In this work compounds of poly(3- hydroxybutyrate) (PHB) and carbon black (CB) with CB content ranging between 0.5% and 10.0% were prepared in a laboratory internal mixer. The effect of heating and cooling rates on the melt and cold crystallization of PHB/CB compounds was investigated by differential scanning calorimeter (DSC), and the dependence of the relative crystallinity with the heating/cooling rate at constant temperature was analyzed by the Ozawa model. The model fits the experimental data over limited ranges of temperatures. However, in our opinion, and despite of the the possible theoretical interpretation of the parameters, Ozawa model cannot be recommended due to the high dispersion of the predicted data.