Characterization and Thermal Degradation of Poly(d,l-Lactide-co-Glycolide) Composites with Nanofillers

Chemical and thermal characterization of poly(d,l-lactide-co-glycolide) (PLGA) composites filled with hydroxyapatite (HA) or carbon nanotubes (CNT) were evaluated by infrared spectroscopy, differential scanning calorimetry, thermogravimetry, and dynamic-mechanical-thermal analysis. The morphology and distribution of the nanoparticles were studied by transmission electron microscopy. The composites were prepared by solvent casting using 30% HA or 1, 3, and 5% of pristine and functionalized CNT as nanoparticles and PLGA 75: 25 and PLGA 50: 50 as copolymer matrix. The Coats-Redfern and E-2 function methodologies were used to calculate the reaction order and the activation energy (E-a) of the thermal degradation process. It was found that the addition of nanoparticles increased the glass transition temperature (T-g) of the composites. Also, higher degradation temperatures and E-a values were obtained for PLGA-HA composites and compared with the neat copolymer, and the opposite behavior was exhibited by PLGA-CNT composites. The thermal and mechanical properties were highly dependent on the morphology and dispersion of the filler. The functionalization process of CNT promoted, to some extent, a better distribution and dispersion of CNT into the matrix, and these composites exhibited a slight enhancement on storage modulus. On the other hand, PLGA-HA composites showed a good dispersion but no improvement on the storage modulus below T-g. (C) 2012 Society of Plastics Engineers