Thermal, rheological and microstructural characterisation of commercial biodegradable polyesters

Growing environmental concerns along with new regulations are forcing industries to seek renewable raw materials for their products. This work studies the thermo-rheological properties of commercial biodegradable polyesters: two polylactic acids (PLAs), a polycaprolactone (PCL) and a PLA/PCL blend. Comprehensive material characterization by means of thermogravimetry/differential thermal analysis (TG/DTA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), frequency sweep tests and polarized light microscopy was carried out. The results have shown that the material thermal/thermo-rheological properties and, therefore, its microstructure, are strongly dependent on its thermal history. This fact arises from the slow recrystallization kinetics shown by PLA. Interestingly, PCL may play the role of nucleating agent for the PLA crystallization, making it faster. This issue must be carefully considered so that a reliable material characterization is achieved.