Photo-response of polylactide-poly(methyl methacrylate) blends: Effect of ultraviolet irradiation

The applications of biodegradable polylactide (PLA) are dependent on its structural durability under service conditions. In this work, we analyze the temperature dependence of photo-stability of polylactide-poly(methyl methacrylate) (PLA/PMMA) blends after the irradiation of ultraviolet (UV) light. X-ray diffraction analysis of the UV-irradiated PLA reveals the crystalline phase formation at 55 °C, as confirmed by thermal analysis. The UV irradiation decreases the crystallization temperature of PLA. The thermal analysis and Fourier Transform Infra-Red (FT-IR) analysis illustrate the interaction between PLA and PMMA. We evaluate the photo-stability of the UV-irradiated PLA/PMMA blends from the temporal evolution of optical absorbance/transmittance of the blends. A first-order kinetic analysis is used to analyze the change of optical absorbance, controlled by the annihilation and generation of color centers. Two processes contribute to the photo-stability of the PLA/PMMA blends – one is annihilation-dominant for the blends with a large fraction of PMMA, and the other is generation-dominant for the blends with a large fraction of PLA. The combinational effect of UV irradiation and the interaction between PLA and PMMA determines the photo-stability of PLA/PMMA blends.