Melt and cold crystallization in a poly(3-hydroxybutyrate) poly(butylene adipate-co-terephthalate) blend

Melt and cold crystallization characteristics of poly(3-hydroxybutyrate) (PHB) and poly(butylene adipate-co-terephthalate) (PBAT), two biodegradable polyesters of current industrial interest, as well as a PHB/PBAT blend, were investigated by nonisothermal tests of differential scanning calorimetry over a range of cooling/heating rates ranging between 2 and 64 °C min⁻¹. Although more difficult to study the crystallization under isothermal conditions, the quantitative evaluation of nonisothermal crystallization is required to understand and model industrial processes, which are conducted under nonisothermal conditions. While PBAT crystallizes completely during cooling, PHB and the PHB/PBAT blend show incomplete crystallization from the melt, the process being completed during the reheating stage. Notwithstanding the different crystallization behavior, crystallinity levels and melting points of PHB, PBAT and the blend have virtually identical melt crystallization temperatures, due perhaps to differences in the nucleating efficiency of the stereoregular homopolymer PHB and the random copolymer PBAT. These findings may be of enough interest for process engineers designing and controlling operations.