Effects of UV-irradiation on the thermo-mechanical properties of optical grade poly(methyl methacrylate)

We studied the evolution of the thermo-mechanical properties of poly(methyl methacrylate) (PMMA) materials exposed to ultra-violet (UV) light. To do so we measured important mechanical parameters including the fracture strength, the stress-strain relation, and Young's modulus as a function of the UV-irradiation dose. We concluded that the mechanical properties of PMMA are affected by UV light. The ductility disappears and the strength and strain at rupture strongly decrease (over 30%). The evolution of the Young's modulus is discussed as a function of the cross-linking degree of the materials. Moreover we observed the occurrence of surface damage, which in its turn enhances the degradation of these mechanical parameters.