Three classical methods (Pseudo-Avrami, Ozawa, and Mo models) were used to correlate nonisothermal melt and cold crystallization kinetics data of neat poly(3-hydroxybutyrate) (PHB) and PHB/carbon black compounds, measured by differential scanning calorimetry. The applicability of the three models was tested comparing model predictions with experimental data. Results suggest that Pseudo-Avrami model fits the experimental data well. Ozawa model does not fit data well, as verified by the large uncertainties and unphysical values of the fitting parameters. Mo model may be considered adequate if moderately deviations could be tolerated. Datasets of all compositions are included as the Supplementary Information.

Compounds of poly(3-hydroxybutyrate) (PHB) and carbon black (CB) with CB content ranging between 0.5 and 10% were prepared in an internal mixer. The effect of heating and cooling rates on the crystallization and melting of PHB/CB compounds was investigated by differential scanning calorimetry (DSC), and its morphology analyzed by optical microscopy (OM). Results showed that PHB and its compounds partially crystallize from the melt during cooling and partially cold crystallize on reheating, with the amount of polymer crystallizing in each stage depending strongly on the cooling rate. Melting is usually shown in DSC scans as complex (double) peaks, which are influenced by the heating/reheating thermal cycles. The melting and cold crystallization temperatures, and the rates of phase change depend strongly on the cooling and heating rates and CB content. CB acts as a nucleating agent, promoting the melt and cold crystallization of PHB as well as increasing the number of spherulites, with a mild effect on the melting transition. Light microscopy images suggest that a secondary crystallization of PHB also occurs during storage at room temperature.