氏名

ヒライ ナオシ

平井 直志

職名

主任研究員(研究院准教授) (https://researchmap.jp/read0078137/)

所属

(各務記念材料技術研究所)

連絡先

メールアドレス

メールアドレス
nhirai@aoni.waseda.jp

URL等

研究者番号
30329122

本属以外の学内所属

学内研究所等

循環型環境経済共創システム研究所

研究所員 2010年-2013年

学歴・学位

学歴

-1994年 甲南大学 理学部 応用物理
-1998年 愛媛大学 工学研究科 生産工学

学位

博士(工学) 課程 愛媛大学

修士(理学) 課程 甲南大学

所属学協会

電気学会

放電学会

受賞

電気学会優秀論文発表賞

2000年

電気学会優秀論文発表賞

1993年

研究分野

科研費分類

工学 / 電気電子工学 / 電子・電気材料工学

研究テーマ履歴

高分子誘電体の電気特性の研究

研究テーマのキーワード:ポリエチレン,空間電荷分布,残留電圧

機関内共同研究

新しい絶縁方式の開発

研究テーマのキーワード:自己修復材料,インテリジェント材料,センサ機能材料

国内共同研究

誘電体中の電荷分布の実時間測定

個人研究

架橋剤分解残渣の有機高分子絶縁材料に与える影響

個人研究

誘電体の絶縁特性の研究

個人研究

生分解性高分子の電気特性

個人研究

論文

L型ポリ乳酸の絶縁破壊

2004年電気学会基礎・材料・共通部門大会講演論文集p. 4552004年08月-

L型ポリ乳酸の電気伝導特性に及ぼすガラス転移の影響

2004年電気学会基礎・材料・共通部門大会講演論文集pp. 130-1352004年08月-

絶縁体中の電荷移動とデトラッピングに関する基礎電磁気学

静電気学会誌Vol. 28, No. 4, pp. 204-2072004年07月-

Dielectric properties of biodegradable polylactic acid and starch ester

Proceedings of the 2004 IEEE International Conference on Solid Dielectricspp. 87-902004年07月-

生分解性・リサイクル材料の電力機器用絶縁材料としての評価

平成16 年電気学会全国大会講演論文集第2分冊、pp. 2-S7(11)-2-S7(14)2004年03月-

L型ポリ乳酸の電荷トラップに影響を与える因子

平成16 年電気学会全国大会講演論文集第2分冊、pp. 130-1312004年03月-

クミルアルコールが80℃の低密度ポリエチレン中の空間電荷形成に与える影響

平成16 年電気学会全国大会講演論文集第2分冊、p. 752004年03月-

生分解性高分子L型ポリ乳酸の伝導電流に及ぼすガラス転移の影響

平成16 年電気学会全国大会講演論文集第2分冊、pp. 132-1332004年03月-

生分解性エステル化澱粉におよぼす紫外光照射の影響

平成16 年電気学会全国大会講演論文集第2分冊、p. 1292004年03月-

我国における電力機器絶縁監視・診断法の変遷と現状

電気学会部門誌B124-B, No. 3, pp. 496-5032004年03月-

Comparison of Surface Roughness Change due to Partial Discharges between Polyamide-6 and Nanocomposites

Proceedings of the 2003 Japan-Korea Joint Symposium on Electrical Discharge and High Voltage Engineeringpp. 33-362003年11月-

Roles of cumyl alcohol and crosslinked structure in homo-charge trapping in crosslinked polyethylene

Annual Report of the 2003 Conference on Electrical Insulation and Dielectric Phenomenapp. 213-2162003年10月-

Surface change of polyamide nanocomposite caused by partial discharges

Annual Report of the 2003 Conference on Electrical Insulation and Dielectric Phenomenapp. 75-782003年10月-

生分解性高分子ポリ乳酸および修飾澱粉の誘電特性

2003年電気学会基礎・材料・共通部門大会講演論文集p. 2782003年08月-

架橋ポリエチレン中の空間電荷形成に与える架橋剤分解残渣の効果

2003年電気学会基礎・材料・共通部門大会講演論文集pp. 160-1652003年08月-

Effect of Crosslinking on Space Charge Formation in Crosslinked Polyethylene

Proceedings of the 7th International Conference on Properties and Applications of Dielectric Materialspp. 917-9202003年06月-

Chemical Group in Crosslinking Byproducts Responsible for Charge Trapping in Polyethylene

IEEE Trans. Dielectrics and Electrical InsulationVol. 10, No. 2, pp. 320-3302003年04月-

電力機器の絶縁劣化診断法の変遷と現状

2003年電気学会全国大会講演論文集第2分冊 pp. 99-1002003年03月-

架橋ポリエチレン中のホモ電荷トラップに及ぼすクミルアルコールの役割

2003年電気学会全国大会講演論文集第2分冊 p. 722003年03月-

架橋ポリエチレンの空間電荷形成に与える架橋構造の影響

平成15年放電、誘電・絶縁材料合同研究会資料pp. 51-562003年01月-

脱気処理が架橋ポリエチレンの空間電荷分布形成に及ぼす影響

第34回電気電子絶縁材料システムシンポジウム予稿集pp. 197-2002002年11月-

Chemical Group in Crosslinking Byproducts Responsible for Charge Trapping in Polyethylene

Annual Report of the 2002 Conference on Electrical Insulation and Dielectric Phenomenapp. 626-6302002年10月-

Interpretation of the Relation between Residual Charge and Water Trees in XLPE Cables

Proceedings of IEEE/PES Transmission and Distribution Conference and Exhibition 2002pp. 1094-10992002年10月-

架橋構造がポリエチレン中の空間電荷形成に与える影響

2002年電気学会基礎・材料・共通部門大会講演論文集p. 2952002年09月-

低密度ポリエチレン中の空間電荷形成に与る架橋剤分解残渣の化学基

平成14年誘電・絶縁材料、電線・ケーブル合同研究会資料pp. 7-122002年06月-

水トリー劣化架橋ポリエチレンの残留電荷の測定と解釈

電気学会部門誌A122巻6号 pp. 597-6032002年06月-

ポリエチレンにおける紫外光誘起フォトルミネセンス(その1)-LDPEとXLPEの比較-

平成14年電気学会全国大会講演論文集2pp. 93-942002年03月-

ポリエチレンにおける紫外光誘起フォトルミネセンス(その2)-発光帯の原因-

平成14年電気学会全国大会講演論文集2p. 912002年03月-

ポリエチレンの電気絶縁特性に及ぼすブレンド効果

平成14年電気学会全国大会講演論文集2pp. 85-862002年03月-

クミルアルコールが架橋ポリエチレンの空間電荷形成に与える影響

平成14年電気学会全国大会講演論文集2pp. 68-692002年03月-

ポリエチレン架橋剤分解残渣の電荷トラップ作用に与る化学構造

平成14年電気学会全国大会講演論文集2pp. 56-572002年03月-

パルス静電応力法による紫外光照射ポリイミドの劣化評価

平成14年電気学会全国大会講演論文集2pp. 54-552002年03月-

ポリエチレン中の空間電荷分布形成に与える架橋剤分解残渣の影響

電気学会部門誌A122巻3号、pp. 308-3142002年03月-

ポリイミドの耐水・耐アルカリ性—残留電圧等電気的測定による評価—

電気学会論文誌A121巻12号、pp. 1117-11242001年12月-

Effect of blending on the dielectric breakdown of polyethylene

Proceedings of the 2001 International Symposium on Electrical Insulating Materialspp. 574-5772001年11月-

Effects of Liquid Chemicals on Space Charge Evolution in Low-density Polyethylene

Proceedings of the 2001 International Symposium on Electrical Insulating Materialspp. 87-902001年11月-

On the Mechanism of Recovery Voltage in a Dielectric Solid - Proposal of a Simple Equation-

Proceedings of the 2001 International Symposium on Electrical Insulating Materialspp. 67-702001年11月-

Evaluation of Degradation in Polyimide by Recovery Voltage Measurement

Annual Report of the 2001 Conference on Electrical Insulation and Dielectric Phenomenapp. 216-2202001年10月-

Effect of Byproducts of Dicumyl Peroxide on Space Charge Formation in Low-density Polyethylene

Annual Report of the 2001 Conference on Electrical Insulation and Dielectric Phenomenapp. 478-4832001年10月-

非架橋ケーブル用高分子絶縁材料の電気特性

2001年電気学会基礎・材料・共通部門大会講演論文集p. 3392001年09月-

絶縁体における残留電圧発生機構の検討 −簡単化した計算式の提案−

2001年電気学会基礎・材料・共通部門大会講演論文集p. 3352001年09月-

架橋剤分解残渣がLDPEの空間電荷挙動に与える影響 −類似の化学薬品との比較−

2001年電気学会基礎・材料・共通部門大会講演論文集p. 3252001年09月-

ポリエチレンにおける紫外光誘起フォトルミネセンス

2001年電気学会基礎・材料・共通部門大会講演論文集p. 3132001年09月-

ポリプロピレンの紫外光誘起フォトルミネセンス

電気学会論文誌A121巻9号, pp. 865-8712001年09月-

直鎖状低密度ポリエチレンの絶縁特性に影響を与える因子

電気学会論文誌A121巻9号, pp. 854-8592001年09月-

Effects of Byproducts of Dicumyl Peroxide on Space Charge Formation in Polyethylene

The Proceedings of 7th International Conference on Solid Dielectricspp. 450-4552001年06月-

Photoluminescence in Polymeric Insulating Materials (Low Density Polyethylene and Polypropylene) induced by ultraviolet photons

The Proceedings of 7th International Conference on Solid Dielectricspp. 319-3232001年06月-

水トリー劣化架橋ポリエチレンの残留電荷

平成13年誘電・絶縁材料研究会資料DEI-01-92、pp. 25-302001年06月-

クミルアルコールが低密度ポリエチレンの電荷挙動に与える影響

平成13年電気学会全国大会予稿集p. 5802001年03月-

残留電圧測定によるポリイミドの劣化の評価

平成13年電気学会全国大会予稿集p. 5652001年03月-

全芳香族ポリイミドと熱可塑性ポリイミドの劣化の評価

電気学会 放電/誘電・絶縁材料合同研究会資料DEI-01-78、pp. 105-1102001年03月-

高分子絶縁体(LDPE,PP)の紫外光誘起フォトルミネセンス

電気学会 放電/誘電・絶縁材料合同研究会資料DEI-01-77、pp. 99-1042001年03月-

架橋剤分解残渣がポリエチレンの空間電荷分布形成に与える影響

電気学会 放電/誘電・絶縁材料合同研究会資料DEI-01-76、pp. 93-982001年03月-

ポリエチレン中の空間電荷形成にクミルアルコールの与える影響

第32回電気電子絶縁材料システムシンポジウム予稿集pp. 25-282000年11月-

Effects of Byproducts of Crosslinking Agent on Space Charge Formation in Polyethylene.-comparison between acetophenone and α-methylstyrene-

Annual Report of the 2000 Conference on Electrical Insulation and Dielectric Phenomenapp. 535-5382000年10月-

低密度ポリエチレンの紫外レーザー光誘起フォトルミネセンス

2000年電気学会基礎・材料・共通部門大会予稿集p. 402000年09月-

クミルアルコールがポリエチレンの空間電荷形成に与える影響

2000年電気学会基礎・材料・共通部門大会予稿集p. 372000年09月-

Comparison of degradation between all-aromatic and thermoplastic polyimide films

2000年電気学会基礎・材料・共通部門大会予稿集p. 362000年09月-

架橋剤分解残渣がポリエチレンの空間電荷形成に与える影響 −アセトフェノンとαメチルスチレンの比較—

平成12年誘電・絶縁材料研究会資料DEI-00-55、pp. 19-262000年06月-

The Effect of Contaminant in Breakdown Time Lag of Uniform Electric Field Using Impulse Breakdown in Mineral Oil.

1999 IEEE 13th International Conference on Conduction and Breakdown in Dielectric Liquidspp. 207-2101999年07月-

The Effect of Electrode Construction in Breakdown Time Lag of Impulse Breakdown in Mineral Oil.

Japanese Journal of Applied Physics(JJAP)Vol.37 pp.4884-48861998年09月-

The Effect of Copper Powder and Aluminium Oxide on Breakdown Time Lag of Transformer Oil Under Uniform Field.

the Fourth International Conference KSEEE’981998年08月-

Location feasibility of degradation in cable through Fourier transform analysis of broadband impedance spectra

Ohki, Yoshimichi;Hirai, Naoshi

ELECTRICAL ENGINEERING IN JAPAN183(1)p.1 - 82013年-2013年

DOIWoS

詳細

ISSN:0424-7760

Precise Location of the Excessive Temperature Points in Polymer Insulated Cables

Ohki, Yoshimichi;Yamada, Takayuki;Hirai, Naoshi

IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION20(6)p.2099 - 21062013年-2013年

WoS

詳細

ISSN:1070-9878

Diagnosis of surface degradation of flame-retardant ethylene propylene diene copolymer by scanning probe microscopy

Niki, Takayuki;Hirai, Naoshi;Ohki, Yoshimichi

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY53(1)p.82 - 882016年-2016年

DOIWoS

詳細

ISSN:0022-3131

原子力発電所における絶縁劣化診断の重要性およびケミルミネセンスによる酸化状態の把握

大木 義路;平井 直志

マテリアルライフ学会誌23(1)p.1 - 92011年02月-2011年02月 

CiNii

詳細

ISSN:13460633

広帯域インピーダンススペクトルのフーリエ解析によるケーブル劣化位置標定の可能性

大木 義路;平井 直志

電気学会論文誌. A, 基礎・材料・共通部門誌 = The transactions of the Institute of Electrical Engineers of Japan. A, A publication of Fundamentals and Materials Society132(2)p.122 - 1282012年02月-2012年02月 

CiNii

詳細

ISSN:03854205

概要:Since electric cables play important roles such as power supply and information transmission, their degradation may cause a serious problem. We have been trying to monitor the degradation of cable insulation by measuring the magnitude and phase angle of impedance as a function of frequency in a very wide frequency range. The cables tested were insulated with flame-retardant ethylene propylene rubber or special heat-resistant polyvinyl chloride. They were damaged partially by peeling off their insulation layers, or aged partially by heat and γ-rays. Impedance and phase angle were measured from a terminal of the cable. The difference in impedance between the damaged and sound cables becomes clear by fast Fourier transform analyses, from which the damaged portion can be located. It can be clearly shown that this method has a potential ability to detect the degradation of cable insulation induced by physical damage, γ-ray irradiation, and thermal aging.

ケーブル劣化位置標定法としての広帯域インピーダンス分光法の感度

山田 貴之;平井 直志;大木 義路

電気学会研究会資料. DEI, 誘電・絶縁材料研究会2012(53)p.11 - 162012年02月-2012年02月 

CiNii

周波数領域反射法によるケーブルの異常温度箇所の位置標定

山田 貴之;平井 直志;大木 義路;熊谷 進

電気学会研究会資料. DEI, 誘電・絶縁材料研究会2013(29)p.39 - 442013年02月-2013年02月 

CiNii

2012 IEEE International Conference on Condition Monitoring and Diagnosis (CMD2012) 会議報告

平井 直志

電気学会研究会資料. DEI, 誘電・絶縁材料研究会2013(38)p.5 - 82013年03月-2013年03月 

CiNii

研究グループ紹介:早稲田大学 理工学術院 大木義路研究室

平井 直志

電気学会論文誌. B132(5)p.NL5_2 - NL5_22012年-2012年

CiNii

詳細

ISSN:0385-4213

多くの有機高分子に現れる蛍光の電子遷移過程

西川 聖也;殿井 將史;吉川 武司;平井 直志;中井 浩巳;大木 義路

電気学会論文誌. A136(4)p.205 - 2112016年-2016年

CiNii

詳細

ISSN:0385-4205

概要:Low density polyethylene (LDPE) and polypropylene (PP) exhibit a photoluminescence (PL) band, which emits photons with an energy of around 4.3 eV when excited by photons with energies around 6.4 eV. The origin of this PL band has been assigned to α, β-unsaturated carbonyl. In this paper, the appearance of PL was examined for four kinds of polyolefin and four kinds of biodegradable polymers. As a result, it has become clear that all the polymers show a PL band with a PL excitation spectrum and a PL spectrum similar to those of the above-mentioned PL band in LDPE and PP. The decay profiles observed for these PL bands indicate that they are fluorescence. Furthermore, the intensity of the PL becomes weak for all the four polyolefin samples and the polylatic acid sample if ultraviolet photons were irradiated to the sample. Quantum chemical calculations carried out by assuming a model of α, β-unsaturated carbonyl have revealed that the PL originates in the π* to π transition of electrons in the carbon-carbon double bond.

Influence of cable structure on the fault location by frequency domain reflectometry

Ohki, Yoshimichi; Hirai, Naoshi

Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP2015-Decemberp.274 - 2772015年12月-2015年12月 

DOIScopus

詳細

ISSN:00849162

概要:© 2015 IEEE.The authors have demonstrated that the estimation of the precise locations of points in cables aged thermally or mechanically or by the irradiation of gamma rays is possible by a combination of frequency domain reflectometry (FDR) and inverse fast Fourier transform (IFFT). This paper examines how this ability of fault location depends on the type and structure of the cable, using several kinds of polymer insulated cables such as triple core cables insulated with flame-retardant ethylene propylene diene copolymer (FR-EPDM), dual core cables insulated with silicone rubber (SiR) or crosslinked polyolefin (XLPO), and coaxial cylindrical cables insulated with low density polyethylene (LDPE). As a result, for cables with lengths of 16 to 72 m, the maximum sensitivity is attained when the highest frequency of the inputted electromagnetic waves is 1.0 GHz or higher for coaxial cables, but around 600 to 800 MHz for dual or triple core cables.

Electronic transition process of fluorescence appearing in various organic polymers

Nishikawa, Seiya; Tonoi, Masashi; Yoshikawa, Takeshi; Hirai, Naoshi; Nakai, Hiromi; Ohki, Yoshimichi; Ohki, Yoshimichi

IEEJ Transactions on Fundamentals and Materials136(4)p.205 - 2112016年01月-2016年01月 

DOIScopus

詳細

ISSN:03854205

概要:© 2016 The Institute of Electrical Engineers of Japan.Low density polyethylene (LDPE) and polypropylene (PP) exhibit a photoluminescence (PL) band, which emits photons with an energy of around 4.3 eV when excited by photons with energies around 6.4 eV. The origin of this PL band has been assigned to α, β -unsaturated carbonyl. In this paper, the appearance of PL was examined for four kinds of polyolefin and four kinds of biodegradable polymers. As a result, it has become clear that all the polymers show a PL band with a PL excitation spectrum and a PL spectrum similar to those of the above-mentioned PL band in LDPE and PP. The decay profiles observed for these PL bands indicate that they are fluorescence. Furthermore, the intensity of the PL becomes weak for all the four polyolefin samples and the polylatic acid sample if ultraviolet photons were irradiated to the sample. Quantum chemical calculations carried out by assuming a model of α, β -unsaturated carbonyl have revealed that the PL originates in the π∗to π transition of electrons in the carbon-carbon double bond.

Modeling of oxidation process and property changes of ethylene-propylene-diene copolymer

Min, Daomin; Min, Daomin; Li, Shengtao; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi

IEEE Transactions on Dielectrics and Electrical Insulation23(1)p.537 - 5462016年02月-2016年02月 

DOIScopus

詳細

ISSN:10709878

概要:© 1994-2012 IEEE.The oxidation process induced in ethylene-propylene-diene (EPDM) copolymer by gamma irradiation was simulated by solving equations on chemical reactions and gas diffusion rates. As a result, distributions of oxidative products and gases and changes in material properties were clarified. All the oxidative products such as ketones, alcohols, and carboxylic acids, crosslinks between molecular chains, and chain scissions in EPDM increase with irradiation and they show concave spatial distributions inside the sample sheets. The simulation results demonstrates that EPDM becomes hard when it was irradiated by gamma rays and the increase in hardness is more significant at the surface of the sample sheet than its inside. Moreover, it was found that a low diffusion coefficient of oxygen in EPDM leads to the appearance of a clearer diffusion-limited regime of degradation. These simulation results are in good agreement with experimental results.

Effects of the structure and insulation material of a cable on the ability of a location method by FDR

Ohki, Yoshimichi; Ohki, Yoshimichi; Hirai, Naoshi

IEEE Transactions on Dielectrics and Electrical Insulation23(1)p.77 - 842016年02月-2016年02月 

DOIScopus

詳細

ISSN:10709878

概要:© 1994-2012 IEEE.The authors have demonstrated that the estimation of the precise locations of points in cables aged thermally or mechanically or by the irradiation of gamma rays is possible by a combination of frequency domain reflectometry and inverse fast Fourier transform. This paper examines how this ability of fault location depends on the type, structure, and insulation material of the cable, using several kinds of polymer insulated cables such as a triple core cable insulated with flame-retardant ethylene propylene diene copolymer, a dual core cable insulated with silicone rubber, a dual core cable insulated with crosslinked polyolefin (XLPO), a coaxial cylindrical cable insulated with low density polyethylene, and a flat cord insulated by polyvinyl chloride (PVC). As a result, for cables with lengths from 16 to 72 m, the maximum sensitivity is attained when the highest frequency of the inputted electromagnetic waves is 1.0 GHz or higher for coaxial cables, but around 300 to 800 MHz for dual or triple core cables. For the location attempt of the position heated by a heater, cables insulated with PVC give higher signal intensities than those insulated with XLPO.

Location attempts of a heated and irradiated portion in a silicone rubber insulated cable by frequency domain reflectometry and line resonance analysis

Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

IEEJ Transactions on Fundamentals and Materials136(9)p.553 - 5602016年01月-2016年01月 

DOIScopus

詳細

ISSN:03854205

概要:© 2016 The Institute of Electrical Engineers of Japan.Electric cables play important roles for supplying power and for transmitting information and control signals. Therefore, their degradation may cause a serious problem. Silicone rubber (SiR) is widely used for electrical insulation in safety-related cables in nuclear power plants. In this paper, the ability of locating a degraded portion in a duplex cable insulated with SiR was compared between a system based on frequency domain reflectometry (FDR) being developed by the authors and a commercially available system called line resonance analysis (LIRA). Reflecting the fact that the FDR system can expand the measurement frequency range, FDR shows a higher sensitivity and a better resolution than LIRA. However, both methods cannot detect the degradation of SiR before its further use becomes uncommendable.

周波数領域反射法によるケーブルの異常温度箇所の位置標定

山田 貴之;平井 直志;大木 義路;熊谷 進

電気学会研究会資料. EC, 電線・ケーブル研究会2013(1)p.39 - 442013年02月-2013年02月 

CiNii

局所熱・放射線同時劣化シリコーンゴム絶縁ケーブルの周波数領域反射測定法と線路共振解析法による劣化位置標定

平井 直志;大木 義路

電気学会論文誌A(基礎・材料・共通部門誌)136(9)p.553 - 5602016年-2016年

CiNii

詳細

ISSN:0385-4205

概要:

Electric cables play important roles for supplying power and for transmitting information and control signals. Therefore, their degradation may cause a serious problem. Silicone rubber (SiR) is widely used for electrical insulation in safety-related cables in nuclear power plants. In this paper, the ability of locating a degraded portion in a duplex cable insulated with SiR was compared between a system based on frequency domain reflectometry (FDR) being developed by the authors and a commercially available system called line resonance analysis (LIRA). Reflecting the fact that the FDR system can expand the measurement frequency range, FDR shows a higher sensitivity and a better resolution than LIRA. However, both methods cannot detect the degradation of SiR before its further use becomes uncommendable.

Diagnosis of surface degradation of flame-retardant ethylene propylene diene copolymer by scanning probe microscopy

Niki, Takayuki; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

Journal of Nuclear Science and Technology53(1)p.82 - 882016年01月-2016年01月 

DOIScopus

詳細

ISSN:00223131

概要:© 2015 Atomic Energy Society of Japan. All rights reserved.Most electric cables installed in nuclear power plants use organic polymers for their electrical insulation. Regarding this, degradation of the polymers could lead to fatal accidents. However, no truly reliable diagnostic methods that can detect the degradation of polymer insulation in electric cables have been established. Therefore, development of a reliable diagnostic method is very important. The present research shows that scanning probe microscopy can be a good tool to evaluate microscopic changes induced on the surface of flame-retardant ethylene propylene diene copolymer by its degradation.

Erratum: Modeling of oxidation process and property changes of ethylene-propylene-diene copolymer( IEEE Transactions on Dielectrics and Electrical Insulation (2016) 23:1 (537-546))

Min, Daomin; Min, Daomin; Li, Shengtao; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi

IEEE Transactions on Dielectrics and Electrical Insulation23(2)2016年04月-2016年04月 

DOIScopus

詳細

ISSN:10709878

Terahertz spectroscopic diagnosis of degradation of ethylene-propylene-diene copolymer

Ohki, Yoshimichi; Ohki, Yoshimichi; Kozai, Takuya; Komatsu, Marina; Hirai, Naoshi

Proceedings of the 2016 IEEE International Conference on Dielectrics, ICD 20162p.646 - 6492016年08月-2016年08月 

DOIScopus

詳細

概要:© 2016 IEEE.Flame-retardant ethylene-propylene-diene copolymer (FR-EPDM) with the same additives as those used in nuclear power plants was analyzed by terahertz (THz) and infrared (IR) absorption spectroscopy, before and after the irradiation by γ-rays. As a result, it has become clear that THz spectroscopy can indicate the degradation of the FR-EPDM samples better than IR spectroscopy. Namely, the THz spectroscopy can indicate the oxidation of the samples, which is difficult by IR spectroscopy.

Fault location in a cable for a nuclear power plant by frequency domain reflectometry

Ohki, Yoshimichi; Ohki, Yoshimichi; Hirai, Naoshi

CMD 2016 - International Conference on Condition Monitoring and Diagnosisp.36 - 392016年11月-2016年11月 

DOIScopus

詳細

概要:© 2016 IEEE.Cables installed in nuclear power plants are subjected to thermal burden and radioactive rays. Regarding this, if we want to monitor the integrity of a cable in a nuclear power plant continuously, we have to do measurements while the cable is heated and irradiated. In this research, we obtained frequency domain reflectometry signals for a 50-m long cable insulated with flame-retardant ethylene propylene diene copolymer (FR-EPDM) installed in an environment where heat and radiation were given simultaneously. Then, we separated signals originating in the degradation of the insulation from those due to heat and radiation. This result indicates that the separation of the signal arising from the degradation of insulation from other signals due to heat and radiation is in principle possible at least as far as FR-EPDM insulated cables are concerned.

Non-destructive diagnosis of degradation of silicone rubber by indenter modulus and scanning probe microscopy

Hanada, Shugo; Odaka, Daisuke; Yang, Liuqing; Yang, Liuqing; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

CMD 2016 - International Conference on Condition Monitoring and Diagnosisp.123 - 1262016年11月-2016年11月 

DOIScopus

詳細

概要:© 2016 IEEE.We aged silicone rubber, which is widely used for electrical insulation of cables in nuclear power plants under various conditions. The surface of each sample was measured by an indenter and a scanning probe microscope (SPM) for non-destructive diagnosis. As a result, it has become clear that the surface of silicone rubber becomes hard with the progress of degradation in both cases of thermal aging and simultaneous aging by heat and radiation. The indenter modulus shows a good correlation with the elongation at break (EAB). On the other hand, the delay of phase angle measured by SPM exhibits a rather low correlation with EAB. Through the results of thermal analyses, it seems that the thermal aging without radiation induces cross-linking first, which is followed by bond break. However, bond breakage seems predominant over cross-linking in the simultaneous aging with heat and radiation.

Chemiluminescence characteristics of FR-EPDM and SiR aged by concurrently-given heat and radiation

Ikeno, Risa; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP2016-Decemberp.853 - 8562016年12月-2016年12月 

DOIScopus

詳細

ISSN:00849162

概要:© 2016 IEEE.Flame-retardant ethylene propylene diene copolymer (FR-EPDM) and silicone rubber (SiR) were aged by heat with or without concurrent irradiation of gamma rays. For these samples, chemiluminescence (CL) and infrared absorption spectra were measured. Although the CL intensity decreases with an increase in total dose of gamma rays both in FR-EPDM and SiR, this negative dose-dependence is weaker in FR-EPDM than in SiR. This is reasonable, since CL appears when a substance is oxidized. Namely, the CL intensity becomes weak if the sample was already oxidized. While FR-EPDM is an organic polymer that can be oxidized easily, SiR is an inorganic polymer with siloxane bonds. Moreover, carbonyl groups appear when FR-EPDM is degraded, while SiR forms mainly a crosslinked structure by bridging two silicons by one oxygen when it is irradiated by gamma rays. Such differences in degradation mechanism between two insulating polymers are reflected on their CL properties.

Aging mechanism of silicone rubber by heat and gamma-rays

Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi; Hanada, Shugo; Miyamoto, Maki; Hirai, Naoshi; Yang, Liuqing; Yang, Liuqing

Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP2016-Decemberp.869 - 8722016年12月-2016年12月 

DOIScopus

詳細

ISSN:00849162

概要:© 2016 IEEE.The aging mechanism of silicone rubber, which is important for electrical insulation of cables, is examined from many aspects such as instrumental, chemical, electrical, and mechanical analyses. As a result, it has become clear that silicone rubber degrades by forming crosslinked structures via the formation of abundant siloxane bonds.

Dielectric spectroscopic analysis of degradation in ethylene-propylene-diene copolymer

Min, Daomin; Min, Daomin; Li, Shengtao; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi

IEEE Transactions on Dielectrics and Electrical Insulation23(6)p.3620 - 36302016年12月-2016年12月 

DOIScopus

詳細

ISSN:10709878

概要:© 2016 IEEE.Gamma-ray induced changes occurring in ethylene-propylene-diene copolymer (EPDM) were analyzed through its complex permittivity spectra. First, four different processes, namely, instantaneous polarization, hopping of ions, segmental relaxation, and dc conduction are found to contribute to the complex permittivity. By fitting the spectra to theoretical equations, it has become clear that the instantaneous polarization and ionic hopping become active by the irradiation, indicating that generation of oxidative products and mobile ions and occurrence of chain scission are induced by gamma rays. Furthermore, since both the thermal expansion and the contribution of the segmental relaxation to the permittivity become less with an increase in dose, it is assumed that crosslinking is induced by the gamma irradiation.

Space charge distributions in epoxy/MgO nanocomposites at various temperatures

Xie, Q.; Xie, Q.; Cheng, Y. H.; Hirai, N.; Ohki, Y.; Ohki, Y.; Ohki, Y.

ICHVE 2016 - 2016 IEEE International Conference on High Voltage Engineering and Application2016年12月-2016年12月 

DOIScopus

詳細

概要:© 2016 IEEE.The effect of addition of nano-sized magnesia fillers to epoxy resin on the distribution of space charges is examined at various temperatures from 40 to 200 °C. Although the spatial distribution of space charges in the sample varies depending on temperature and filler content, magnesia nanocomposites exhibit a smaller amount of homocharge near the cathode than the unfilled epoxy resin at 40 and 80 °C. At 120 and 140 °C, although the polarity of space charge in the vicinity of the cathode becomes positive or hetero, its amount becomes smaller with the increase in content of magnesia nanofillers. This finding agrees well with the fact that magnesia nanofillers effectively suppress the formation of space charge in low-density or crosslinked polyethylene. As another distinctive feature, it has become clear that the addition of magnesia nanofillers effectively suppresses carrier transport, especially at high temperatures.

Comparison of location abilities of degradation in a polymer-insulated cable between frequency domain reflectometry and line resonance analysis

Ohki, Yoshimichi; Ohki, Yoshimichi; Hirai, Naoshi

ICHVE 2016 - 2016 IEEE International Conference on High Voltage Engineering and Application2016年12月-2016年12月 

DOIScopus

詳細

概要:© 2016 IEEE.The ability of locating a degraded portion in a double-core cable insulated with silicone rubber (SiR) or in a coaxial cable insulated with low-density polyethylene (LDPE) was compared between a system based on frequency domain reflectometry (FDR) being developed by the authors and a commercially available system called line resonance analysis (LIRA). Both the FDR and the LIRA methods cannot detect the degradation of SiR before its further use becomes uncommend-able in a nuclear power plant. However, for location trials of the degraded portion in the LDPE coaxial cable, the FDR method showed a higher sensitivity and a better resolution than LIRA.

Aging of poly(ether ether ketone) by heat and gamma rays — Its degradation mechanism and effects on mechanical, dielectric and thermal properties

Yang, Liuqing; Yang, Liuqing; Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi; Hirai, Naoshi; Hanada, Shugo

Polymer Degradation and Stability142p.117 - 1282017年08月-2017年08月 

DOIScopus

詳細

ISSN:01413910

概要:© 2017 Elsevier Ltd In radiation research facility, where heat and radiation are two crucial factors inducing material degradation, highly stable materials are required. In the present work, various properties of poly(ether ether ketone) (PEEK) exposed to heat and gamma rays in air are instrumentally investigated. If PEEK is aged by heat and gamma irradiation in air, chemical bond scission, oxidation, crosslinking, and char formation occur as competing mechanisms. The temperature plays a decisive role in degradation, while the irradiation accelerates it. The mechanical properties deteriorate much earlier than the dielectric properties with the progress of aging. This means that the mechanical properties can be an important condition monitoring factor compared to the dielectric properties for PEEK-insulated apparatus or cables. If PEEK is aged severely, its electrical conductivity increases dramatically, whereas both real and imaginary parts of complex dielectric permittivity decrease, showing a marked contrast to many industrially important polymeric insulating materials.

Improved high-temperature dielectric property of epoxy resin composites with nano- and micro-sized magnesia fillers

Xie, Q.; Ohki, Y.; Hirai, N.; Cheng, Y. H.

2017 IEEE International Workshop on Integrated Power Packaging, IWIPP 20172017年05月-2017年05月 

DOIScopus

詳細

概要:© 2017 IEEE. Nano-sized magnesium oxide or magnesia has been reported to be useful for suppressing the space charge accumulation when it is added in epoxy resin. However, the addition of nano-magnesia to epoxy resin decreases the glass transition temperature (Tg) signficantly, which may limit industrial applications of magnesia/epoxy nanocomposites. In this work, nanomagnesia particles with an average size of 52 nm and micro-magnesia with an average size of 3.1 pm were mixed in a commercially available bisphenol-A epoxy resin. The weight ratio of nano- and micro-fillers in each composite was changed, while the total content of the two fillers was fixed at 5 weight%. As a result, it has become clear that the addition of micro-sized magnesia fillers to magnesia/epoxy nanocomposites recovers Tg back to its original high temperature. Then, a dc electric field of 30 kV/mm was applied to the samples for 20 minutes at various temperatures from 40 to 200 °C and space charge distributions were measured by the pulsed electro-Acoustic method. The results show that space charge accumulates in both vicinities of the cathode and the anode with the same polarities as those of the nearby electrodes when the temperature is 80 °C or below. However, space charges become hetero and are observed only in the vicinity of the cathode at 140 °C and above. These homocharges and heterocharges become very small when the weight content of nano-sized fillers increases, which is industrially very important. Both complex dielectric permittivity and electrical conductivity also decrease with the increase in the content of nanofillers.

Identification of antioxidants in polymeric insulating materials by terahertz absorption spectroscopy

Kozai, Takuya; Kaneko, Takuya; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

Polymer Degradation and Stability147p.284 - 2902018年01月-2018年01月 

DOIScopus

詳細

ISSN:01413910

概要:© 2017 The Authors For the purpose of using organic polymeric materials for electrical insulation, various additives such as antioxidants are added to prevent degradation or oxidative decomposition of the polymers. Therefore, it is desirable that we can identify antioxidants added in polymers by instrument analyses. In this research, terahertz absorption spectroscopy was conducted for nine kinds of antioxidants. The spectroscopy was also conducted for sheets of low-density polyethylene, to which each antioxidant had been added with different contents. As a result, it has become clear that each antioxidant has its own specific spectrum. In addition, for most antioxidants, the absorption intensity is proportional to the content of antioxidant added in LDPE. However, several absorption peaks change their spectral shapes when the antioxidant is in LDPE.

Terahertz absorption spectra of antioxidants in insulating polymers

Kozai, Takuya; Kaneko, Takuya; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

Proceedings of the International Symposium on Electrical Insulating Materials1p.61 - 642017年10月-2017年10月 

Scopus

詳細

概要:Terahertz absorption spectra were measured for nine kinds of antioxidants. The spectra were also measured for lowdensity polyethylene sheets that contain each antioxidant with different contents. As a result, a fingerprint spectrum appears for each antioxidant, from which the antioxidants become distinguishable and their contents can be estimated.

Insulation performance of safety-related cables for nuclear power plants under simulated severe accident conditions

Minakawa, Takefumi; Minakawa, Takefumi; Ikeda, Masaaki; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi

Proceedings of the International Symposium on Electrical Insulating Materials2p.716 - 7192017年12月-2017年12月 

DOIScopus

詳細

概要:© 2017 Institute of Electrical Engineers of Japan. All rights reserved. To examine electrical insulation behavior of cables under severe accident environmental conditions, safety-related low voltage cables used as severe accident management equipment were subjected to two tests that simulated two environments: 1) at 155 oC, which is the simulated highest assumed temperature when proper accident management measures are taken, 2) at 200 oC, which is the maximum durable temperature of a primary containment vessel. In addition, electrical insulation resistance was measured for the cables during steam exposure in the two tests. As a result, all the cables passed the acceptance criteria of the tests. The minimum volume resistivity of the cables during the test at 155 oC was around 10 8 Ωm, confirming that the cables have a sufficient insulation performance. On the other hand, the minimum volume resistivity during the severer test at 200 oC was around 10 5 Ωm due to the increase in leak current.

Correlation between indenter modulus and elongation-at-break observed for four electrical insulating polymers

Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

Proceedings of the International Symposium on Electrical Insulating Materials2p.753 - 7562017年12月-2017年12月 

DOIScopus

詳細

概要:© 2017 Institute of Electrical Engineers of Japan. All rights reserved. The correlation between degradation-induced changes in two important indicators of mechanical properties, namely elongation at break (EAB) and indenter modulus (IM), is examined for flame-retardant ethylene propylene rubber (FR-EPR), silicone rubber (SiR), flame-retardant crosslinked polyethylene (FR-XLPE), and XLPE. The samples were degraded by heat or concurrently by heat and radiation. In the case that the polymers become hard after they were degraded, the two indicators show a good correlation. However, if they become brittle, their correlation is not good. Regarding this, their correlation is good in SiR, while it is not good in FR-XLPE and XLPE. In FR-EPR, the correlativity changes, depending on the aging condition and presumably its additives.

Terahertz absorption spectroscopy of poly(ether ether ketone)

Kaneko, Takuya; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

Proceedings of the International Symposium on Electrical Insulating Materials2p.539 - 5422017年12月-2017年12月 

DOIScopus

詳細

概要:© 2017 Institute of Electrical Engineers of Japan. All rights reserved. The crystallinity of sheets of poly(ether ether ketone) (PEEK) was changed by thermal treatments conducted at 295 oC for various periods and their terahertz (THz) and Fouriertransform infrared absorption (FT-IR) spectra were obtained. As a result, it has been confirmed that an absorption peak appears at around 3.5 THz in the sheet samples that exhibit clear X-ray diffraction patterns at 20= 18.8, 20.8, 22.8, and 28.8o. In contrast, no obvious sample-dependent changes were observed in FT-IR spectra. The absorption at around 3.5 THz shows a shift in frequency to a degree proportional to the crystallinity. Its maximum intensity is also in proportion to the crystallinity. These results indicate that the absorption at 3.62 THz has a close relation with the crystallinity of PEEK This in turn means that the THz absorption spectroscopy can be used for estimating the crystallinity of PEEK.

Effects of addition of MgO fillers with various sizes and co-addition of nano-sized SiO2fillers on the dielectric properties of epoxy resin

Yanashima, Ryosuke; Hirai, Naoshi; Ohki, Yoshimichi; Ohki, Yoshimichi

Proceedings of the International Symposium on Electrical Insulating Materials2p.650 - 6532017年12月-2017年12月 

DOIScopus

詳細

概要:© 2017 Institute of Electrical Engineers of Japan. All rights reserved. Complex permittivity (ϵ r ' and ϵ r "), conductivity (σ), and glass transition temperature (T g ) were measured for composites of epoxy resin and MgO fillers with various sizes in a wide temperature and frequency range. The effect of coaddition of nano-sized SiO 2 was also examined. It has become clean that T g decreases by the addition of MgO fillers, and its decrement becomes more with a decrease in filler size. Moreover, T g decreases if the silica nanofillers are co-added. However, all the three important parameters for electrical insulation ability of polymers, namely ϵ r ', ϵ r ", and σ, decrease with the decrease in size of MgO fillers or by the addition of silica nanofillers at high temperatures and low frequencies. This is a very astonishing result, since it seems reasonable that a polymer with a high T g should have a better insulating ability. Probably, the above-mentioned results indicate that the charge transport becomes more difficult, presumably resulting from the suppression of molecular motion with the decrease in size of MgO fillers and by the co-addition of SiO 2 nanofillers. This indicates that the suppression of molecular motion becomes very strong if the filler size is small, making the carrier transport difficult even in polymers with low T g .

Degradation of silicone rubber analyzed by instrumental analyses and dielectric spectroscopy

Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi; Hirai, Naoshi; Min, Daomin; Min, Daomin; Yang, Liuqing; Yang, Liuqing; Li, Shengtao

Minerals, Metals and Materials SeriesPart F11p.107 - 1162018年01月-2018年01月 

DOIScopus

詳細

ISSN:23671181

概要:© The Minerals, Metals & Materials Society 2018. Silicone rubber (SiR) was gamma irradiated at 125, 145 and 185 °C or thermally aged at 220, 250 and 280 °C and the resultant changes in performance were evaluated. It has become clear from instrumental analyses that crosslinking via oxidation of silicon atoms and chain scission are induced by gamma rays. Furthermore, from the temperature dependence of real relative permittivity at high frequencies, the thermal expansion coefficient was found to become smaller with the increase in dose. These results can be understood well by the chemical and structural changes in SiR induced by the degradation.

Successful detection of insulation degradation in cables by frequency domain reflectometry

Ohki, Yoshimichi; Ohki, Yoshimichi; Ohki, Yoshimichi; Hirai, Naoshi

Minerals, Metals and Materials SeriesPart F11p.77 - 852018年01月-2018年01月 

DOIScopus

詳細

ISSN:23671181

概要:© The Minerals, Metals & Materials Society 2018. We have succeeded in detecting the degradation of cable’s polymeric insulation well before its continual use becomes risky. Degradation of organic polymers is mainly caused by oxidation if the ambience around the cable contains oxygen. When organic polymers are oxidized, polar carbonyl groups are formed, by which the permittivity is increased. This in turn decreases the characteristic impedance of a polymer-insulated cable. If we inject electromagnetic waves in a very wide frequency range into the cable and measure the ratio of reflected power to injected power, the information on the effects of the characteristic impedance changes is included in the frequency spectra of the ratio. If we do inverse Fourier transform, we can convert the data to a time domain. Therefore, we can know the degraded portion by multiplying the velocity of electromagnetic waves in the cable.

特許

整理番号:807

電気絶縁材料及びそれを用いた絶縁電線、通信用ケーブル、電気部品(日本)

大木 義路, 平井 直志

特願2008- 79669、特開2009-238411

整理番号:1326

絶縁電線又はケーブルの温度変化箇所の位置標定方法(日本)

大木 義路, 平井 直志, 山田 貴之

特願2012-146311、特開2014- 10027、特許第5763594号

整理番号:1446

絶縁電線又はケーブルの歪み量変化箇所の位置標定方法(日本)

大木 義路, 平井 直志

特願2013-208460、特開2015- 72217

外部研究資金

科学研究費採択状況

研究種別:挑戦的萌芽研究

超広帯域誘電・吸収分光による高分子の物性評価と絶縁劣化診断

2012年-2013年

研究分野:電子・電気材料工学

配分額:¥4030000

研究種別:基盤研究(C)

化学発光測定による生分解性高分子の劣化評価

2011年-2013年

研究分野:電子・電気材料工学

配分額:¥5590000

研究種別:基盤研究(B)

高分子・無機ナノコンポジットを用いた高性能絶縁材料の開発

2011年-2013年

研究分野:電子・電気材料工学

配分額:¥19630000

研究種別:基盤研究(B)

各種生分解性高分子の誘電特性支配因子の解明

2008年-2010年

研究分野:電子・電気材料工学

配分額:¥18330000

研究種別:萌芽研究

テラヘルツ分光によるポリマーナノコンポジットの優れた誘電特性出現機構の解明

2007年-2008年

研究分野:電子・電気材料工学

配分額:¥3100000

研究種別:基盤研究(B)

オールソリッド変電所構築のための機能傾斜材料の開発

2002年-2004年

研究分野:電子・電気材料工学

配分額:¥13000000

研究種別:

高分子絶縁材料中の不純物が絶縁特性に与える影響の解明と直流ケーブル用材料の開発

配分額:¥2200000

学内研究制度

特定課題研究

有機高分子絶縁材料中の電荷分布の実時間測定

2000年度

研究成果概要: 本研究は、架橋ポリエチレンケーブル中の空間電荷形成機構を空間電荷分布の実時間測定により解明し、架橋ポリエチレンケーブルが直流長距離送電に利用できる可能性を示すことを目的としている。有機高分子絶縁体の試料としてポリエチレンを使用し... 本研究は、架橋ポリエチレンケーブル中の空間電荷形成機構を空間電荷分布の実時間測定により解明し、架橋ポリエチレンケーブルが直流長距離送電に利用できる可能性を示すことを目的としている。有機高分子絶縁体の試料としてポリエチレンを使用し、架橋剤分解残渣である、アセトフェノン、αメチルスチレン、クミルアルコールそれぞれを浸漬させた試料を用いて、これらの残渣がポリエチレン中における空間電荷形成に及ぼす影響を測定した。 アセトフェノン、αメチルスチレンの場合は、浸漬試料が陽極に接触している場合は、浸漬、未浸漬試料の界面において浸漬試料から未浸漬試料中へ正電荷の移動が確認された。一方、浸漬試料が陰極に接触している場合は、浸漬、未浸漬試料の界面において浸漬試料から未浸漬試料中へ電荷の移動はなく、界面に負電荷が蓄積されるのみであった。1層の浸漬試料においては空間電荷は測定できなかった。これに対して、片面のみにアセトフェノン、αメチルスチレンを塗布した1層の試料では、塗布面が陽極側のときのみ正電荷の移動が確認された。これらの電荷は伝導電流測定より、導電率の増加によるものであることが分かった。これより、アセトフェノン、αメチルスチレンは、電荷移動を促進する作用があると判断できる。 クミルアルコールの場合には、前者の場合とは対称的に、浸漬試料が陽極に接触している場合は、電極、浸漬試料の界面に正電荷が蓄積し、浸漬、未浸漬試料の界面に負電荷が蓄積した。また、浸漬試料から未浸漬試料中へ負電荷の移動は確認されなかった。浸漬試料が陰極に接触している場合は、電極、浸漬試料の界面に負電荷が蓄積し、浸漬、未浸漬試料の界面において正電荷が蓄積した。また、浸漬試料から未浸漬試料中へ電荷の移動はなかった。伝導電流測定より浸漬試料の導電率の増加は確認されたが、界面に蓄積された電荷の極性の違いの原因は明確でない。また、1層の浸漬試料においては、電極と試料の界面に、接触している電極と同極性の電荷が蓄積されていることが測定できた。これは、クミルアルコールが存在すると電荷はその付近でトラップされることを示すものである。 つまり、アセトフェノン、αメチルスチレンは、ポリエチレン中において電荷移動を促進する作用を持つのに対し、クミルアルコールは、電荷をトラップして空間電荷を蓄積させる作用があることを見いだした。このことより、架橋ポリエチレン中よりその架橋剤分解残渣であるクミルアルコールのみを除去できれば、架橋ポリエチレンには空間電荷は形成されないことになり、架橋ポリエチレンケーブルが直流長距離送電に利用できる可能性を示した。

高分子絶縁材料中の不純物が絶縁特性に与える影響の解明と直流ケーブル用材料の開発

2001年度

研究成果概要: 本研究は、架橋ポリエチレンケーブル中の空間電荷形成機構を空間電荷分布の実時間測定により解明し、架橋ポリエチレンケーブルが直流長距離送電に利用できる可能性を示すことを目的としている。有機高分子絶縁体の試料としてポリエチレンを使用し... 本研究は、架橋ポリエチレンケーブル中の空間電荷形成機構を空間電荷分布の実時間測定により解明し、架橋ポリエチレンケーブルが直流長距離送電に利用できる可能性を示すことを目的としている。有機高分子絶縁体の試料としてポリエチレンを使用し、架橋剤分解残渣である、アセトフェノン、αメチルスチレン、クミルアルコールそれぞれを浸漬させた試料を用いて、これらの残渣がポリエチレン中における空間電荷形成に及ぼす影響を測定した。 アセトフェノン、αメチルスチレンの場合は、浸漬試料と未浸漬試料で構成された2層誘電体では、浸漬試料―未浸漬試料の界面に浸漬試料が接している電極と同極性の電荷が蓄積した。クミルアルコールの場合は、前2者とは対照的に、浸漬試料―未浸漬試料の界面に浸漬試料が接している電極と逆極性の電荷が蓄積した。アセトフェノン、αメチルスチレンにおける電荷蓄積の原因は、伝導電流測定より(導電率/誘電率)の不連続性によるものであると考えられる。これより、アセトフェノン、αメチルスチレンは、電荷移動を促進する作用があると判断できる。一方、クミルアルコールの場合は、伝導電流測定より浸漬試料の導電率の増加は確認されたが、浸漬試料―未浸漬試料の界面に蓄積された電荷の極性が前2者とは違うことより、電荷蓄積の原因は、(導電率/誘電率)の不連続性によるものではなく、クミルアルコールは注入電荷をトラップする作用を持っていると考えられる。 そこで、注入電荷トラップの原因を明確にするため、化学薬品の化学構造とくにカルボニル基、水酸基、ベンゼン環に注目し、それらの化学基の少なくとも1つ以上を含む薬品を使用して空間電荷分布測定を行った。架橋剤分解残渣である3種類の薬品に加えて、ベンゼン環を持つドデシルベンゼン、水酸基とカルボニル基を持つグリセリンモノステアラート、ベンゼン環と水酸基を持つジブチルヒドロキシルトルエンを使用した。空間電荷分布測定の結果、浸漬試料―未浸漬試料の界面電荷は、ドデシルベンゼンの場合は、アセトフェノン、αメチルスチレンと同極性の電荷、グリセリンモノステアラート、ジブチルヒドロキシルトルエンはクミルアルコールと同極性の電荷の蓄積が得られた。この結果より明らかなことは、界面における蓄積電荷の極性と化学構造の関係において水酸基を持つ薬品がポリエチレン中に存在すれば注入電荷をトラップする作用があると考えられることである。 つまり、アセトフェノン、αメチルスチレンは、ポリエチレン中において電荷移動を促進する作用を持つのに対し、クミルアルコールは、電荷をトラップして空間電荷を蓄積させる作用があり、その電荷トラップの原因は水酸基であることを見いだした。

現在担当している科目

科目名開講学部・研究科開講年度学期
加速器実習大学院先進理工学研究科2019集中(春・秋学期)