Studies on the influence of physical aging processes on electret properties of amorphous poly(methyl methacrylate)

Abstract

The influence of physical aging processes on the electret properties of amorphous poly(methyl methacrylate) was investigated. The experimental method of choice was the thermally stimulated discharge (TSD) technique. The result of these studies is that aging influences the magnitude of the electrical polarization within the glassy state and the thermal stability of the polarization originating from the frozen-in dipole orientation and from trapped charges. The effects of aging on electret properties can, to a good approximation, be accounted for on the basis of the phenomenological aging theory, as proposed by Kovacs et al. More detailed information on the relation between relaxation properties and aging of electret properties can be obtained from an analysis of the experimental results, based on the universal law approach, as proposed by Ngai et al.

Correlation between dipolar TSDC and AC dielectric spectroscopy at the PVDF glass transition

“…The value obtained thermal history of the samples is changed by varying the cooling rate. The most significant result for x 2 , the sum of the squared residuals, which indicates the goodness of the fitting procedure, is in these experiments is that to obtain a similar aging effect as that reported by Kubon et al 4 the 1.0 1 10 07 for the TSDC curve normalized 14 to a polarization equal to 1, or x 2 Å 3.7 1 10 031 V…”

“…ple's structural relaxation during TSDC measurements around the glass transition. Kubon et al 4 performed TSDC experiments in PMMA samples SADSA Analysis of the TSDC Peak aged 1000 h at T g -15 K, and they report a 5 K shift of the peak maximum to higher temperatures. To…”

“…This quency domain, the equivalent frequency of TSDC problem has been treated in two rather similar spans 10 03°f eq°1 0 02 Hz. As a result of this approaches by Schrader and Schönhals 3 and by lower working frequency in TSDC, the relaxation Kubon et al, 4 both analysis being only able to peaks are located at lower temperatures. This difdescribe qualitatively the evolution of the TSDC ference is particularly important when studying spectra.…”

“…number of the overlapping relaxations. Both DSA and SADSA methods are very precise tools to obKubon et al 4 have shown that the depolarization process in TSDC experiments is strongly influtain accurate descriptions of the complex relaxation kinetics found in polymeric materials. [18][19][20][21] enced by annealing treatments, when the annealing periods are long compared to the usual heatThe exact relationship between AC DS and the TSDC experiments has been sparsely investiing rates: t ann ӷ 1 h at T ann É T g 0 15 K.…”

Optical properties of ZnO/PMMA nanocomposite films

“…As it is known from the thermally stimulated discharge data in PMMA at the 220-230 K the relaxation processes causing a partial orientational relaxation of dipoles take place. The dipoles of the polar ester side groups (-COOCH 3 ) reorient by local motion around the C-C bond [12,13]. The nature of the "green" band is connected with the deep centers of emission caused by zinc V Zn [14,15] and oxygen vacancies V O [16,17] and interstitial atoms of zinc (Zn i ) [18].…”