Effects of ultraviolet irradiation on the aging of the blends of poly (lactic acid) and poly (methyl methacrylate)

Abstract

Understanding the structural degradation of polymers and polymer-based materials is of practical importance in improving the reliability and lifespan of the associated structures and systems. In this work, we use differential scanning calorimetry to analyze the effect of ultraviolet (UV) irradiation on the physical aging of the blends of poly (lactic acid) (PLA) and poly (methyl methacrylate) (PMMA). Using the Cowie-Ferguson model and the Kohlrausch–Williams–Watts (KWW) stretch function, we determine the thermodynamic and kinetic contributions to the aging of the PLA/PMMA blends with and without UV irradiation. The analyses reveal the linear decrease of the maximum enthalpy loss of the aged specimen at the equilibrium state with the increase of the aging temperature, and the decreasing rate increases slightly with increasing the UV irradiation dose for the same PLA/PMMA blends. The activation energy associated with the kinetic contribution decreases with the UV irradiation dose for the PLA/PMMA blends of the same compositions. • UV irradiation has no effect on the relation between T g and composition of PLA/PMMA blends. • Increasing UV irradiation reduces the decreasing rate of the maximum enthalpy loss of aged PLA/PMMA blends. • Kinetic analysis of the kinetic contribution to physical aging of PLA/PMMA blends.