• Title/Summary/Keyword: surface aging

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The Aging Characteristics of Polymer Electrical Insulation Materials bv UV Radiation and Salt Water Spray (옥외용 고분자 전기절연재료의 염수 및 UV조사에 의한 열화 특성)

  • 최남호;한상일;한상옥;박강식;김종석;박양범
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1997.11a
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    • pp.221-224
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    • 1997
  • In this study we investigated the acting characteristics of Polymers for electrical insulation by UV radiation and salt water spray treatment. We used the Polymers such as EPDM, SR. PTFE. EVA. We measured contact angle and surface resistance to know the aging characteristic of Polymer surface. And we use SEM to observe the change of the surface shape. Dry flashover voltage test impulse voltage test were carried for the polymer insulator(EVA) . Through this experiment and the analysis we could know the polymers have a good resistance to weathering conditions like as salt spray UV irradiation and mix of them. And we can compare the aging characteristics between Polymers. As a result, we could know that the surface characteristics of PTFE is better than the other. And the degree, electrical characteristics is affected by change of surface shape is not big.

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Evaluation of the bond strength between aged composite cores and luting agent

  • Polat, Serdar;Cebe, Fatma;Tuncdemir, Aliriza;Ozturk, Caner;Usumez, Aslihan
    • The Journal of Advanced Prosthodontics
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    • v.7 no.2
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    • pp.108-114
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    • 2015
  • PURPOSE. The aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent. MATERIALS AND METHODS. Seventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to $55^{\circ}C$) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at ${\alpha}$=.05. RESULTS. Thermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between $7.07{\pm}2.11$ and $26.05{\pm}6.53$ N. The highest bond strength of $26.05{\pm}6.53$ N was obtained with Group 3. Group 5 showed the lowest value of bond strength. CONCLUSION. Appropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success.

Leakage Current Waveforms and Spectrum Analysis of EPDM Polymer Insulator according to Environment Condition (환경조건에 따른 EPDM 고분자 애자의 누설전류파형과 스펙트럼 분석)

  • Park, Jae-Jun;Kim, Jeong-Boo;Song, Young-Chul
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.05b
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    • pp.82-86
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    • 2004
  • This research is about the result of leakage current waveform about the situation of surface leakage current and environmental changes(Salt fog, clean fog and rain) by EPDM polymer insulators' amount of salt. The researcher presents the result of changing about fundamental harmonic, 3rd harmonic and 5th harmonic from starting point of supplying power to flashover. In this study, researched environmental affects (clean fog, salt fog and rain) about surface aging of polymer insulators and used frequency spectrum of leakage current waveform to develop the diagnostic technique of surface aging. When amount of salt contents changed, surface aging stage and the degree of aging (distortion factor) about 3rd and 5th harmonic waveform on low frequency harmonic wave. The distortion factor which is harmonic percentage about basic harmonic is important pointer to evaluate the surface condition of polymer insulators.

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Partialt Discharge Measurement Techniques for Diagnosis of Surface Aging on Organic Insulation (고체 합성수지절연체와 표면노화 진단기술로서의 부분방전 측정평가기술에 대하여)

  • 박완기
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1994.05a
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    • pp.50-56
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    • 1994
  • Partial discharge on organic insulation surfaces are an important sauce of aging. Furthermore the modern PD measurement technigues are rapid developed as quality control and diagnostic tests to determine the fitness for use of HV equipment employing sol id electrical insulation. This paper deals with theory of conventional PD measurement and new tendency of technical development on PD measurements und evaluations. Finally the Measuring system used for diagnosing the surface aging on the organic insulation at High Voltage Laboratory of Technical University of Darmstadt in Germany is presented.

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Synthesis and Characterization of Nanoporous Boehmite (나노세공 보에마이트의 합성 및 그 특성평가)

  • Kim Ho-Kun;Kim Tae-Young
    • Journal of Powder Materials
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    • v.12 no.3
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    • pp.220-224
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    • 2005
  • Boehmite (AlOOH) powder with uniform pore size and high specific surface area were synthesized via sol-gel method using metal salts, $Al_2(SO_4)_3$ and $NaAlO_2$. During these synthetic process, the effects of the aging time were investigated to determine the optimal synthetic conditions of boehmite. X-ray diffraction, BET, Raman/IR, and scanning electron microscopy techniques were used for the characterization of the powder. Boehmite gel synthesized at the first stage of the experimental procedure transformed to crystalline boehmite phase after aging for 6 hours. The specific surface area of the crystalline boehmite showed a maximum value, $350m^2/g$, at aging time of 72 hours. The pore size of the boehmite increased with increasing aging time and the boehmite with average pore diameter of 3.6 nm was obtained at aging time of 96 hours.

An Evaluation of Fatigue Life for Aging Aircraft Structure (장기운용항공기 구조물의 잔여 피로수명예측 기법)

  • Lee, Eungyeong;Jeong, Yooin;Kim, Sangshik
    • Korean Journal of Materials Research
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    • v.25 no.10
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    • pp.516-522
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    • 2015
  • Aging aircraft structures are inevitably exposed to environment for a long time facing many potential problems, including corrosion and wide spread fatigue damage, which in turn cause the degradation of flight safety. In this study, the environmental surface damages on aging aircraft structures induced during service were quantitatively analyzed. Additionally, S-N fatigue tests were performed with center hole specimens extracted from aging aircraft structures. From the results of quantitative analyses of the surface damages and fatigue tests, it is concluded that corrosion pits initiated during service reduce the fatigue life significantly. Finally, using the fracture mechanics and the EIFS (equivalent initial flaw size) concepts, the remaining fatigue life was predicted based on actual fatigue test results.

Comparative evaluation of shear bond strength of orthodontic brackets bonded to three-dimensionally-printed and milled materials after surface treatment and artificial aging

  • Ameer Biadsee;Ofir Rosner;Carol Khalil;Vanina Atanasova;Joel Blushtein;Shifra Levartovsky
    • The korean journal of orthodontics
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    • v.53 no.1
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    • pp.45-53
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    • 2023
  • Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials. Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 ㎛ aluminum oxide particles (SA) and aging; group B, sandblasted with 30 ㎛ silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed (p = 0.05). Results: The retention obtained with the 3D-printed materials (groups A-D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) (p = 0.037). Study groups A-D predominantly exhibited a cohesive specimen mode, indicating specimen fracture. Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

Aging Characteristics of Cable Terminations for Distribution Power System (배전용 케이블 종단접속재의 경년특성)

  • Han, Jae-Hong;Lee, Byeong-Seong;Kim, Sang-Jun;Lee, Cheol-Ho;Kim, Sang-Uk;Kim, Yong-Ae
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.8
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    • pp.580-586
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    • 1999
  • Aging characteristics of 13 years service-aged distribution cable terminations which dismounted from 3 regions were investigated by material characterization and electrical test. All dismounted terminations have propagating micro-cracks on the surface of weathershed and chalking fillers from bulk. Elemental analysis of these terminations showed that the carbon was decreased and the oxygen was increased on the surface of weathershed due to a little oxidation reaction. Contact angle of terminations was abnormally increased with time. In the analysis of anti-oxidation ability and chemical structure, there were no differences between new and dismounted terminations. All terminations showed satisfactory results in electrical test. Therefore, itcan be considered that aging is only propagating on the surface of dismounted terminations. Also, it was confirmed that environmental factors such as UV, pollution and salt have an effect on the aging through the observation of polymer composition change.

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Selective Dissolution of ZnO Crystal by a Two-step Thermal Aging in Aqueous Solution (수용액 합성법의 2단계 성장온도 변화를 통한 ZnO 결정의 선택적 용해 현상)

  • Kim, Jeong-Seog;Chae, Ki-Woong
    • Journal of the Korean Ceramic Society
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    • v.48 no.4
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    • pp.263-268
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    • 2011
  • ZnO hexagonal rods grown in aqueous solution can be changed into a tubular shape by two-step aging in the course of the growing process. In the first step, hexagonal ZnO rods is grown by aging at $90^{\circ}C$ under a highly supersaturated aqueous solution giving rise to a fast precipitation rate. Meanwhile, during the second step aging at $60^{\circ}C$ in the same aqueous solution, the hexagonal polar face (001) having higher surface energy than (010) side planes dissolves to minimize surface energy. Hence the flat (001) face changes to a craterlike face and the hexagonal rod length of ZnO decreases at an initial-stage of this step aging. The formation of the (101) wedge-type faces is ascribed to the resultant of competitive reactions between the dissolution of polar face minimizing the surface energy which is a dominant reaction at the initial stage and the precipitation reaction dissipating supersaturation. At a later stage of the second-step the reaction rates of these two processes in the aqueous solution become similar and the overall reaction is terminated.