Gamma irradiation of melt processed biomedical PDLLA/HAP nanocomposites

• Biomedical polylactic acid/hydroxyapatite nanocomposites prepared by melt-compounding were gamma irradiated.
• Transmission electron microscopy showed hydroxyapatite nanoparticles evenly distributed within polylactic acid ranging from 10 to 100 nm.
• A halo appeared around hydroxyapatite particles showing interfacial interactions between polylactic acid and the particles.
• Double melting peak appeared for polylactic acid in DSC thermograms upon gamma irradiation of the nanocomposites.

Poly(d-l lactide) PDLLA/hydroxyapatite (HAP) nanocomposites at various compositions were prepared by melt-compounding process and then subjected to gamma irradiation at a dose of 30 kGy. The morphology of the nanocomposites, characterized by transmission electron microscopy (TEM), displayed HAP nanoparticles at various sizes ranging from 10 to 100 nm distributed almost evenly within the polymer matrix. Differential scanning calorimetric (DSC) analysis of the irradiated nanocomposites showed an increase in the degree of crystallinity along with a melting peak split. The double melting peak suggested formation of different crystalline structures in the radiation exposed nanocomposites. Also the cold crystallization peak shifted to lower temperatures and became much sharper upon irradiation, indicating higher crystallization rate. The irradiated nanocomposites showed lower tensile strength and elongation at break, suggesting occurrence of some chain scission reactions in the PLA.