Some electrical properties of thin films of polypropylene formed by vacuum evaporation (original) (raw)
Properties and Applications of Polymer Dielectrics, 2017
In this chapter, a comprehensive study on the general structure of polymers, their properties and applications has been carried out. In particular, the application of polymers for insulating high-voltage (HV) equipment has been reported, together with the effect of electric field when they are subjected to HV stress. Experimental results related to the effect of partial discharge (PD) on polymeric insulations have been reported and discussed. Practical implications of the results have been discussed, and recommendations are made for future improvement. It is important to obtain new information regarding novel polymeric materials such as nano-polymers that can possibly outperform the currently used ones. It is also vital to investigate the right information for electrical equipment, i.e. by using the appropriate polymer as solid insulation, minimizing the presence of any metallic sharp object and any other conducting path during manufacture in order to avoid any type of internal or external PD.
Thermally stimulated discharge conductivity in polymer composite thin films
Bulletin of Materials Science, 2006
This paper describes the results of thermally stimulated discharge conductivity study of activated charcoal-polyvinyl chloride (PVC) thin film thermoelectrets. TSDC has been carried out in the temperature range 308-400°°K and at four different polarizing fields. Results are discussed on the basis of mobility of activated charcoal and polyvinyl chloride chains.
Thermally stimulated discharge conductivity of PVC thin film
2002
Th e co nducti vit y and th erm all y stimul ated di scharge current s (TSOC) in polyv in yl chl orid e (PVC) are stu died in virgin and elec tr et thin fi lm sa mpl es. The V-I charac teri sti cs of th e film s at different temperatures reveal that th ere are th ree di stin ct reg ions. namely ohmi c, square la w and power reg ions. In th e squ are law region, space charge limit ed co nducti on is observe d. The possibility of Poole-Fre nk el or Ri chard so n-Sc hottk y mec han ism is also stu died. The fi eld -lowerin g coe ffi cient (B) is ca lculat ed. The Ri chard so n-S chottk y mec hani sm is observed. From - log (J VS . 1fT pl ot. th e ac ti va tion energy is es timat ed. The e lec tr ica l conducti vit y is found to in crease with decreasin g thi ckn ess. TSOC and condu cti vi ty are measured in th e film of elec trets in 3 13-333 K. Sin gle relaxa ti on peak is obse rve d in th e di sc harge curre nt vs. temperature plot whic h is du e to ro tati on of dipolar group at pea...
Relaxation phenomena and electrical conductivity of some polymeric films
European Polymer Journal, 1982
Electrical conduction in sandwich samples of polyacrylonitrile (PAN) or copolymer of acrylonitrile with butadiene between silver has been studied, measuring the dependence of current on the applied field, temperature and time. The conduction mechanism depends on the polymer type. A polarization contribution is suggested in the conduction mechanism at high temperatures, besides Schottky emission in the case of PAN and the simple carrier jump model in the case of NBR at room temperature. The temporal current variation is explained in terms of dipole orientation. The mobility and charge carrier density are influenced by the applied field, temperature and film thickness.
Surface and Coatings Technology, 2007
Plasma treatment of polymers is gaining more and more popularity as a surface modification technique, since it offers numerous advantages over the conventional chemical processes. Plasma surface treatment is an environmentally benign, fast and versatile technology. However, it has one major disadvantage: the induced modification of the surface is not permanent, since the surface tends to recover to the untreated state. This ageing effect is due to the reorientation of induced polar chemical groups into the bulk of the material. In this paper, the ageing of polypropylene (PP) and polyethylene terephthalate (PET) films, treated with a dielectric barrier discharge operating at medium pressure (5.0 kPa) in air, helium and argon, is studied. This study is performed using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Results show that the working gas used during plasma treatment has a significant influence on the ageing behaviour of both PP and PET films. The air-, helium-and argon-plasma treated PP films have a loss in treatment efficiency of 47%, 35% and 25% respectively, while the air-, helium-and argon-plasma treated PET films have a loss in treatment efficiency of 39%, 34% and 29% respectively. These results can be explained by the different crosslinking degrees of the polymer films after plasma treatment. Increasing the cross-linking degree will hinder the movement of the polymer chains and reduce the ageing effect.
Thermally stimulated discharge currents from pyrene-doped polystyrene films
Thin Solid Films, 1982
Pyrene was mixed with polystyrene (PS) in different molar concentrations in the range 0.2-12 mol.% and thermally stimulated discharge (TSD) current spectra of the doped PS films were studied for various dopant concentrations, polarizing fields and forming temperatures. Unpolarized films were observed to give a peak at 95 °C. The TSD current peak in the main relaxation region of PS shifts to the lower temperature side of the spectrum with increasing concentration of the dopant. The strong dependence of space charge polarization on the dopant concentration and the forming temperature IS assigned to an increase in the conductivity of the polymer.
Electrical conduction processes in polyimide films-I
IEEE Transactions on Dielectrics and Electrical Insulation, 2008
Extensive investigations of the absorption and desorption currents are carried out over the temperature range of 50 to 200 o C and electric fields up to 12 MV/m in 25.5 μm polyimide film base with 12.7 μm coating of Teflon ® FEP on one side. It is believed that this is the first time that studies on this film are reported in the literature.
Electrical Properties of Polyethylene Polypropylene
In high-voltage insulation systems, the most commonly used material is polymeric material because of its high dielectric strength, high resistivity, and low dielectric loss in addition to good chemical and mechanical properties. In this work, various polymer compounds were prepared, consisting of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), HDPE/PP, and LDPE/PP polymer blends. The relative permittivity and breakdown strength of each sample types were evaluated. In order to determine the physical properties of the prepared samples, the samples were also characterized using differential scanning calorimetry (DSC). The results showed that the dielectric constant of PP increased with the increase of HDPE and LDPE content. The breakdown measurement data for all samples were analyzed using the cumulative probability plot of Weibull distribution. From the acquired results, it was found that the dielectric strengths of LDPE and HDPE were higher than that of PP. Consequently, the addition of LDPE and HDPE to PP increased the breakdown strength of PP, but a variation in the weight ratio (30%, 50% and 70%) did not change significantly the breakdown strength. The DSC measurements showed two exothermic crystallization peaks representing two crystalline phases. In addition, the DSC results showed that the blended samples were physically bonded, and no co-crystallization occurred in the produced blends.
Space charge phenomena on low-density poly ethylene film breakdown under heavy water absorption
TELKOMNIKA Telecommunication Computing Electronics and Control, 2020
The effect of dry and heavy water absorption on the electrical breakdown of low-density poly ethylene film was investigated. The temperature rise of the sample was observed by thermograph until the electrical breakdown using direct current ramp voltage. The conduction current of low-density poly ethylene film was also measured, and the result was then correlated with thermograph measurement. Meanwhile, the space charge distribution in asample was measured by the pulse electro-acoustic method. From the thermograph, the result can be seen that under the heavy water absorption, the sample was more dissipated than the dry condition. Then, the breakdown occurs at the lower value of the voltage application, but the higher conduction current. Furthermore, the pulse electric acoustic show that increases the charge injection to the sample in the heavy water absorption. Increased space charges associated with an increase in the current conduction and the formation of heating, which results in a thermal breakdown.
Analysis of electric conduction mechanisms in polyethylene terephthalate
Materials Letters, 1998
The isothermal current-voltage measurements on insulating materials can be improved by using a symmetric triangular signal. The measured current is field dependent and the Richardson-Schottky, the Fowler-Nordheim, the Poole-Frenkel, Ohm, space charge limited current and ionic current mechanisms can be used for the interpretation of the results. The experimental data can fit with two or more from the presented mechanisms. In deciding which is the best mechanism, it is necessary to use a second condition. We propose to use the slope of the Richardson-Schottky and the Poole-Frenkel plots to calculate the dielectric permittivity of the sample. For high fields the work function can be determined from the Fowler-Nordheim plot and can be used as a control parameter. Polyethylene terephthalate was used as standard material to Ž y1 y1 . test the validity of these models under moderate electric fields 0.5 MV m -E -20 MV m . For low fields Ohm's law describes the current flow. The Richardson-Schottky law is adequate only for a small field range. The Poole-Frenkel law fits best the experimental data. For high fields the Fowler-Nordheim law fits as well the experimental results. The charge accumulated in the sample strongly influences the measured current. q 1998 Elsevier Science B.V.
Influence of Electric Field and Low Pressure on the Activation Energy for Conduction in Polyethylene
physica status solidi (a), 1982
On the basis of existing data it is suggested that the apparent activation energy for conduction in polyethylene measured between m 0 and 80 "C decreases with increasing field and pressure. This effect cannot be completely described by existing theories but data obtained under very different experimental conditions f i t an approximate phenomenological relation between activation energy, field, and low pressure. The scatter of mobility values of several polymers can be explained in part by the field effect. I n light of such findings, some suggestions are made regarding the best experimental conditions in electrical conductivity measurements in polymers. A partir des donnees existantes il est sugg6re que 1'6nergie d'activation de la conduction dans le polykthylkne entre 0 et 80 "C decroit avec des champs et pressions croissants. L'effet observe n'obeit pas aux theories existantes mais peut btre decrit par une relation approximative entre 1'6nergie d'activation, le champ et les basses pressions. La dispersion des valeurs de mobilite de plusieurs polymhres peut &re expliquee par l'effet du champ. Des suggestions sont faites concernant les meilleures conditions experimentales pour la mesure de la conductivite Blectrique des polymhres.
Hot electron and partial-discharge induced ageing of polymers
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Insulating polymers used in electrical engineering applications age under the combined effects of electrical, thermal, mechanical and environmental stresses. Of particular relevance is the electric stress that can initiate material degradation reactions through energetic processes such as partial discharges and hot electrons. Although the degradation can take specific form (microcavities, electrical treeing) depending on the time scale considered, similarities might exist in the aging mechanisms of polymers working in high voltage environment, and those exposed to plasma or radiation. Of particular interest is to identify the polymer excited states that are involved in the early stage of electrical ageing. Information on their nature can be obtained by analyzing the solid state luminescence stimulated by an electric field, UV source or fast electron beam.
Electrical conduction in parylene HT: transient and steady-state analyses at high temperature
IEEE Transactions on Dielectrics and Electrical Insulation, 2015
The electrical conduction of Parylene HT films, a high performance fluorinated parylene, is investigated at high temperature (200 to 350 °C), high electric field (5 and 360 MV/m) and for different thicknesses (1.2 to 5 µm). The steady-state currents are analyzed by assuming different conduction models. Whereas the Schottky and Poole-Frenkel models are the less probable, the thermally assisted hopping mechanism appears as the most probable conduction mechanism for fields up to the threshold (~150 MV/m). Based on the analysis of the hopping jump distance and its evolution versus temperature, an ionic hopping conduction has been proposed as the most probable charge carriers' origin to describe our results. Finally, the film thickness and the field polarity are studied. Results indicate that positive carriers (holes) are the main contributors to the injection current for high electrical fields.
Effect of partial discharges on impregnated polypropylene films
IEEE Transactions on Dielectrics and Electrical Insulation, 1994
The effect of partial discharges in benzyltoluene upon impregnated polypropylene films has been studied in a sphere/plane electrode geometry. It is shown that discharges even with a small apparent charge (-1 pC) cause a significant decrease of the breakdown strength of the film. The addition of an epoxy compound to the liquid notably reduces the film degradation characterized by the breakdown voltage, in spite of the increase of the repetition rate and apparent charge of the discharges.
Proceedings of IEEE Conference on Electrical Insulation and Dielectric Phenomena - (CEIDP'94), 1994
We have presented the effects of voltage-thermal and voltage-chemical aging of LLDPE on the conduction behavior, dielectric loss and AC breakdown strength. Any molecular structure changes are not observed in all the stressed LLDPE samples from FTIR analysis. From DSC measurement, we have observed that electrical stress assisted by thermal effect may cause the morphological changes, such as reorganization and degradation of crystalline, amorphous phase and their boundaries in the voltage-thermal stressed LLDPE. These morphological changes may be responsible for the increase of the detrapping or releasing of carriers and hopping through the amorphous phase in the voltage-thermal stressed LLDPE. Schottky process together with hopping may become dominant in the conduction behavior of long-term voltage-thermal stressed LLDPE(VTl1 OOH). There are little superficial changes of morphology in voltage-chemical stressed LLDPE. A conduction mechanism of the voltage-chemical stressed LLDPE has not been changed significantly compared with that of virgin LLDPE. The different trends of increase or decrease of the dielectric loss and AC breakdown strength for the volatge-thermal and voltage-chemical stressed LLDPE may be due to the morphological changes.
Electrical conduction processes in polyimide-teflon® FEP films-II
IEEE Transactions on Dielectrics and Electrical Insulation, 2008
Extensive investigations of the absorption and desorption currents are carried out over the temperature range of 50 to 200 o C and electric fields up to 12 MV/m in 25.5 μm polyimide film base with 12.7 μm coating of Teflon ® FEP on one side. It is believed that this is the first time that studies on this film are reported in the literature.