Non-isothermal crystallisation kinetics with instantaneous nucleation

Abstract

The problem of the kinetics of non-isothermal crystallisation is analysed both from a theoretical and experimental point of view. The most common equations used to describe the kinetics of non-isothermal crystallisation—the Nakamura and Ozawa equations—are analysed and discussed. The Nakamura equation is re-derived without invoking the isokinetic condition, and it is shown that this equation is valid only for non-isothermal crystallisation with instantaneous nucleation. It is also shown that the Ozawa equation for pre-determined nucleation is incorrect. A Tobin-type equation for non-isothermal crystallisation with instantaneous nucleation is also derived. The experimental problems related with the recording of data for this type of crystallisation are also analysed and discussed. As a further test of the validity of the theoretical models, and as a justification for the use of isothermal crystallisation data to model non-isothermal processes, the (timedependent) real sample temperature increase in nominally isothermal experiments was quantified. The isothermal process was then treated as a truly non-isothermal one, from the (low thermal conductivity) sample’s standpoint.