Effect of bioactive glass particles on the thermal degradation behaviour of medical polyesters

The thermal degradation behaviour of poly(ε-caprolactone) (PCL), poly(l-lactide) (PLLA) and poly(lactide/ε-caprolactone) (PLCL) and of composites of these polymers filled with bioglass particles was investigated by means of thermogravimetric analysis (TGA). According to the activation energies calculated by the Friedman approach, PCL showed the highest resistance to thermal degradation. Addition of bioglass induced a reaction between the ester groups of the polyesters and the SiO− groups present in the surface of bioglass particles which caused a 1.3-1.9 fold decrease in activation energies of the composites with respect to their unfilled polymer counterparts. This reaction was proven by the increase in the absorbance of the carboxylate peak in the infrared spectra of the composite films maintained at 210 °C and confirmed the random chain scission of the polymer chains. This fact caused a significant decrease in the featured thermal transitions of the polymers as determined by the differential scanning calorimetry (DSC) measurements.