Updated on 2024/04/03

写真a

 
ISHIDA Takato
 
Organization
Institute for Advanced Research Designated assistant professor
Graduate School of Engineering Designated assistant professor
Title
Designated assistant professor
Contact information
メールアドレス
External link

Degree 1

  1. Ph. D. in Engineering ( 2022.3   Hokkaido University ) 

Research Interests 10

  1. Degradation of polymers

  2. Non-equilibrium aging simulation

  3. Degradation analysis of polymers

  4. Soft Material

  5. Multi-scale Material Degradation Analysis / Diagnosis

  6. Building and Construction Materials

  7. Material Morphology / Higher Order Structure / Molecular Architecture

  8. Material Degradation (Ultraviolet-ray, heat, moisture)

  9. Material Science

  10. Thermosetting polymer

Research Areas 6

  1. Nanotechnology/Materials / Polymer materials

  2. Natural Science / Biophysics, chemical physics and soft matter physics

  3. Nanotechnology/Materials / Green sustainable chemistry and environmental chemistry

  4. Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Building structures and materials

  5. Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Building structures and materials  / Building and Construction Materials

  6. Nanotechnology/Materials / Polymer materials  / Material Life of Polymeric Materials

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Research History 7

  1. Institute for Advanced Research, Nagoya University   YLC Designated Assistant Professor

    2024.4

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  2. Nagoya University   Graduate School of Engineering Materials Physics   Research fellow

    2022.5 - 2024.3

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  3. Japan Society for the Promotion of Science   Research fellow PD

    2022.4 - 2024.3

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  4. Hokkaido University   Graduate School of Engineering

    2021.2 - 2022.3

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  5. National Institute of Advanced Industrial Science and Technology

    2020.10 - 2021.3

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  6. National Institute of Advanced Industrial Science and Technology

    2020.7 - 2022.3

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  7. Japan Society for the Promotion of Science

    2019.4 - 2022.3

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Education 3

  1. Hokkaido University   Graduate School of Engineering   Division of Solid Waste, Resources and Geoenvironmental Engineering

    2019.4 - 2022.3

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    Country: Japan

    Notes: Ph.D. candidate

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  2. École nationale supérieure d'arts et métiers   Processes and Engineering in Mechanics and Materials

    2020.1 - 2020.3

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    Country: France

    Notes: Guest Ph.D. student

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  3. The University of Tokyo   The Graduate School of Engineering   Department of Architecture

    2017.4 - 2019.3

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    Country: Japan

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Professional Memberships 7

  1. The Society of Rheology, Japan

    2022.10

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  2. THE SOCIETY OF RUBBER SCIENCE AND TECHNOLOGY, JAPAN

    2022.10

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  3. 日本建築仕上学会

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  4. 日本建築学会

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  5. 高分子分析研究懇談会

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  6. 高分子学会

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  7. マテリアルライフ学会

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Awards 8

  1. 研究奨励賞

    2023.7   マテリアルライフ学会   ラジカルを介した自動酸化機構を組み入れた高分子劣化のメソスケールシミュレーション

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  2. Best Presentation award

    2023.5   The Society of Rheology, Japan   Coarse-grained Molecular Dynamics Modeling of Oxidative Degradation of Polymers

    Takato Ishida

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  3. Outstanding Poster Award

    2021.10   THE JAPAN SOCIETY FOR ANALYTICAL CHEMISTRY  

    Takato Ishida

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  4. Prize of pioneering a new field

    2021.2   Science Academy Tsukuba  

    Takato Ishida

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  5. Research Award

    2020.8  

    Takato Ishida

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  6. Excellence Master's Thesis Award

    2019.8   Architectural Institute of Japan  

    Takato Ishida

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  7. Excellence Master's Thesis Award

    2019.3  

    Takato Ishida

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  8. Excellence Student Award

    2019.3  

    Takato Ishida

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Papers 27

  1. Modeling for Heterogeneous Oxidative Aging of Polymers Using Coarse-Grained Molecular Dynamics Reviewed

    Takato Ishida, Yuya Doi, Takashi Uneyama, Yuichi Masubuchi

    Macromolecules   Vol. 56 ( 21 ) page: 8474 - 8483   2023.11

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    This study presents a coarse-grained molecular dynamics simulation model to
    investigate the process of oxidative aging in polymers. The chemical aging
    effect is attributed to the auto-oxidation mechanism, which is initiated by
    radicals, leading to the chain scission and crosslinking of polymer chains. In
    this study, we integrate a thermal oxidation kinetic model in the oxygen excess
    regime into the Kremer-Grest model, thereby enabling a reactive coarse-grained
    molecular dynamics simulation to capture the process of oxidative degradation.
    Our simulation reveals that when the timescale of the characteristic reaction
    step of oxidative degradation is shorter than the longest relaxation time of
    polymer chains, the scission sites exhibit spatial heterogeneity. This
    innovative simulation model possesses the potential to enhance our
    comprehension of polymer aging phenomena, thus making noteworthy contributions
    to the realm of polymer science and degradation chemistry.

    DOI: 10.1021/acs.macromol.3c01708

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  2. Network Degradation Assessed by Evolved Gas Analysis–Mass Spectrometry Combined with Principal Component Analysis (EGA–MS–PCA): A Case of Thermo-Oxidized Epoxy/Amine Network Reviewed

    Takato Ishida, Ryoma Kitagaki, Yogarajah Elakneswaran, Junji Mizukado, Hideyuki Shinzawa, Hiroaki Sato, Hideaki Hagihara, Ryota Watanabe

    Macromolecules   Vol. 56 ( 3 ) page: 883 - 891   2023.2

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    To study the degradation of thermosetting polymers, we apply a novel method to simultaneously study the chemical structural changes and network topology: evolved gas analysis-mass spectrometry combined with principal component analysis (EGA-MS-PCA). This technique was applied to thermo-oxidative aging of an epoxy/amine network. The signals of various pyrolyzates remain overlapped in the complicated EGA-MS profiles. The key fragments of thermally evolved gases derived from the components of the network are effectively selected by PCA from the complicated EGA-MS profiles. EGA-MS-PCA provides information on the network structure: (i) the oxidized fraction of cross-links (i.e., chemically damaged cross-links), (ii) the relative quantification of unbonded chains, and (iii) the formation of dangling chains. The proposed technique can simultaneously characterize chemical degradation and network structural properties. This characterization technique can be utilized as a generally applicable tool for determining the structural durability of thermosetting polymers.

    DOI: 10.1021/acs.macromol.2c02383

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  3. Review of Rheology in Cement-Based Materials and Its Application to 3D Printing Using Concrete Reviewed

    Takato Ishida, Kiyofumi Nakada

    NIHON REOROJI GAKKAISHI   Vol. 51 ( 1 ) page: 1 - 8   2023

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:SOC RHEOLOGY, JAPAN  

    This review briefly summarizes introductory understandings of concrete rheology and applications in which rheology plays an important role. A mixture of cement and water is the rheological material classified as dispersed systems involving chemical reactions, and it has been considered the most challenging research subject in the field of rheology. This review introduces the most crucial chemical admixture for fresh concrete controlling rheological properties (so-called superplasticizer) after summarizing the fundamental knowledge of concrete rheology. In addition, recent research trends on 3D printing using concrete, riddled with rheological challenges, are introduced.

    DOI: 10.1678/rheology.51.1

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  4. Accelerated Aging Test Modeling for Polycarbonate: Effects of Light Source Reviewed

    Takato Ishida, Ryoma Kitagaki

    MACROMOLECULAR SYMPOSIA   Vol. 405 ( 1 )   2022.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:WILEY-V C H VERLAG GMBH  

    This work addresses to propose a model to reproduce accelerated aging results for polycarbonate. Four accelerated aging conditions are studied, including several light sources. In this study, aging behaviors are monitored by the yellowing index. Obtained simulations are well-tracked the aging data for four accelerated aging conditions. Besides, the features of accelerating environments by a phase plane plot are challenged to visualize.

    DOI: 10.1002/masy.202100211

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  5. In-situ infrared cure monitoring combined with two-trace two-dimensional (2T2D) correlation analysis to elucidate the matrix–filler interaction of nanocomposites: Case of thermosetting urethane/silica nanospheres Reviewed

    Takato Ishida, Ryota Watanabe, Hideyuki Shinzawa, Junji Mizukado, Hideaki Hagihara, Ryoma Kitagaki, Yogarajah Elakneswaran

    Polymer Testing   Vol. 112   page: 107587 - 107587   2022.8

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier {BV}  

    A novel technique, in-situ infrared (IR) cure monitoring coupled with two-trace two-dimensional (2T2D) correlation analysis, is developed to probe the property-enhancement mechanism of a newly developed thermosetting nanocomposite comprising an acrylic-urethane network (AUN) and silica nanospheres (SNS). The IR spectra were collected in real-time during the curing process at 100 degrees C. We employ the 2T2D correlation analysis to identify the spectral variations of the interfacial interaction. The curing reaction initially proceeds throughout the sample solution. After the network percolation, the unreacted sites react near the SNS surface and yield additional hydrogen-bonded C = O groups that interact with the surface silanol groups. The matrix-filler interactions play a key role in enhancing the hardness and thermal stability of the AUN/SNS nanocomposites by restricting the mobility of the polymer molecules. The proposed technique provides sequential mechanisms in the curing process and a picture of the interfacial interaction for the thermosetting nanocomposite system.

    DOI: 10.1016/j.polymertesting.2022.107587

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  6. Thermal aging of acrylic-urethane network: Kinetic modeling and end-of-life criteria combined with mechanical properties Reviewed

    Takato Ishida, Emmanuel Richaud, Matthieu Gervais, Alain Gaudy, Ryoma Kitagaki, Hideaki Hagihara, Yogarajah Elakneswaran

    Progress in Organic Coatings   Vol. 163   page: 106654 - 106654   2022.2

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    This study addresses the multiscale analysis of acrylic urethane networks (AUN). To establish the kinetic model for predicting AUN oxidation, this study considered the pure thermal oxidation of AUN at 160, 180, and 200 degrees C. Chemical changes were monitored using infrared spectroscopy. These indicated the presence of an imide, presumably generated from the oxidation of CH2 at the alpha-position of nitrogen. On the macromolecular and macroscopic scales, oxidation was shown to induce predominant crosslinking, leading to a drop in toughness (i. e., embrittlement). The novel kinetic model of AUN thermal aging was developed from a mechanistic scheme previously established for polyamide 11, by adding some extra paths of thermolytic alkyl radical formation, oxidative N-H bonds decomposition and coupling of aminyl radicals.

    DOI: 10.1016/j.porgcoat.2021.106654

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  7. Role of moisture in photo-ageing -macromolecular architecture evolution of acrylic-urethane network Reviewed

    Takato Ishida, Ryoma Kitagaki, Hideaki Hagihara, Yogarajah Elakneswaran

    Polymer Testing   Vol. 96   page: 107123 - 107123   2021.4

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    In this work, the role of moisture in photo-ageing was discussed for the case of an acrylic-urethane network. Ageing behaviours were characterised by Fourier transform infra-red spectroscopy, positron annihilation lifetime spectroscopy, sol-gel analysis, and differential scanning calorimetry. Two common features between dry and wet photo-ageing, namely, decrease in the mean free volume and increase in the glass transition temperature were observed as photo-oxidation progressed. The characteristics of the final internal structure of the wet photo-aged sample differed from those of the dry photo-aged sample. Although the dry photo-aged samples suggested network densification due to extensive crosslinking formation, wet photo-ageing led to an inhomogeneous structure wherein the average molar mass between crosslinks (at a scale of several nanometres) increased and some domains crosslinked at the sub-nanoscale. Considering the physical (plasticisation) and chemical (hydrolysis) effects induced by water, a possible mechanism for the evolution of the macromolecular architecture was proposed for photo-ageing in dry and wet environments.

    DOI: 10.1016/j.polymertesting.2021.107123

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  8. A study of molecular architectural dynamics of crosslinked urethane during photo-aging by two-dimensional infrared correlation spectroscopy Reviewed

    Takato Ishida

    Polymer Degradation and Stability   Vol. 179   page: 109242 - 109242   2020.9

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    The molecular architecture changes of crosslinked urethane during photo-oxidation was investigated by Fourier transform infrared spectroscopy (FTIR) in combination with two-dimensional (2D) correlation analysis. The 2D correlation FTIR spectroscopy provided insight into molecular architectural dynamics during photo-aging, where the sequential order of peak changes was determined upon perturbation with photo-aging. Photo-oxidation was monitored from the decrease in the peak intensity at 1537 cm(-1) (attributed to the urethane group) and the generation of the hydrogen bonded C=O groups at 1698 cm(-1) immediately after urethane decomposition. Several notable peaks appeared (1712,1650, and 1750 cm(-1)) in the later stages, which were attributed to the free photo-oxidative product. In summary, photo oxidation involved a cleavage of urethane crosslink and generation of end groups that formed hydrogen bonds with surrounding hydrogen bonding sites. Further degradation of the free photo products was observed likely because of the small number of accessible hydrogen bonding sites due to the increasing heterogeneity of the internal structure. (C) 2020 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.polymdegradstab.2020.109242

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  9. Challenges in prediction of significant structural changes during photochemical “degelation” of acrylic-urethane network Reviewed

    Takato Ishida, Ryoma Kitagaki, Hideaki Hagihara, Yogarajah Elakneswaran

    Polymer   Vol. 186   page: 122035 - 122035   2020.1

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier {BV}  

    Structural changes induced by photo-aging have significant influence on material properties. The prediction of the period prior to the onset of significant morphological changes is useful in determining material service lifetime. We assume "degelation" to be the starting point of significant morphological change during photo-aging. Herein, we demonstrated the relationship between such time and the "degelation" phenomenon for an acrylic-urethane network polymer. We also derived a "degelation" theory considering network imperfections, e. g. dangling chains and looping chains. This provides a more accurate representation of reactive curing polymers widely used in industries. Lastly, we estimated the "imperfection degree" by comparing the number of elastically active chains obtained from a swelling experiment with the theoretically derived number. In this system, samples may originally possess approximately 10% network imperfection and it influences on the degelation period in aging process. Our study may potentially contribute to a more accurate prediction of the onset of significant structural change.

    DOI: 10.1016/j.polymer.2019.122035

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  10. Temperature dependence of structural alteration by ultraviolet irradiation in acrylic-urethane coatings studied by positron annihilation spectroscopy and solvent swelling behavior Reviewed

    Ishida, T., Kitagaki, R., Yamane, S., Hagihara, H.

    Polymer Degradation and Stability   Vol. 162   page: 85 - 93   2019.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCI LTD  

    The structural alteration of acrylic-urethane coatings, induced by photo-aging, and its temperature dependence, was investigated using positron annihilation lifetime spectroscopy and solvent swelling experiments. The results revealed a slight structural alteration due to photo-aging at 20 degrees C. On the other hand, a significant structural alteration occurred due to photo-aging at 60 degrees C, which resulted in a decrease in the pore size and total pore volume. To study the mechanism of such morphological changes, infrared spectra were measured before and after aging the samples. The results revealed the breakage of the urethane crosslink points and the generation of various photo-products including peroxide species that can form hydrogen bonds. This indicates the foundation of new physical and chemical crosslinks (different from the initial urethane linkage). Based on the chemical modifications, probable mechanisms of the internal morphological changes are proposed. Moreover, the changes are mainly due to an enhancement in the chain-mobility, due to the destruction of the polymer network and an increase in the inter-chain interactions. The results of this study reveal that significant internal structural alterations can occur after sufficient damage to the initial network structure. The proposed explanation is reasonable in relation to the temperature dependence of photo-induced structural alterations, and with respect to the molecular mobility and reaction ratio of photo-oxidation. (C) 2019 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.polymdegradstab.2019.02.007

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  11. Temperature dependent photodegradation on urethane coatings for building materials in a low relative humidity environment Reviewed

    Takato Ishida, Ryoma Kitagaki

    Kobunshi Ronbunshu   Vol. 75 ( 3 ) page: 265 - 274   2018

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Society of Polymer Science  

    Organic coatings for building exterior walls are attracting a lot of attention because of the requirement for long-term usage of buildings and other constructs. Polyurethane (PU) has been commonly applied on building exterior walls. UV irradiation tests were carried out in a custom made apparatus at low relative humidity (< 10%) and several surface temperatures. For irradiated samples, IR and Raman spectra were measured to study change of chemical structure. Irradiated samples did not yellow on exposure and we could not observe an increase of double bond groups (C=C, C=O). In terms of temperature dependent degradation reactions, the Photo-Fries reaction seemingly does not depend on temperature, whereas Norrish type reactions are promoted by higher temperature. Moreover, we investigated the relationship between aggregate-state and change of elastic modulus, in early stages, it shows a better correlation between them than in later stages.

    DOI: 10.1295/koron.2017-0082

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  12. Cover Image Reviewed

    Keigo Enomoto, Takato Ishida, Yuya Doi, Takashi Uneyama, Yuichi Masubuchi

    International Journal for Numerical Methods in Fluids     2024.2

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    DOI: 10.1002/fld.5258

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  13. Extension of moving particle simulation by introducing rotational degrees of freedom for dilute fiber suspensions Reviewed

    Keigo Enomoto, Takato Ishida, Yuya Doi, Takashi Uneyama, Yuichi Masubuchi

    International Journal for Numerical Methods in Fluids   Vol. 96 ( 2 ) page: 125 - 137   2024.2

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    We develop a novel Moving Particle Simulation (MPS) method to accurately
    reproduce the motion of fibers floating in sheared liquids. In conventional MPS
    schemes, if a fiber suspended in a liquid is represented by a one-dimensional
    array of MPS particles, it is entirely aligned to the flow direction due to the
    lack of shear stress difference between fiber-liquid interfaces. To address
    this problem, we employ the micropolar fluid model to introduce rotational
    degrees of freedom into the MPS particles. The translational motion of liquid
    and solid particles and the rotation of solid particles are calculated with the
    explicit MPS algorithm. The fiber is modeled as an array of micropolar fluid
    particles bonded with stretching and bending potentials. The motion of a single
    rigid fiber is simulated in a three-dimensional shear flow generated between
    two moving solid walls. We show that the proposed method is capable of
    reproducing the fiber motion predicted by Jeffery's theory being different from
    the conventional MPS simulations.

    DOI: 10.1002/fld.5235

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    Other Link: http://arxiv.org/pdf/2301.03818v1

  14. Gas diffusion in cement pastes: An analysis using a fluctuating diffusivity model Reviewed

    Fumiaki Nakai, Takato Ishida

    Construction and Building Materials   Vol. 407   page: 133411 - 133411   2023.12

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    Authorship:Last author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.conbuildmat.2023.133411

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  15. Phantom-Chain Simulations for the Effect of Node Functionality on the Fracture of Star-Polymer Networks Reviewed

    Yuichi Masubuchi, Yuya Doi, Takato Ishida, Naoyuki Sakumichi, Takamasa Sakai, Koichi Mayumi, Kotaro Satoh, Takashi Uneyama

    Macromolecules   Vol. 56 ( 23 ) page: 9359 - 9367   2023.9

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    The influence of node functionality (f) on the fracture of polymer networks
    remains unclear. While many studies have focused on multi-functional nodes with
    f>4, recent research suggests that networks with f=3 exhibit superior fracture
    properties compared to those with f=4. To clarify this discrepancy, we
    conducted phantom chain simulations for star-polymer networks varying f between
    3 and 8. Our simulations utilized equimolar binary mixtures of star branch
    prepolymers with a uniform arm length. We employed a Brownian dynamics scheme
    to equilibrate sols and induce gelation through end-linking reactions. We
    prevented the formation of odd-order loops owing to the binary reaction and
    second-order loops algorithmically. We stored network structures at various
    conversion ratios ({\phi}_c) and minimized energy to reduce computation costs
    induced by structural relaxation. We subjected the networks to stretching until
    fracture to determine stress and strain at break and work for fracture,
    {\epsilon}_b, {\sigma}_b, and W_b. These fracture characteristics are highly
    dependent on {\phi}_c for networks with small f but relatively insensitive for
    those with large f. Thus, the networks with small f exhibit greater fracture
    properties than those with large f at high {\phi}_c, whereas the opposite
    relationship occurs at low {\phi}_c. We analyzed {\epsilon}_b, {\sigma}_b, and
    W_b concerning the cycle rank {\xi} and the broken strand fraction {\phi}_bb.
    We found {\epsilon}_b, {\sigma}_b/{\phi}_bb, and W_b/{\phi}_bb monotonically
    decrease with increasing {\xi}, and the data for various f and {\phi}_c
    superpose with each other to draw master curves. These results imply that the
    mechanical superiority of the networks with small f comes from their smaller
    {\xi} that gives higher {\epsilon}_b, {\sigma}_b/{\phi}_bb, and W_b/{\phi}_bb
    than the networks with large f.

    DOI: 10.1021/acs.macromol.3c01291

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    Other Link: http://arxiv.org/pdf/2307.09832v1

  16. A Multi-Chain Slip-Spring Model without the Slip-Spring Degeneracy Reviewed International journal

    Yuichi Masubuchi, Yuya Doi, Takato Ishida, Takashi Uneyama

    Nihon Reoroji Gakkaishi   Vol. 51 ( 4 ) page: 211 - 217   2023.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Society of Rheology, Japan  

    <p>In the multi-chain slip-spring, the dynamics of Rouse chains connected by virtual springs called slip-springs that hop along the chain are considered. Although this approach has been proven to reproduce entangled polymer dynamics efficiently, the settings of the artificially introduced slip-springs should be carefully examined. In this study, we discussed the effect of the slip-spring degeneracy by limiting the number of anchored slip-springs on each Rouse bead to zero and one. According to the altered slip-spring statistics, we derived the compensation potential to eliminate the artifact of slip-springs on the chain statistics. With this potential, we performed numerical simulations. The results demonstrated that although we reasonably retain the Gaussian chain statistics, the dynamics deviate from the established entangled polymer dynamics because of the significant slow-down in the chain motion induced by the correlation between different slip-springs. The observed deceleration can be explained by the fact that the movement of slip-springs can be cast into an asymmetric exclusion process.</p>

    DOI: 10.1678/rheology.51.211

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  17. Preparation and characterization of two-dimensional sheet-shaped poly(methyl methacrylate) synthesized via γ-ray polymerization in nanoclay template Reviewed

    Yuya Doi, Mitsuo Hara, Takahiro Seki, Atsushi Takano, Takato Ishida, Takashi Uneyama, Yuichi Masubuchi

    Polymer Journal   Vol. 55 ( 9 ) page: 957 - 965   2023.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    Two-dimensional sheet-shaped poly(methyl methacrylate) (2d-PMMA) with crosslinking only in the two-dimensional direction was synthesized via planar polymerization of MMA monomer in montmorillonite (MMT) nanolayers by using ?-ray irradiation, and the samples obtained were characterized. Size-exclusion chromatography with a multi-angle light scattering (SEC-MALS) measurements of the obtained sample showed bimodal peaks: a main peak with a longer elution time and an apparent molecular weight M-w,M-app and radius of gyration R-g in tetrahydrofuran (THF) similar to those for linear PMMA samples, and a subpeak with a shorter elution time and M-w,M-app and R-g evidently lower than those for the linear PMMA samples. This result indicated that polymers with moderate branching and crosslinking were contained in the subpeak. Atomic force microscopy (AFM) observation of the sample showed the presence of sheet-shaped molecules with a height of ca. 0.6 nm, corresponding to the thickness of one MMA monomer, and a width of several to several tens of nanometers, showing a broad distribution in molecular width. The subpeak portion was isolated via SEC fractionation, and its AFM observation showed thin circular disk-shaped molecules with relatively uniform size (i.e., a width of several tens of nanometers). However, in these molecules, two types of molecular heights (i.e., 0.6 and 1.2 nm) were identified. This result indicated that MMA monomers were filled as two layers within one MMT interlayer, and the polymerization reaction proceeded in that state. The similarity in the molecular size of 2d-PMMA observed via AFM and SEC-MALS was confirmed. These results demonstrated that the desired sheet-shaped polymers were obtained through the above synthesis and fractionation process.

    DOI: 10.1038/s41428-023-00795-4

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    Other Link: https://www.nature.com/articles/s41428-023-00795-4

  18. Increase in rod diffusivity emerges even in Markovian nature Reviewed

    Fumiaki Nakai, Martin Kröger, Takato Ishida, Takashi Uneyama, Yuya Doi, Yuichi Masubuchi

    Physical Review E   Vol. 107 ( 4 ) page: 044604   2023.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    Rod-shaped particles embedded in certain matrices have been reported to
    exhibit an increase in their center of mass diffusivity upon increasing the
    matrix density. This increase has been considered to be caused by a kinetic
    constraint in analogy with tube models. We investigate a mobile rod-like
    particle in a sea of immobile point obstacles using a kinetic Monte Carlo
    scheme equipped with a Markovian process, that generates gas-like collision
    statistics, so that such kinetic constraints do essentially not exist. Even in
    such a system, provided the particle's aspect ratio exceeds a threshold value
    of about 24, the unusual increase in the rod diffusivity emerges. This result
    implies that the kinetic constraint is not a necessary condition for the
    increase in the diffusivity.

    DOI: 10.1103/PhysRevE.107.044604

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    Other Link: http://arxiv.org/pdf/2301.02394v2

  19. Phantom Chain Simulations for the Fracture of Energy-Minimized Tetra- and Tri-Branched Networks Reviewed

    Yuichi Masubuchi, Yuya Doi, Takato Ishida, Naoyuki Sakumichi, Takamasa Sakai, Koichi Mayumi, Takashi Uneyama

    MACROMOLECULES   Vol. 56 ( 5 ) page: 2217 - 2223   2023.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER CHEMICAL SOC  

    Effects of branch functionality on mechanical properties of polymer networks are yet to be fully elucidated, although multi-functional approaches have been mainly attempted. For instance, Fujiyabu et al. [Sci. Adv. 2022, 8, abk0010] recently reported that polymer networks made from tri-branch prepolymers exhibit superior mechanical properties to tetra-branch analogues. Although they attribute the difference to stretch-induced crystallization observed in tri-branch poly (ethylene glycol) networks, the mechanism still needs to be clarified. In this study, we performed coarse-grained molecular simulations to extract the effect of branch functionality. The prepolymers were replaced by bead-spring phantom chains, and gelation was simulated by a Brownian dynamics scheme. We subjected the resultant networks to energy minimization and uniaxial stretch by introducing breakage for elongated segments. In the stress-strain relation thus obtained, stress and strain at the break were larger for tri-branch networks than that for tetra-branch analogues, consistent with the experiment. The superiority of tri-branch networks is observed in a wide range of the conversion ratio in gelation, molecular weights of prepolymers, and polymer concentrations. The result implies that the mechanical superiority of tri-branch networks to tetra-branch ones is due to a fundamental structural difference generated during gelation.

    DOI: 10.1021/acs.macromol.3c00047

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  20. Fluctuating diffusivity emerges even in binary gas mixtures Reviewed

    Fumiaki Nakai, Yuichi Masubuchi, Yuya Doi, Takato Ishida, Takashi Uneyama

    PHYSICAL REVIEW E   Vol. 107 ( 1 ) page: 014605   2023.1

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    Diffusivity in some soft matter and biological systems changes with time, called the fluctuating diffusivity. In this work, we propose a novel origin for fluctuating diffusivity based on stochastic simulations of binary gas mixtures. In this system, the fraction of one component is significantly small, and the mass of the minor component molecule is different from that of the major component. The minor component exhibits fluctuating diffusivity when its mass is sufficiently smaller than that of the major component. We elucidate that this fluctuating diffusivity is caused by the time scale separation between the relaxation of the velocity direction and the speed of the minor component molecule.

    DOI: 10.1103/PhysRevE.107.014605

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    Other Link: http://arxiv.org/pdf/2207.05424v2

  21. Stress Tensor of Single Rigid Dumbbell by Virtual Work Method Reviewed

    Takashi Uneyama, Tatsuma Oishi, Takato Ishida, Yuya Doi, Yuichi Masubuchi

    NIHON REOROJI GAKKAISHI   Vol. 50 ( 4 ) page: 313 - 322   2022

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SOC RHEOLOGY, JAPAN  

    We derive the stress tensor of a rigid dumbbell by using the virtual work method. In the virtual work method, we virtually apply a small deformation to the system, and relate the change of the energy to the work done by the stress tensor. A rigid dumbbell consists of two particles connected by a rigid bond of which length is constant (the rigid constraint). The energy of the rigid dumbbell consists only on the kinetic energy. Also, only the deformations which do not violate the rigid constraint are allowed. Thus we need the dynamic equations which are consistent with the rigid constraint to apply the virtual deformation. We rewrite the dynamic equations for the underdamped SLLOD-type dynamic equations into the forms which are consistent with the rigid constraint. Then we apply the virtual deformation to a rigid dumbbell based on the obtained dynamic equations. We derive the stress tensor for the rigid dumbbell model from the change of the kinetic energy. Finally, we take the overdamped limit and derive the stress tensor and the dynamic equation for the overdamped rigid dumbbell. We show that the Green-Kubo type linear response formula can be reproduced by combining the stress tensor and the dynamic equation at the overdamped limit.

    DOI: 10.1678/rheology.50.313

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    arXiv

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    Other Link: http://arxiv.org/pdf/2205.09374v1

  22. Mathematical Modeling of Outdoor Natural Weathering of Polycarbonate: Regional Characteristics of Degradation Behaviors Reviewed

    Takato Ishida, Ryoma Kitagaki

    Polymers   Vol. 13 ( 5 ) page: 820 - 820   2021.3

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:MDPI AG  

    Many natural exposure sites have been developed to ensure the reliability of materials intended for outdoor use. However, the effects of local climate on aging have not been completely understood. This study aimed to elucidate the regional characteristics of natural aging. Non-stabilized and stabilized polycarbonates were monitored in terms of their appearance (yellowing and loss of gloss) during natural weathering at five exposure sites (Tokyo, Kagoshima, Okinawa, Florida, and Arizona) in conjunction with climate fluctuation for up to 24 months. Three approaches were employed to characterize the natural aging behaviors: (i) modeling the rate function of degradation, (ii) evaluating the contribution ratio of individual degradational factors, and (iii) estimating the “synchronicity” by cross-correlation analysis with the climate dataset. The aging rates were the highest in Arizona and lowest in Kagoshima among the five exposure sites. First, prediction curves were constructed from the degradation rate function (variables: UV irradiation, temperature, and humidity), and these curves were found to agree well with the measured aging behaviors. Second, the exposure data in Arizona demonstrated strong temperature dependence, while those in Okinawa and Florida had stronger dependence on UV irradiation compared to other sites. Lastly, the synchronicity between UV irradiation and temperature was the highest in Arizona and lowest in Kagoshima, which can explain the significantly faster deterioration in Arizona and the slow deterioration in Kagoshima.

    DOI: 10.3390/polym13050820

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  23. Intrinsic Differences on the Photodegradation Mechanisms between Pigmented and Non-Pigmented Coatings Determined by Multi-Scale Analysis Reviewed

    T. Ishida, R. Kitagaki, H. Hagihara, Y. Elakneswaran

    XV International Conference on Durability of Building Materials and Components. eBook of Proceedings     2020.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:CIMNE  

    DOI: 10.23967/dbmc.2020.087

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  24. Free Volume Hole Size Evaluation of Polymeric Coatings and its Degradation Analysis using Positron Annihilation Lifetime Spectroscopy Invited Reviewed

    Takato Ishida, Ryoma Kitagaki, Hideaki Hagihara

    Journal of Japan Coating Technology Association   Vol. 55 ( 12 ) page: 488 - 495   2020.8

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    CiNii Books

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  25. Morphology Changes and Fillers Migration in Urethane Composites during Thermal Degradation Reviewed

    Atsuki Tanifuji, Takato Ishida, Ryoma Kitagaki

    Current Topics and Trends on Durability of Building Materials and Components - Proceedings of the 15th International Conference on Durability of Building Materials and Components, DBMC 2020     page: 177 - 182   2020

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    Polyurethane composite coatings are frequently applied to strengthen the barrier properties of various construction materials such as wood, metal and concrete. The changes of color and glossiness of the composite coatings for building materials proceeds more slowly than that of polyurethane because of containing fillers and several types of additives. However, the most critical barrier properties have not been studied directly based on the difference from the degradation mechanism of polyurethane coatings. Additionally, the difference in thermal and UV degradation mechanisms of coatings is not clear in the existing studies dealing with conventional accelerated weathering tests and outdoor exposure tests. Therefore, the behavior of the filler contained in the coatings was observed using an oven to accelerate thermal degradation. The chemical analysis of the coating surface by XPS and the analysis of the images and elemental mappings by SEM-EDS were carried out, and the mechanism of degradation progress was investigated. In addition, the temperature dependency of the degradation was studied in changing the heating temperature. It was suggested that polymer and fillers interact in promoting mass transfer at the same time as the thermal degradation reaction consequently.

    DOI: 10.23967/dbmc.2020.100

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  26. Multi-scale Analysis of Photo-degradation for Urethane-based Coating - Characterization of Morphological Changes and its Impact on Macroscopic Properties Induced by Aging-

    Takato Ishida

        2019.3

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  27. Temperature Dependency of Photodegradation Mechanisms by Using Humidity and Temperature Controlled UV irradiation equipment ―Physical and Chemical Properties Change on Urethane Coatings for Building Material― Invited Reviewed

    Takato Ishida, Ryoma Kitagaki

      Vol. 53 ( 4 ) page: 114 - 121   2018

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MISC 20

  1. Accelerated Weathering Test of Polymers Exhibiting Self-Decelerating Degradation Behavior: A Consideration of the Validity of Comparing Degradation Status between Different Light Sources for Determining the Schwarzschild Parameter

    石田崇人, 北垣亮馬

    日本建築仕上学会大会学術講演会研究発表論文集   Vol. 2023   2023

  2. EGA-MS-PCA法による架橋高分子の劣化解析-エポキシ樹脂の熱酸化劣化-

    石田崇人, 北垣亮馬, エラクネスヨガラジャ, 水門潤治, 新澤英之, 佐藤浩昭, 萩原英昭, 渡邉亮太

    日本ゴム協会研究発表講演会講演要旨   Vol. 2023   2023

  3. Prediction of natural weathering of polycarbonate: Regional characteristics of aging behaviors and effect of “synchronicity” between UV irradiance and temperature

    石田崇人, 北垣亮馬

    日本建築仕上学会大会学術講演会研究発表論文集   Vol. 2021   2021

  4. Simple Estimation Method of the Risk of Condominium Repair Fund Shortage part 1 Improving Location Identification Procedure

    北垣亮馬, 相尚寿, 石田崇人

    日本建築仕上学会大会学術講演会研究発表論文集   Vol. 2021   2021

  5. Simple Estimation Method of the Risk of Condominium Repair Fund Shortage part 2 Applying the Method to Areas along Several Railway Lines in Tokyo

    相尚寿, 北垣亮馬, 石田崇人

    日本建築仕上学会大会学術講演会研究発表論文集   Vol. 2021   2021

  6. Prediction Model of Polycarbonate Aging in outdoor exposure

    石田崇人, 北垣亮馬

    日本建築学会大会学術講演梗概集・建築デザイン発表梗概集(CD-ROM)   Vol. 2021   2021

  7. ゲル化理論を逆に用いた光劣化に伴うウレタン架橋樹脂の大規模構造変化時期予測モデルの検討

    石田崇人, 北垣亮馬, エラクネスヨガラジャ, 萩原英昭

    日本ゴム協会研究発表講演会講演要旨   Vol. 2021   2021

  8. 水分が光劣化挙動に与える影響-架橋ウレタンのマルチスケール劣化解析-

    石田崇人, 北垣亮馬, ELAKNESWARAN Yogarajah, 萩原英昭

    マテリアルライフ学会研究発表会   Vol. 31st   2020

  9. 11037 マンションの修繕積立金の分布に関する基礎的研究 (2018年度版)

    谷口 誠, 石田 崇人, 北垣 亮馬

    情報システム技術   ( 2019 ) page: 85 - 88   2019.7

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  10. 1656 クリア塗膜と有色塗膜の間での紫外線劣化シナリオの本質的差異

    北垣 亮馬, 石田 崇人

    材料施工   ( 2019 ) page: 1311 - 1312   2019.7

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  11. 架橋ウレタンの光劣化に伴う内部組織構造変化シナリオとその起源

    石田崇人, 北垣亮馬, 萩原英昭

    マテリアルライフ学会研究発表会   Vol. 30th   2019

  12. 1166 解体工事における構造種類別・工程別の歩掛・平米作業単価と規模効果に関する調査

    金 志訓, 北垣 亮馬, 石田 崇人

    材料施工   ( 2018 ) page: 331 - 332   2018.7

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  13. 1697 温冷繰返しによる発泡プラスチック系断熱材(XPS)の水分浸透の分析

    久永 真子, 北垣 亮馬, 石田 崇人, 輿石 直幸, 宮内 博之, 山本 大地

    材料施工   ( 2018 ) page: 1393 - 1394   2018.7

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  14. 1667 ポリウレタン樹脂系塗膜の濡れ性に対する顔料濃度の影響

    石田 崇人, 北垣 亮馬

    材料施工   ( 2018 ) page: 1333 - 1334   2018.7

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  15. 陽電子寿命測定及び膨潤度測定を用いた紫外線劣化を受けるウレタンクリア塗膜の微視的構造変化の検出

    石田崇人, 北垣亮馬, 萩原英昭

    マテリアルライフ学会研究発表会   Vol. 29th   2018

  16. マンションの修繕積立金の資金繰り逼迫性の空間分布構造に関する基礎的研究

    北垣亮馬, 石田崇人, 長根乃愛, 片桐由希子

    日本建築学会大会学術講演梗概集・建築デザイン発表梗概集(CD-ROM)   Vol. 2018   2018

  17. 紫外線劣化を受けるウレタンクリア塗膜の空隙構造変化メカニズムに関する研究

    石田崇人, 北垣亮馬

    高分子学会予稿集(CD-ROM)   Vol. 67 ( 2 )   2018

  18. 陽電子寿命測定及び膨潤度測定を用いた紫外線劣化によるウレタン塗膜の微視的構変化の温度依存性

    石田崇人, 北垣亮馬, 萩原英昭

    高分子分析討論会講演要旨集   Vol. 23rd   2018

  19. ウレタンクリア塗膜の光劣化機構の温度依存性及び膨潤度測定を用いた劣化によるモルフォロジー変化に関する一考察

    石田崇人, 北垣亮馬

    日本建築仕上学会大会学術講演会研究発表論文集   Vol. 2018   2018

  20. ウレタンクリア塗膜の光劣化機構の温度依存性と物性変化メカニズムの検討

    石田崇人, 北垣亮馬

    高分子学会予稿集(CD-ROM)   Vol. 67 ( 1 )   2018

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KAKENHI (Grants-in-Aid for Scientific Research) 8

  1. Rheology of large particle dispersions

    Grant number:23K17940  2023.6 - 2026.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Challenging Research (Exploratory)

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  2. Modeling of Shrinkage Behavior of Polymers

    Grant number:23H01142  2023.4 - 2026.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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  3. Simulation of Deterioration of Reinforced Concrete Structural Members with Polymer Coating on the Surface

    2023.4 - 2024.3

    Takato Ishida

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  4. Evaluation of Long-Term Durability of Real Concrete Structures -Stochastic Small Molecule Diffusion Simulation in Concrete with Polymer Barrier Layer on the Surface

    Grant number:EX23502  2023.4 - 2024.3

    Takato Ishida, Nakai Fumiaki

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  5. Multi-scale Simulation of Polymer Degradation: From Molecular Dynamics to Macroscopic Properties

    Grant number:22J00300  2022.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows  Grant-in-Aid for JSPS Fellows

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  6. Elucidation of temperature- humidity dependence of photo-aging mechanisms for polymeric coatings on building use and accompanying macroscopic properties change

    Grant number:19J20126  2019.4 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows  Grant-in-Aid for JSPS Fellows

    Takato Ishida

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  7. Elucidation of degradation mechanisms in ultraviolet exposed coatings of building usage under well-controlled temperature/humidity conditions

    2018.4 - 2019.3

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  8. Temperature and humidity dependence of multi-scale degradation mechanisms of polymeric materials for building and construction usage

    2018.4 - 2019.3

    Hokkaido university 

    Takato Ishida

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    Authorship:Principal investigator 

    Grant amount:\500000 ( Direct Cost: \500000 )

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