Non-isothermal crystallisation kinetics with instantaneous nucleation

The problem of the kinetics of non-isothermal crystallisation is analysed b oth from a theoretical and experimental point of view. The most common equa tions used to describe the kinetics of non-isothermal crystallisation-the N akamura and Ozawa equations-are analysed and discussed. The Nakamura equati on is re-derived without invoking the isokinetic condition, and it is shown that this equation is valid only for non-isothermal crystallisation with i nstantaneous nucleation. It is also shown that the Ozawa equation for pre-d etermined nucleation is incorrect. A Tobin-type equation for non-isothermal crystallisation with instantaneous nucleation is also derived. The experim ental problems related with the recording of data for this type of crystall isation 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 (time-dependen t) real sample temperature increase in nominally isothermal experiments was quantified. The isothermal process was then treated as a truly non-isother mal one, from the (low thermal conductivity) sample's standpoint. (C) 2000 Elsevier Science Ltd. All rights reserved.