Poly (ε‐caprolactone)/polybutylene adipate terephthalate/hydroxyapatite blend bionanocomposites: morphology–thermal degradation kinetics relationship

Abstract

Polycaprolactone/polybutylene adipate terephthalate blends (PCL/PBAT) (90/10, 75/25, and 50/50 wt/wt) containing 1, 3, and 5 phr hydroxyapatite (HA) nanoparticles were prepared using solvent-casting technique. Scanning electron microscopic studies confirmed a homogeneous morphology for the blends and nanocomposites. Some agglomeration can be recognized using energy-dispersive spectroscopy mapping in the blends containing 5 phr HA. The DSC results confirmed the presence of nanoparticles in each phase, particularly in the crystalline region, and wetting coefficient confirmed the localization of nanoparticles at the interface. Thermal stability and degradation kinetics were analyzed using thermogravimetric analysis (TGA). Based on the TGA results, a multi-step degradation process resulted in the blends and blend nanocomposites and the PCL/PBAT blends showed better thermal stability and exhibited higher T_max and residual mass. PCL/PBAT blends were more stable at higher temperatures compared to PCL and PBAT. Various kinetics evaluation techniques, including Friedman, Flynn–Ozawa–Wall, and Kissinger–Akahira–Sunose methods, were utilized to determine the activation energy of degradation. PCL/PBAT blends were more difficult to thermally degrade and showed the highest degradation activation energy. Incorporating HA led to lower thermal stability and, therefore, lower degradation activation energy. Incorporation of only 5 phr of HA resulted in greater thermal stability at higher temperatures (T_90%).