopy (SEM) and correlated to DSC data to obtain good estimations of spherulite growth rates in the explored temperature range. The accuracy of the growth rate has been enhanced by Hoffman regime analysis using reliable values of input parameters. Moreover, the function describing the number of growing spherulites as a function of time at constant temperature has been obtained. A method to evaluate both the growth rate and the number of spherulites effectively growing with time at constant temperature is shown for a polyoxymethylene copolymer (POMC). It consists in following the development of the crystallinity with time by differential scanning calorimetry and in estimating the maximum radial dimension of coalesced spherulites in the crystallized sample by scanning electron microscopy. The method is applicable to any linear polymer to obtain information on the nucleation and growth processes.