Thermal properties, phase morphology and stability of biodegradable PLA/PBSL/HAp composites

Blends/composites of poly(lactic acid) (PLA) with poly(butylene succinate-co-lactate) (PBSL) and hydroxyapatite (HAp) were successfully prepared by a conventional melt-mixing process. The thermal properties, phase morphology, crystal structure, and in vitro hydro-degradability of the prepared samples were characterized and compared. Thermogravimetric analysis confirmed that adding HAp increased the thermal stability of PLA/PBSL blends in both air and nitrogen environments. The activation energy for PLA thermal degradation increased with increasing HAp content in the samples. Scanning electron microscopy results showed that HAp was uniformly distributed within the composites. HAp also played a compatibilizer role for the PLA/PBSL blends, leading to evidently reduced size of dispersed PBSL domains. The Avrami crystallization analysis revealed that the n values of PLA in different samples ranged within 2.1-3.9, and the presence of HAp caused athermal nucleation process of PLA crystallization. The activation energy for non-isothermal crystallization of PLA decreased from 136 kJ/mol in neat state to 86 kJ/mol in PLA(70)/PBSL(30)/HAp(20 phr) composite. Melting behavior study revealed that the presence of HAp increased the original crystals stability of PLA in the composites. X-ray diffraction results confirmed that the crystal structures of PLA and PBSL remained in the blends and composites. Finally, in vitro hydrolytic degradation tests showed that the HAp addition facilitated the degradation of the prepared samples. (C) 2018 Elsevier Ltd. All rights reserved.