The turning point on plots of log φ and log t of Mo's equation

Background: Mo's equation based on the Avrami equation and Ozawa equation has been successfully used in non-isothermal crystallization kinetics by many researchers. However, in recent years we have found that plots of log φ-log t of Mo's equation are not straight lines, but there appears a turning point at φ = 7°C min^-1 or so. The aim of this article is to analyze in detail the reason for the occurrence of this turning point by studying the non-isothermal crystallization of poly(vinylidene fluoride) (PVDF) using differential scanning calorimetry. Results: A turning point at about 7°C min^-1 appeared on plots of log φ -log t. The cooling rate where the turning point occurred showed little change with increasing relative crystallinity, but the temperature decreased. It is noted that this turning-point temperature is lower than transition temperature of regime I → II reported for PVDF. Conclusion: We deemed that the occurrence of turning points on plots of log φ-log t of Mo's equation can be ascribed to the different crystallization regimes based on the Hoffman nucleation theory, and presumed that the turning point corresponded to transition of regime I → II. Finally, we considered that Mo's equation should be analyzed using two beelines, instead of one beeline.