Vapor-induced depolarization currents. II. Application (original) (raw)
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Vapor-induced depolarization currents in electrets
Journal of Polymer Science: Polymer Physics Edition, 1979
The charge decay of polymer electrets in the presence of solvent vapor is analyzed. In order to account for this phenomenon, several hypotheses are considered and tested experimentally. It is shown that the penetration of the solvent is responsible for the observed charge decay, and that it is the rate limiting factor. Moreover, the phenomenon is not due to the screening of the injected charges, but to the motion of these charges, which are liberated by the penetration of the solvent. Finally, the possible applications of this phenomenon in investigations on both the microscopic and macroscopic scale are outlined.
Solid Dielectrics (ICSD …
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.
Influence of physical aging on the performance of corona-charged amorphous polymer electrets
Journal of Polymer Science Part B: Polymer Physics, 2010
The influence of physical aging on the electret properties before corona charging of three amorphous polymers, polyetherimide (PEI), poly(phenylene ether) (PPE), and polystyrene (PS), as well as with blends of PPE and PS, was investigated. The degree of aging was monitored by determining the enthalpy relaxation Dh using differential scanning calorimetry (DSC). The electret performance was evaluated by isothermal potential decay (ITPD) at elevated temperatures and by thermal stimulated discharge (TSD) measurements. It was demonstrated that physical aging below the glass transition temperature substantially improves the electret performance of amorphous polymers by reducing the free volume and thus hindering charge motion. As an example, the performance of nonaged PEI was improved by physical aging at 200 C for 4 days from 18 to 95% retained charge after 24 h at 120 C. A similar beneficial influence of physical aging on the charge storage capability was achieved using blends of PPE with PS. V
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.
Corona-charged polypropylene electrets analyzed by XPS
Journal of Electrostatics, 2007
In the present study, we use X-ray photoelectron spectroscopy (XPS) analysis to clarify how different polarities of corona initiate various changes in the surfaces of polypropylene (PP) electrets subject to corona discharge. The samples were charged in three-electrode corona discharge system using positive and negative corona polarities at both À20 and 75 1C temperatures. The tests were divided into four groups. The surface potentials of the electret samples were measured using the vibrating electrode method with compensation. XPS studies were carried out by means of a VG ESCALAB Mk II electronic spectrometer using an Al Ka excitation source (hn ¼ 1486.6 eV). The spectra of C1s, O1s and N1s lines for all groups and for untreated samples were recorded and analyzed. The investigations that we carried out show that for negative-corona-charged samples, the oxygen content is approximately 2.4 times higher than that in positivecorona-charged samples. Based on the results we have obtained, we may assume that the changes in oxygen content in samples charged by different polarity coronas lead to the formation of different surface local levels. This assumption agrees well with the experimental measurement made on the electrets. r
Thermally Stimulated Depolarization Studies of PVC Polymer Electrets
Journal of The Electrochemical Society, 1978
Thermally stimulated depolarization of cellulose nitrate has been measured as a function of polarizing voltage, electret forming temperature, heating rate and storage time. A single peak due to polar side ester group is observed at approximately 50°C, whose magnitude increases with polarizing voltage. The peak is absent for low (5 90°C) and high (2 140°C) electret forming temperatures. In the intermediate temperature range the value oE the peak current decreases with the forming temperature from 100 to 120°C and then increases. The magnitude of the peak current and the peak temperature increase with heating rate and decrease with storage timc. Untersuchungen zur thermisch stimulierten Depolarisation von Cellulosenitrat Die thermisch stimulierte Depolarisation van Cellulosenitrat wurde in hbhangigkeit van der Polarisicrungsspannung, der Polarisierungstemperatur, der Aufheizgeschwindig~cit und der Lagerzeit gemessen. Ein Maximum, das auf die polare Estergruppe zuriickzufuhren ist und dessen IIohe mit dcr Polarisierungsspaiinuiig zunimmt, wird bei ctwa 50OC beobachtet. Das Maximum tritt bei niedrigen (5 90°C) und hohen (2 140°C) Polarisierungstemperaturcn nicht auf. Im dazwischen liegenden Temperaturbereieh nirnmt dcr maximalc Strom van 100 bis 120°C a b und steigt danach wieder an. Hohe und Temperaturlage des Maximums nehmcn mit dcr steigenden Aufheizgeschwii~diglieit zu und mit der Lagerzeit ab. Bccfiedosanuz mepauuecEu UnayyuposannoiL aenofizpu3ayuu Mumpama yefifimnoabr H TeMnepaTypM nonxpm3qan~i, OT C K O~O C T M HarpesaHm H BpeMeHyr xpaHema. n p~i TeMnepaType = 5OoC ~a6n1on o n a p n 3 a q n o~~o r o HanpnxfeHHa. n p~ H H~K H X (5 90°C) II Bbicomx (2 140°C) TeMnepaTypax n o~~a p r n a a q~n l'I3MepeHa TepMHYeCKH HHAYqHPOBaHHaR AeIIOJIHpH3aqHR HHTpaTa qeJIJIIoJIO3bI B 3aBMCHMOCTH OT HanpRmeHHR
Thermally stimulated depolarization currents in natural beryl
Radiation Effects and Defects in Solids, 1995
The purpose of this study is an investigation upstream of polymer insulator ageing and rupture. We studied the electrical and physicochemical properties of a low-density polyethylene (LDPE) used in high-power insulated cables. Space charge measurements using pulsed electroacoustic method and thermally stimulated depolarization current (TSDC) were carried out on LDPE samples, with and without antioxidant, at different temperatures. TSDC peaks were observed only in the presence of an anti-oxidant. Furthermore, a TSDC anomalous peak was revealed for the sample containing an antioxidant and polarized at 508C. All the TSDC peaks are interpreted as trapped charges and can be explained by measuring the space charge distribution within the sample bulk.
Analyses of Behaviour of PP Corona Electrets Stored at Low Pressure
2010
Polypropylene electrets 20 μm thick charged in a negative corona were studied. The samples were charged to different initial surface potentials and were stored under various pressures for 30 minutes. Then, the surface potential was again measured. The dependence of the electret surface potential on the pressure, under which the electrets were kept after charging, was investigated. As the pressure was lowered from 1000 mbar to 0.1 mbar a sharp decay of the surface potential occurred. It was established that a main parameter determining the surface potential decay is the ratio of the pressure to initial surface potential, and only one generalized curve describes all results obtained. Analyses of the equation described the results obtained was done.
Thermally stimulated depolarization current studies of sulfonated polystyrene ionomers
Applied Physics A, 2009
Thermally stimulated depolarization current (TSDC) studies have been carried out on blends of polycarbonate (PC) and poly (p-t-butyl phenolformaldehyde) (PTBF) using electric poling at temperatures ranging from 348'K to 383°K. The PC/PTBF blends poled at identical electric field (E,) and temperature (T,) exhibit a continuous distribution of polarizability (in general, in the range 300°K to 450°K) with a blend composition dependent single peak (TM). With increasing Ep and T p , the TSDC peak of a blend shifts toward higher temperature with increasing peak current (1,) and charge (Q) associated with the peak. The effects of polarization field and temperature indicate that the polarization in the blend system is due to induced dipole formation. The activation energy decreases with increasing PTBF content in the blend, indicating shallow traps in PC/PTBF electret. The present blend electrets, however, comparative to its two components PC and PTBF, store more charge but decay faster. 0 1994 John Wiley & Sons, Inc.
Journal of Polymer Science Part B-polymer Physics, 2003
With thermally stimulated depolarization currents, we researched the relaxations of crosslinked polyethylene as it is used in medium-voltage cable insulation. Through conventional polarization two heteropolar peaks stand up in the spectra, at 80 and 105 °C. As the sample is annealed, a homopolar peak is developed at about 99 °C. With window polarization, our results indicated that the 80 °C peak is a structured peak related to polar crosslinking subproducts and impurities. The 105 and 99 °C peaks are fitted to the general kinetic-order model because the 105 °C peak is related to free-charge detrapping at the crystalline phase, in the bulk and maybe at the amorphous-crystal interphases, and the peak that is observed at 99 °C is due to injected charge. Annealing at high temperatures promotes the creation of traps in the material. Charge trapping at T < 70 °C seems to be related to the increased insulator resistivity with annealing time. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1412–1421, 2003