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      Molecular Dynamics Simulations of Molecular Diffusion Equilibrium and Breakdown Mechanism of Oil-Impregnated Pressboard with Water Impurity

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          Abstract

          The water molecule migration and aggregation behaviors in oil-impregnated pressboard are investigated by molecular dynamics simulations in combination with Monte Carlo molecular simulation technique. The free energy and phase diagram of H 2O-dodecylbenzene (DDB) and H 2O-cellulose mixtures are calculated by Monte Carlo technique combined with the modified Flory-Huggins model, demonstrating that H 2O molecules can hardly dissolved with infinitesimal content in cellulose system at temperature lower than 650 K, based on which the oil/cellulose layered structure with water impurity representing three-phase coexistence in oil-impregnated pressboard are modeled and performed for molecular dynamics. The molecular dynamics of H 2O/DDB/cellulose three-phase mixture simulating oil-paper insulating system with H 2O impurity indicates that DDB molecules can thermally intrude into the cellulose-water interface so as to separate the water phase and cellulose fiber. The first-principles electronic structure calculations for local region of H 2O/DDB interface show that H 2O molecules can introduce bound states to trap electrons and acquire negative charges, so that they will obtain sufficient energy from applied electric field to break DDB molecular chain by collision, which are verified by subsequent molecular dynamics simulations of H 2O /DDB interface model. The electric breakdown mechanism under higher than 100 kV/m electric field is presented based on the further first-principles calculations of the produced carbonized fragments being dissolved and diffusing in DDB phase. The resulted broken DDB fragments will introduce impurity band between valence and conduction bands of DDB system, evidently decreasing bandgap as to that of conducting materials in their existence space. The conductance channel of these carbonized DDB fragments will eventually be formed to initiate the avalanche breakdown process by the cycle-feedback of injected charge carriers with carbonized channels.

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          ReaxFF:  A Reactive Force Field for Hydrocarbons

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            Molecular Dynamics Simulations of Bulk Native Crystalline and Amorphous Structures of Cellulose

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              Molecular dynamics simulation of polymer liquid and glass. II. Short range order and orientation correlation

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                Author and article information

                Journal
                Polymers (Basel)
                Polymers (Basel)
                polymers
                Polymers
                MDPI
                2073-4360
                16 November 2018
                November 2018
                : 10
                : 11
                : 1274
                Affiliations
                [1 ]Heilongjiang Provincial Key Laboratory of Dielectric Engineering, School of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin 150080, China; yiguan_hrbust@ 123456126.com (Y.G.); minghe_chi@ 123456126.com (M.-H.C.); qgchen_hrbust@ 123456126.com (Q.-G.C.); xinlao_wei@ 123456126.com (X.-L.W.)
                [2 ]Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, China
                Author notes
                [* ]Correspondence: sunweifeng@ 123456hrbust.edu.cn ; Tel.: +86-15846592798
                Article
                polymers-10-01274
                10.3390/polym10111274
                6401954
                7a0cabb9-6818-4a6c-812e-e2f676b22186
                © 2018 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 30 October 2018
                : 15 November 2018
                Categories
                Article

                oil-impregnated pressboard,molecular dynamics simulation,phase equilibrium,electric breakdown

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