Faculty Profiles - TOKUMITSU Katsuhisa

Papers - TOKUMITSU Katsuhisa

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Relationship between Dynamic Viscoelasticity and Amorphous Structural Changes Associated with Enthalpy Relaxation in Polystyrene Injection Moldings Reviewed

Tao K., Yamada K., Hatano A., Takeshita H., Higashi S., Kago K., Kuwashiro S., Hirano H., Tokumitsu K.

Nihon Reoroji Gakkaishi 50 ( 2 ) 181 - 187 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Nihon Reoroji Gakkaishi

In this study, we investigated the relationship between the amorphous structural changes associated with enthalpy relaxation and the Heat distortion temperature (HDT) in polystyrene injection moldings. It was clarified that the longer heat treatment time, the more enthalpy relaxation progressed. Also, an extrapolation glass transition temperature (Tig) increased by heat treatment. In addition, long-time heat treatment caused the high-temperature shift of the storage modulus (E') decrease temperature near glass transition temperature (Tg). Since the increase in Tig and the high-temperature shift of E' decrease temperature correlated with the enthalpy relaxation, they can be closely related to the enthalpy relaxation. Thus, we considered that the segment motion of polymer chain was suppressed as the enthalpy relaxation progressed. At long-term heat treatment, the enthalpy relaxation and the HDT were correlated. Furthermore, density increased by the heat treatment, and the increase in density also correlated with the progress of the enthalpy relaxation. Therefore, we considered that the polymer chains densely packed along with the enthalpy relaxation. As the result of polymer chains being densely packed, the segment motion of polymer chains near Tg can be suppressed and the HDT increased.

DOI： 10.1678/rheology.50.181

Scopus

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Effects of Copolymer Composition on Phase Transition Behavior and Mobility of Mesogenic Group for Side-Chain Liquid Crystalline-Amorphous Random Copolymers Reviewed

Takeshita H., Kanazawa A., Tokumitsu K.

Nihon Reoroji Gakkaishi 50 ( 2 ) 189 - 195 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Nihon Reoroji Gakkaishi

Liquid crystalline (LC) phase behavior, higer-order structure, and mobility of mesogenic groups were investigated by using DSC, polarizing optical microscopy, small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD) and dielectric relaxation spectroscopy (DRS) for random copolymers composed of cyanobiphenyl-based side-chain LC and the amorphous components with various compositions. LC phase behavior of the copolymers was systematically changed depending on the mole fraction of the LC component, fLC11. When fLC11 > 0.75, incorporation of small fraction of the amorphous component resulted in slightly highered LC order and almost unchanged LC-isotropic transition temperature, Tiso. This may be because the copolymerization of the amorphous component canceled the inherent frustration in the LC homopolymer, which comes from the dissidence between lateral distance of adjacent nearest mesogenic groups in the smectic LC phase and that of the side-chains on mainchain. According to the DRS measurements, incorporation of the amorphous component also accelerated the molecular mobility of the mesogenic groups, which may be also related to the relaxation of the internal conformational frustration because of the dissidence.

DOI： 10.1678/rheology.50.189

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85130366850&origin=inward

The relationship between the change in dynamic viscoelasticity by heat treatment and heat resistance in polystyrene moldings Reviewed

TAO K., YAMADA K., HIGASHI S., TAKESHITA H., TOKUMITSU K.

Zairyo/Journal of the Society of Materials Science, Japan 70 ( 1 ) 11 - 16 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Zairyo/Journal of the Society of Materials Science, Japan

The mechanism of heat resistance improvement of polystyrene injection moldings by heat treatment was studied. The increase in the Heat Distortion Temperature (HDT) by heat treatment was confirmed. Meanwhile, in dynamic viscoelasticity measurement, the shoulder of the loss tangent (tanδ) appeared at 60 to 90°C in untreated specimen. In the heat-treated specimen, the shoulder at that temperature range disappeared. Further, when the frequency dependence of tanδ was evaluated, it was found that the mobility of molecular chain in the main dispersion did not change by the heat treatment, and the mobility in the temperature range where the tanδ shoulder appeared was reduced by the heat treatment. By differential scanning calorimetry, the progress of enthalpy relaxation by heat treatment was confirmed. Also, excellent correlation existed between the progress of enthalpy relaxation and the disappearance of the tanδ shoulder by heat treatment. Since the tanδ shoulder disappeared in the heat-treated specimen in which relaxation has progressed yet, it was considered that the tanδ shoulder was caused by molecular motion accompanying the relaxation phenomenon. Addisionally, as well as the disappearance of the tanδ shoulder, the increase in HDT correlated with the progress of enthalpy relaxation by heat treatment. In conclusion, with the progress of the relaxation by the heat treatment, the tanδ shoulder disappeared, and thereby the molecular mobility at 60 to 90°C decreasesed. Since the HDT of the untreated specimen was 78°C, the HDT increased due to the decrease in the molecular mobility below 78°C by heat treatment. Thus, it is considered that the increase in HDT correlated with the progress of enthalpy relaxation by heat treatement.

DOI： 10.2472/jsms.70.11

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85100734586&origin=inward

A study on Photo- and Thermal- degradation of Polyethylene in addition of Polysilane Invited Reviewed

Hideya Suzuki / Hiroki Takeshita / Katsuhisa Tokumitsu

Seikei-Kakou 32 ( 12 ) 428 - 433 2020.7

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Japan Society of Polymer Processing Participation form：Joint(The main charge)

In this study, photo-and thermal-degradation behaviors of high density polyethylene (HDPE) with/without polymethylphenylsilane (PMPS) were investigated. There is a tendency that the modulus of HDPE with/without PMPS exposed to UV irradiation increased with exposure time, although the elongation at break decreased with exposure time. In particular, the ductile-brittle transition occurs earlier by the addition of PMPS. This result suggests that PMPS can accelerate photo-degradation of HDPE. As for the thermal-degradation, the oxidation induction time (OIT) of HDPE with PMPS is also shorter than that of neat one. Moreover, the activation energy of the oxidation of HDPE decreased with the PMPS content, indicating that PMPS also accelerates the thermal-degradation. Although the mechanism to accelerate the photo-and thermal-degradation of HDPE has not been cleared yet, it can be deduced that the pro-oxidant process caused by accelerating autoxidation with silyl radical generated by PMPS during UV irradiation and/or heattreatment occurred in HDPE.

DOI： 10.4325/seikeikakou.32.428

フルオレン修飾セルロースナノファイバーにより補強したポリアミドの特性評価 Reviewed

杉本雅行，山田昌宏，荘所大策，佐藤嘉計，徳満勝久

成形加工学会誌 32 ( 2 ) 63 - 67 2020.2

Reinforcement of Polyamide 6/66 with 9,9-bis(aryl)fluorene-Modified Cellulose Nanofiber Reviewed

Masayuki Sugimoto, Masahiro Yamada, Hirokazu Sato, and Katsuhisa Tokumitsu

Polymer Journal 2019.8

新規ポリオレフィン材料の低温力学物性と分子運動性に関する研究 Reviewed

梅本叡史，徳満勝久，竹下宏樹，竹内大介，小坂田耕太郎

材料 68 ( 1 ) 47 - 53 2019.1

側鎖1,2ジオール結合を有するエチレンビニルアルコール共重合体とナイロン6-66ブレンド物の高圧水素耐性と分散状態の関係 Reviewed

澁谷光夫，徳満勝久，竹下宏樹，住野翔郷，西村伸，藤原広匡

材料 68 ( 1 ) 34 - 41 2019.1

熱融着法による籾殻活性炭複合材料の物性評価研究 Reviewed

宮原和美，徳満勝久，竹下宏樹，脇坂　博之

マテリアルライフ学会誌 30 ( 3 ) 52 - 63 2018.10

The effect of Interfacial Polysilane Coating on Heat Fusion Properties of Polypropylene Reviewed

Katsuhisa Tokumitsu, Asuka Hayashi, Sakiko Fukunishi, Kazuhumi Kohno, Masami Okamoto

日本レオロジー学会誌 46 ( 3 ) 123 - 130 2018.6

Crystallization Behavior of Polyvinyl Alcohol with 1,2-Diol Side-Chains Reviewed International journal

M. Shibutani, T. Yamamoto, K. Inoue, K. Tokumitsu

International Polymer Processing 33 ( 2 ) 234 - 244 2018.5

低温環境における積層フィルムの経年変化予測に関する研究 Reviewed

湯浅明子，島岐宏，徳満勝久

マテリアルライフ学会誌 30 ( 1 ) 11 - 17 2018.2

ポリエチレン系材料のアルコール中における環境応力破壊に関する研究 Reviewed

ティホングニュングエン，田中隆，石黒翔太，梅木慎吾

成形加工学会誌 29 ( 8 ) 302 - 308 2017.8

カルド修飾CNF/PLAコンポジット材料の力学的・熱的物性評価研究(II) Reviewed

桂田慎也，佐藤嘉和，徳満勝久，山田昌宏，杉本雅行

日本レオロジー学会誌 45 ( 1 ) 25 - 32 2017.1

UHMWPE/HDPE系材料における極低温力学物性改質技術の研究-インフレーションフィルム積層法の検討 Reviewed

井口愛子，徳満勝久，大平英治

材料 66 ( 1 ) 29 - 34 2017.1

カルド修飾CNF/PLAコンポジット材料の力学的・熱的物性評価研究 Reviewed

寺倉弘祐，徳満勝久，山田昌宏，杉本雅行

日本レオロジー学会誌 44 ( 1 ) 39 - 45 2016.1

ポリシラン添加によるPP/nano-Sio2複合材料の物性改質効果に関する研究 Reviewed

福井雄哉，竹下宏樹，山下義裕，徳満勝久，福西佐季子，高野一史，伊藤賢志

材料試験技術 60 ( 3 ) 152 - 158 2015.7

カルド系材料添加ポリ乳酸の結晶化挙動に関する研究 Reviewed

徳満勝久，松浦拓也，川崎真一，田代孝二

材料 64 ( 1 ) 1 - 6 2015.1

Influence of Electron Beam Irradiation on the Mechanical and Thermal Properties of Polypropylene/Polyamide6 Blends Reviewed International journal

Shigeya Nakamura, Katsuhisa Tokumitsu, Tohru Yamaguchi

Journal of Applied Polymer Science 130 ( 6 ) 4318 - 4326 2013.12

A Study on the Mechanical Properties of Poly(Butylene Terephthalete) Containing Some Elastomer Additives with Reactive Compatibilizers Reviewed

Katsuhisa Tokumitsu, Ken-ichi Nishizaka

Nihon Reoroji Gakkaishi (Journal of the Society of Rheology, Japan) 41 ( 3 ) 145 - 150 2013.6

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Papers - TOKUMITSU Katsuhisa