Nonisothermal Crystallization Kinetics of Poly(butylene succinate) and Poly(ethylene succinate)

Abstract

Much more attention has been directed to biodegradable polymers due to their potential applications in the fields related to environmental protection in the last two decades. According to the difference in preparation methods, biodegradable polymers can be classified into two types. One is the biosynthetic polymer, such as bacterial polyhydroxyalkanoates (PHAs). Among them poly(hydroxybutyrate) (PHB) is probably the most extensively studied biodegradable thermoplastic polymer. Ha et al. recently reviewed the miscibility, properties and biodegradability of blends containing either PHB or poly(3-hydroxybutyrate-cohydroxyvalerate). The other is the chemosynthetic polymer, such as the aliphatic polyesters. Poly(butylene succinate) (PBSU) and poly(ethylene succinate) (PES) are just two of them. The chemical structures of PBSU and PES are (–OCH2CH2CH2CH2O2CCH2CH2CO–)n and (–OCH2CH2O2CCH2CH2CO–)n, respectively. The crystal structure, crystallization and melting behaviour of PBSU have been reported in literature. Polymer blending is often performed in order to improve the physical properties and extend the application fields of PBSU. PBSU was found to be miscible with poly(vinylidene fluoride), poly(vinylidene chloride-co-vinyl chloride), poly(ethylene oxide) (PEO) and poly(vinyl phenol). On the other hand, PBSU was found to show no miscibility with PHB, poly(3hydroxybutyrate-co-hydroxyvalerate) and poly(-caprolactone). We also studied the subsequent melting behavior of PBSU crystallized nonisothermally from the melt. The crystal structure, crystallization behaviour and melting behaviour of PES have been reported in literature. The crystallization and morphology of PES in binary miscible blends of two crystalline polymers have also been reported recently, such as in PES/PHB and PES/PEO blends. We also studied the subsequent melting behavior of PES crystallized nonisothermally from the melt and the crystallization kinetics as well as subsequent melting behaviour of PES from the amorphous glassy state. Crystallinity is known to play an important role in the physical properties and biodegradability of biodegradable polymers. Meanwhile, the crystalline structure and morphology of semicrystalline polymers are also influenced greatly by the thermal history. Therefore, much more attention should be paid to the crystallization kinetics study since it affects not only the crystalline structure and morphology of semicrystalline polymers but also the final physical properties and biodegradability for the biodegradable polymers. However, to the best of our knowledge, the overall crystallization kinetics studies, especially the nonisothermal crystallization kinetics studies from the melt, of PBSU and PES have not been reported so far in literature. But it is essential to study the nonisothermal crystallization kinetics from the viewpoint of practical application because most polymer processing operations are carried out under nonisothermal conditions. In this note we reported our results on the nonisothermal crystallization kinetics of PBSU and PES from the melt by differential scanning calorimetry (DSC). It is expected that the results will be helpful for a better understanding of the relationship between structure and properties of PBSU and PES from the viewpoint of practical process.