Effect of TiO2 nanoparticles on the long-term hydrolytic degradation behavior of PLA

The longer-than-one-year hydrolytic degradation of poly (lactic acid) (PLA)/TiO2 nanocomposites was investigated in phosphate buffer solution of pH 7.4 at 37 °C so as to elucidate the effect of nanofillers on the degradation characteristics of PLA. The temporal changes in appearance, water absorption, number-average molecular weight (Mn), glass transition temperature, melting temperature, and crystallinity of the samples were traced. The results showed that the heterogeneous degradation and bulk-erosion were general mechanisms for PLA and its TiO2 nanocomposites. The change in surface morphology and molecular weight after hydrolysis revealed that the hydrolysis of nanocomposites occurred at the interface of PLA matrix and nanofillers, and the degradation rate was accelerated by the addition of the TiO2 nanofillers. The dispersion of nanofillers in polymer matrix affected the water absorption and degradation rate. The rapid increase of crystallinity also affected the degradation rate of nanocomposites. The present study suggested that the hydrolyzability of PLA could be controlled by adding TiO2 nanoparticles.