• Title, Summary, Keyword: RTV

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A Study on Ageing Characteristics of RTV Silicone Coating Materials by Corona Discharge (RTV 실리콘 코팅재의 코로나 방전 열화 특성)

  • 한세원;한동희;조한구
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.52 no.8
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    • pp.359-364
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    • 2003
  • Ageing characteristics of RTV coating materials by corona discharge have been studied. The hydrophobicity recovery of RTV coating materials with 300${\mu}{\textrm}{m}$ thickness was identical with a bulk silicone materials. The RTV coating materials hydrophobicity has been almost lost when its were discharged during 40 seconds by corona discharge of 10㎸, and recovered after about 45 hours. The resistivity of RTV coating materials has not been recovered after 45 hours, though after 80 hours the initiation resistivity value has been recovered up to 95%. There was no critical change of compounds(such as Si and Al) on RTV surfaces by the corona discharge treatment until 100 seconds. In the test of arc erosion, it was seen that the coating sample with silicone rubber as a base material have more longer burn-out time than other samples with FRP or glass base.

The Effects of Environmental Factors on Degradation and Hydrophobicity Recovery Characteristics in RTV Silicone Rubber (RTV 실리콘 고무의 열화 및 발수성 회복 특성에 미치는 환경인자의 영향)

  • Heo, Chang-Su;Yeon, Bok-Hui;Jo, Hyeon-Uk;Hwang, Myeong-Geun
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.6
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    • pp.462-468
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    • 1999
  • Room temperature vulcanizing (RTV) silicone rubber has been widely used to coat porcelain insulators to render water repellency to prevent formation of water film on the surface and thus to suppress the leakage current and consequently flashover. However, the electrical property and the hydrophobicity of RTV silicone rubber coating under outdoor condition may be influenced by many environmental factors. In this studyvarious treatments, such as salt-fog, salt water immerging and UV irradiation were applied to the samples to investigate the change of the electrical property and hydrophobicity. As a result the leakage current increased and contact angle decreased asthe degradation time is longer. But the degraded RTV silicone rubber has recovered its hydrophobicity during the drying time in ambient condition because LMW(Low Molecular Weight) silicone fluid diffused from the bulk to the surface.

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Study on electrical ageing properties of ATV silicone coatings (RTV 실리콘 코팅재의 전기적 열화 특성 연구)

  • Han, Se-Won;Cho, Han-Goo;Han, Dong-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.35-39
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    • 2003
  • An ageing characteristics of RTV coating materials by corona discharge have been studied. The recovery of a hydrophobicity of RTV coating materials with the thickness of $300{\mu}m$ was in identical with a bulk silicone materials. The hydrophobicity of RTV coating materials has been almost lost when its were discharged during 40 seconds by corona with 10kV, and recovered after about 45 hours. But the resistivity of RTV coating materials has not been recovered after 45 hours, even though after 80 hours the 95% of initiation resistivity value has been recovered. There was no critical compounds(such as Si and Al) changes on RTV surfaces by the corona discharge treatment until 100 seconds. In the test of arc erosion, it was seen that the coating sample with silicone rubber as a base material have more longer bum-out time than other samples with FRP or glass base.

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Effect of Accumulated charges on Surface Hydrophobicity of RTV Silicone Rubber (RTV 실리콘 고무 코팅재의 표면전하 축적이 발수성에 미치는 영향)

  • 연복희;허창수;조한구
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.597-600
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    • 2001
  • In this paper, we evaluated the effect of accumulated charges on hydrophobicity of room temperature vulcanized(RTV) silicone rubber, which could improve the contamination performance of porcelain insulators, with uv radiation time. Outdoor insulating material could be charged by the corona discharge on field intensified area of insulator and discharge between the water drops. In addition, we performed the accelerated uv radiation on samples and investigated the change of charging decay with time. In this results, it is found that silica-like structure on the surface of RTV silicone rubber was formed by uv treatments and this layer have the characteristic of retaining the charges on surface for a long time. These charges have effects on its hydrophobicity and so adversely effects on contamination performance. Based on our results, we discussed the other degradation mechanism with well known ones.

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A Study on Anti-Pollutions Characteristics of RTV Silicone Rubber (RTV 실리콘 고무의 내오손 특성에 관한 연구)

  • Huh, Chang-Su;Lee, Sang-Youb;Youn, Bok-Hee;Hwang, Myung-Kun;Lee, Jong-Han
    • Proceedings of the KIEE Conference
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    • pp.1651-1653
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    • 1999
  • Room Temperature Vulcanizing (RTV) Silicone Rubber has been widely used to coat porcelain insulator to prevent formation water filming on insulator surface. and RTV silicone rubber has water repellency to suppress leakage current and consequent flashover. RTV silicone rubber's surface has been degradated by outdoor condition such as dust, salt, and water. etc. ESDD(Equivalent Salt Deposit Density) and leakage currents are increased by polymer surface toughness and degradation. In this paper, we investigated relations of surface toughness, ESDD, and leakage currents.

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Degradation Characteristics of RTV Silicone Rubber by environmental Factors (환경 인자에 의한 RTV 실리콘 고무의 열화 특성)

  • Cho, Hyun-Wook;Huh, Chang-Suh
    • Proceedings of the KIEE Conference
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    • pp.866-868
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    • 1998
  • Room temperature vulcanizing(RTV)silicone rubber has been widely used to coat porcelain insulators to render water repellency to prevent formation of water filming on the surface and thus to suppress the leakage current and consequent flashover. However, the electrical property and its hydrophobicity of RTV silicone rubber coating under outdoor conditions may be influenced by many environmental factors. In this study various treatments, such as salt-fog, salt water immerging and UV irradiation were applied to samples for investigation the change of the electrical property and hydrophobicity. As a result the leakage current increased and contact angle decreased as the degradation time longer. But the degraded RTV silicone rubber has recovered its hydrophobicity during the drying time in ambient condition because LMW(Low Molecular Weight)silicone fluid diffused from the bulk to the surface.

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Effect of cyclic loading and retightening on reverse torque value in external and internal implants

  • Cho, Woong-Rae;Huh, Yoon-Hyuk;Park, Chan-Jin;Cho, Lee-Ra
    • The Journal of Advanced Prosthodontics
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    • v.7 no.4
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    • pp.288-293
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    • 2015
  • PURPOSE. The aim of this study was to evaluate the effect of cyclic loading and screw retightening on reverse torque value (RTV) in external and internal type implants. MATERIALS AND METHODS. Cement-retained abutments were connected with 30 Ncm torque to external and internal type implants. Experimental groups were classified according to implant connection type and retightening/loading protocol. In groups with no retightening, RTV was evaluated after cyclic loading for 100,000 cycles. In groups with retightening, RTV was measured after 3, 10, 100 cycles as well as every 20,000 cycles until 100,000 cycles of loading. RESULTS. Every group showed decreased RTV after cyclic loading. Before and after cyclic loading, external type implants had significantly higher RTVs than internal type implants. In external type implants, retightening did not affect the decrease in RTV. In contrast, retightening 5 times and retightening after 10 cycles of dynamic loading was effective for maintaining RTV in internal type implants. CONCLUSION. Retightening of screws is more effective in internal type implants than external type implants. Retightening of screws is recommended in the early stage of functional loading.

Relation between Surface degradation and Anti-pollution Characteristics in RTV Silicone Rubber (RTV 실리콘 고무의 표면열화와 내오손 특성과의 상관관계)

  • 연복희;이태호;허창수;이상엽
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.7
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    • pp.598-606
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    • 2000
  • In this paper we investigated the relation between the surface degradations and anti-pollution characteristics of Room Temperature Vulcanized(RTV) silicone rubber coating that has different roughness through immersing into saline water. We utilized several analytic techniques such as atomic force microscopy(AFM) scaning electron microscopy(SEM) contact angle Salt Deposit Density(SDD) and average leakage current under the condition of salt fog. It is found that the surface roughness of treated RTV silicone rubber increased and the hydrophobicity of sample surface decreased with increasing the duration o immersion into water due to the erosion of base polymer the melting down alumina trihydrate(ATH) and the diffusion of Low Molecular weight(LMW) fluid. Despite the roughness of surface had been increased by water immersion excellant anti-pollution and recovery characteristics were maintained and SDD saturated to 0.1~0.14mg/cm$^2$. The average leakage current under salt fog increased with surface roughness. Measurement of average leakage current will be helpful to investigate surface degradation and lifetime expectation of RTV silicone coating.

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Effect of cement washout on loosening of abutment screws and vice versa in screw- and cement- retained implant-supported dental prosthesis

  • Kim, Seok-Gyu;Chung, Chae-Heon;Son, Mee-Kyoung
    • The Journal of Advanced Prosthodontics
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    • v.7 no.3
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    • pp.207-213
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    • 2015
  • PURPOSE. The purpose of this study was to examine the abutment screw stability of screw- and cement-retained implant-supported dental prosthesis (SCP) after simulated cement washout as well as the stability of SCP cements after complete loosening of abutment screws. MATERIALS AND METHODS. Thirty-six titanium CAD/CAM-made implant prostheses were fabricated on two implants placed in the resin models. Each prosthesis is a two-unit SCP: one screw-retained and the other cemented. After evaluating the passive fit of each prosthesis, all implant prostheses were randomly divided into 3 groups: screwed and cemented SCP (Control), screwed and non-cemented SCP (Group 1), unscrewed and cemented SCP (Group 2). Each prosthesis in Control and Group 1 was screwed and/or cemented, and the preloading reverse torque value (RTV) was evaluated. SCP in Group 2 was screwed and cemented, and then unscrewed (RTV=0) after the cement was set. After cyclic loading was applied, the postloading RTV was measured. RTV loss and decementation ratios were calculated for statistical analysis. RESULTS. There was no significant difference in RTV loss ratio between Control and Group 1 (P=.16). No decemented prosthesis was found among Control and Group 2. CONCLUSION. Within the limits of this in vitro study, the stabilities of SCP abutment screws and cement were not significantly changed after simulated cement washout or screw loosening.

Effect of Long-term Corona-discharge on RTV Silicone Rubber (장기 코로나 처리에 따른 RTV 실리콘 절연재료의 특성변화)

  • Youn, Bok-Hee;Ahn, Jong-Sik;Huh, Chang-Su
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.266-269
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    • 2001
  • This paper investigated the aging characteristic under long-term corona discharge on roan temperature vulcanized silicone rubber, which has been using as a protective coating material for solving the contaminant problem. The applied electrical field is 10kV/cm ac and corona discharge treatment was applied on RTV silicone rubber sheet for maximum 250 hours. With the duration of corona discharge. the diffusible low molecular weight species increased, which was determined the usage of n-hexane extraction method. In addition, the contaminant layer was formed on the treated surface, and then measured the contact angle. We investigated the relation of contact angle and diffusible low molecular weight species. It is found that scissor of main chain PDMS and side chains $(CH_3)$ and the generation of LMW species were occurred by a corona discharge. The improvement of hydrophobicity rate is thought due to the increase of diffusible LMW species.

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