Thermodynamic analysis of two-dimensional crystal growth in nucleated isotactic polypropylene

A thermodynamic model is used to describe the two-dimensional crystallization kinetics ?as observed by means of a calorimeter? of polypropylene nucleated with small amounts of indigo. The customary expression of the free enthalpy associated to secondary nucleation is initially used to analyze the experimental data. A significant dependence of the apparent surface tension ?either basal or lateral? of the nuclei on the concentration of indigo is pointed out. To account for this effect, a phenomenological correction to the free enthalpy of nucleation is considered afterwards, which is connected with an entropy contribution arising from the formation of the crystal-melt interface. A more detailed data analysis is then carried out in light of this model.