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Abstract: Effects of thermal aging on physico–chemical and electrical properties of polymethyl methacrylate (PMMA) are reported in this paper. PMMA samples are submitted to successive heat–cooling cycles (Tmin=20 ∘C and Tmax=90 ∘C) in the ambient air, each cycle lasts 12h. Different techniques are thus employed to investigate structural modifications, dielectric relaxations and conduction processes. These are the Fourier Transform Infrared (FTIR) spectroscopy, thermal step method (TSM), thermally stimulated depolarization currents (TSDC), dielectric spectroscopy (DS) and current–voltage technique. Results are discussed and a relationship between structural modifications and charge relaxations was emphasized. We demonstrated that thermal aging favors oxidation phenomenon. Three distinguishable charge relaxations (, and ) have been highlighted by TSDC. [Copyright &y& Elsevier]

Abstract: Charges evolution in poly(methyl methacrylate) (PMMA) samples under thermal aging effect has been studied by means of two complementary techniques, thermal step method (TSM) and thermally stimulated depolarization current (TSDC). For the first method, measurements reveal that injected charges, whose quantity is found depending on the number of applied temperature cycles, remain close to the surface sample. TSDC measurements have been carried out for different temperatures ranging from 25°C to 140°C. Three distinguishable dipolar relaxations (β 1 , β 2 and α) have been highlighted. In the same way, the presence of polarization and injected charges has been confirmed. In support of electric characterization, X-ray reflectometry has been used. The obtained results equally emphasized the thermal aging effect on the material. [Copyright &y& Elsevier]