Study of thermal aging effect on space charge in poly(methyl methacrylate (original) (raw)
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Study of charge relaxations after thermal aging in poly (methyl methacrylate)
Physics Procedia, 2009
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 (ȕ, α and ȡ) have been highlighted by TSDC.
Polymer, 1999
A combined study of β′ and α relaxations in poly(methyl methacrylate) (PMMA) by thermally stimulated depolarization currents and thermal step methods has been made. The use of null width polarization windows to form the electrets allows us to isolate the β′ peak. The charge distribution profiles allow us to assign a polar orientational mechanism for the β′ relaxation and in the case of the α peak a background polar mechanism over which a temperature-dependent injection and a conduction processes are overlapped. The charge distribution profiles observed by the thermal step method indicate that the increase of the conductivity observed in this material at temperatures just below the glass transition is mainly due to the positive carriers.
In this work, thermally stimulated depolarization current (TSDC) and dielectric relaxation spectroscopy (DRS) techniques were performed in complementarities to characterize the dielectric relaxation processes in poly(methylmethacrylate) (PMMA) polymer. Three relaxations were highlighted. Based on correlation between TSDC and DRS data, theywere attributed respectively to dipolar β and α relaxations as well as interfacial ρ relaxation. New experimental procedure of fractional polarizationwas used to investigate space charge trap depth distribution within the band-gap of PMMA. Then the individual peaks were fitted to Bucci–Fieschi model, to evaluate the relaxation parameters. The obtained values were discussed in correlation to those evaluated from DRS data fitted to Havriliak–Negami and Arrhenius models. The various observed peaks in the thermograms are discussed on the basis of space charge polarization. The trap energies were evaluated from the fit to the Bucci–Fuschi model. Similarly other parameters such as relaxation time and charge release are evaluated.
Electrical ageing effects on dielectric properties of polymethyl methacrylate
The European Physical Journal Applied Physics, 2013
By combining the techniques of dielectric relaxation spectroscopy (DRS), measurement of both ac and dc conductivities, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), we have explored the effect of electrical ageing on poly (methyl methacrylate) (PMMA) films at temperature between 0 • C and 80 • C in the frequency range of 1 Hz-10 7 Hz. These results are discussed and correlated to FTIR and SEM observations.
Study of space charge relaxation in PMMA at high temperatures by dynamic electrical analysis
Polymer, 2001
Dynamic electrical analysis shows that at high temperatures (above the glass transition temperature), the electrical properties of polymethyl methacrylate are strongly influenced by space charge. In this paper we present an study of space charge in this material and its conductive properties by dynamic electrical analysis, using the electric modulus formalism. The complex part of the electric modulus was fitted to Coelho's model, which considers ohmic conductivity and diffusion as the prevailing mechanisms of charge transport.The complex part of the electric modulus exhibits a peak in the low frequency range that can be associated with space charge and a good agreement between experimental and calculated data is observed after the fitting process to the Coelho's model. The data obtained indicate that the electrode is partially blocked. The conductivity determined is thermally activated and it increases with the temperature due to an increasing mobility, that is also thermally activated.
Journal of Electrostatics, 2010
Poly(methyl methacrylate) Polyblends Thermally stimulated discharge current (TSDC) and transient currents in charging and discharging modes Curie-Von Schweilder Law Induced dipolar polarization Dipolar and space charge mechanism Plasticization effect a b s t r a c t The TSDC and transient currents measurement have been carried out on pure poly(vinyl chloride), poly (methyl methacrylate) and polyblends of various weight ratios as a function of electric fields at constant poling temperature. For PVC and different blend samples single peak in the temperature range 100e170 C has been observed in TSDC thermograms, however, for PMMA samples two peaks were observed at around 90 and 165 C. The various TSDC parameters i.e. activation energy, charge released and relaxation times have been calculated. Results suggest that dipolar and space charge mechanism are dominant for observed current.
Journal of Alloys and Compounds, 2009
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 • C and T min = 20 • 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.
Study of electrical properties of polymethylmethacrylate treated in aqueous and saline environments
Abstract. Polymethylmethacrylate (PMMA) is one of the most studied polymers in the last years due to its outstanding mechanical and physical-chemical properties. This material is used in various applications in which it can be subjected to different constraints. In this work, PMMA samples were submitted to thermal treatment (at 100 ◦ C for 20 min) in aqueous and saline environments. We studied the hydrothermal effect as well as the saline environment effect on electrical properties of PMMA by means of thermal step method (TSM) and thermally stimulated depolarization current (TSDC) technique. It was found that polarization was significantly influenced by the hydrothermal treatment realized particularly in a saline medium. α- and ρ-relaxations were observed in all TSDC spectra. For each treated sample, ρ-relaxation peak is more intensive than the dipolar one and the corresponding releasing charge quantity increases.
Thermostimulated depolarization currents in thermally aged polyethylene terephthalate (PET) films
Proceedings., Second International Conference on Properties and Applications of Dielectric Materials, 1988
Thermo-Stimulated Depolarization Current (TSDC) is used as a sensitive tool to probe residual space charge in insulations. However, quantitative information is difficult to extract as the response depends on the nature and position of trapped carriers. A model, developed to reproduce the behavior of space charge in a low-density polyethylene under electrical stress, is used to simulate the TSDC results. The model is one dimensional (sample thickness). Temperature effects have been introduced by using a hopping type of mobility, detrapping and charge injection also having temperature dependencies. Different parameters of the model are tested in order to evaluate their impact on the predicted TSDC spectrum.