Investigation on electrical properties of thermally aged PMMA by combined use of FTIR and impedance spectroscopies

Effects of thermal aging on electric properties of polymethyl methacrylate (PMMA) polymer are reported in this paper. PMMA samples are submitted to Successive heat-cooling cycles (T-max = 45 degrees C and T-min = 20 degrees C) in the ambient air. Different complementary techniques are thus employed to investigate structural modifications, conduction processes and dielectric relaxations. These are the Fourier Transform Infra Red (FTIR) spectroscopy, impedance spectroscopy and current-voltage technique. Results are discussed in terms of FTIR bands intensities, relaxation frequencies and electrical conductivity. We demonstrated that thermal aging favors oxidation phenomenon. This causes an increase of free radicals leading to space charge amount increasing. PMMA polymer presents therefore a less insulating character. (C) 2008 Elsevier B.V. All rights reserved.