Effect of cellulose nanocrystals on the performance of oil-immersed transformer insulating paper

Chen, Qijie; Kang, Meicun; Zhi, Rong; Zong, ZhangYang

doi:10.15376/biores.14.3.6837-6850

Cited by 7 publications

(4 citation statements)

References 23 publications

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“…The software of MDI Jade and Origin was used to process the XRD curve. The degree of crystallinity was calculated according to the following Equation (2-4): [23] CI(%) = I 002 − I AM I 002 (2)(3)(4) where CI represents the crystallinity index, I 002 is the intensity of the 002 crystalline peak, and I AM is the intensity of the amorphous halo.…”

Section: X-ray Diffraction (Xrd)mentioning

confidence: 99%

Preparation and Characterization of a Hard Capsule Based on Oxidized Rice Starch and Cellulose Nanocrystals

et al. 2021

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A hard capsule based on oxidized rice starch (ORS) and cellulose nanocrystals (CNC) is prepared by a dipping method and the glycerol and carrageenan are used as a plasticizer and gelling agent in the ORS/CNC gel solution, respectively. The viscosity of gel solution that is suitable for film-forming/capsule-forming is analyzed. When the content of CNC is 8.0%, the tensile strength of the ORS/CNC composite film is 10.09 MPa and increased by 196.0%. The loss on drying and the disintegration time of the ORS/CNC capsules are also investigated. The ORS/CNC capsules are analyzed by Fourier Transform Infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The results show that the ORS and CNC have good compatibility and good film-forming ability and can be used as excipients to prepare the hard capsules.

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Section: X-ray Diffraction (Xrd)mentioning

confidence: 99%

Preparation and Characterization of a Hard Capsule Based on Oxidized Rice Starch and Cellulose Nanocrystals

et al. 2021

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“…The end-of-life criteria applied to insulation paper is based on either a value of 200 for DP or retained tensile strength (20%) as the decisive factor to determine the material lifespan. However, the need of high performance electrical insulation materials (Prevost and Oommen 2006;Chen et al 2019;Jindal and Singh 2020;Xie et al 2020), as well as new industrial drying processes have produced new dielectric materials in which the determination of DP has been found problematic (Lukic et al 2021). Since the DP is a specific property of cellulose products (Marek and Szewczyk 2017), mechanical properties seem to be more suitable to quantify the insulation deterioration, working universally for almost all solid materials.…”

Section: Introductionmentioning

confidence: 99%

Fracture toughness as an alternative approach to quantify the ageing of insulation paper in oil

et al. 2021

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Oil-immersed transformers use paper and oil as insulation system which degrades slowly during the operation of these machines. Cellulose materials are used generally as insulation solid in power transformers. The degree of polymerization (DP), defined as number of repeating β-glucose residues in the cellulose molecule, is a critical property of cellulosic insulation material used in transformers, since it provides information about paper ageing and its mechanical strength. The fast-developing electric power industry demanding superior performance of electrical insulation materials has led to the development of new materials, as well as different drying techniques performed during transformer manufacturing and service when required. Both developments have caused some practical difficulties in the DP measurement. Moreover, the increasing interest in synthetic dielectric materials replacing cellulose materials requires measuring alternative properties to the DP to quantify the degradation of insulation solids over time. In this sense, this paper proposes the possibility of analyzing paper degradation through fracture toughness. This approach is different from the study of mechanical properties such as tensile strength or strain because it provides a tool for solving most practical problems in engineering mechanics, such as safety and life expectancy estimation of cracked structures and components which cannot to be considered through the traditional assessment of the mechanical resistance of the material. An accelerated thermal ageing of Kraft paper in mineral oil was carried out at 130 °C during different periods of time, to obtain information on the kinetics of the ageing degradation of the paper. Double-edged notched specimens were tested in tension to study their fracture toughness. The evolution of the load–displacement curves obtained for different ageing times at the ageing temperature of 130 °C was utilized to the determination of the stress intensity factor. Furthermore, different kinetic models based on this stress intensity factor were applied to relate its evolution over time as a function of the temperature. Finally, the correlation between the DP and stress intensity factor, which depends on the fiber angle, was also defined. Graphic abstract

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“…26,27 In the experimental investigation, the electrical breakdown strength of the cellulose−liquid composite is many times higher than that of single cellulose paper or liquid. 28,29 In the early years, several viewpoints have been proposed to explain this phenomenon theoretically. As for the insulation liquids, conductive bridges are easily formed by connecting impurities and ions after imposing an electric field; 30 in addition, the cellulose paper acted as a barrier to obstruct the conductive path formation, which makes the breakdown strength of the cellulose−liquid composite higher than the liquid.…”

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confidence: 99%

“…It is worth noting that the cavities between fibers of cellulose paper and decomposed molecules of liquids are taking more responsibility for its lower dielectric strength, respectively. , There are plenty of reports about improving the electrical insulation performance of insulating paper and liquids; however, the increased percentage of breakdown strength can only reach up to about 20%. , In the experimental investigation, the electrical breakdown strength of the cellulose–liquid composite is many times higher than that of single cellulose paper or liquid. , In the early years, several viewpoints have been proposed to explain this phenomenon theoretically. As for the insulation liquids, conductive bridges are easily formed by connecting impurities and ions after imposing an electric field; in addition, the cellulose paper acted as a barrier to obstruct the conductive path formation, which makes the breakdown strength of the cellulose–liquid composite higher than the liquid.…”

mentioning

confidence: 99%

Substantial Improvement of the Dielectric Strength of Cellulose–Liquid Composites: Effects of Traps at the Nanoscale Interface

Cui

Zhu

et al. 2020

J. Phys. Chem. Lett.

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The dielectric strength of cellulose−liquid composites is always about several times higher than that of the cellulose paper and insulating liquids. However, this experimental phenomenon has not yet been demonstrated theoretically. Herein, the spectra characterization, molecular simulation, and wave function analysis method provide a new insight that the role of nanoscale interfacial adsorption of cellulose−liquid is exclusive for composites affecting the charge separation and producing the deep-level traps to seriously hinder electromigration under an electric field, which is responsible for the difference in dielectric strength. Meanwhile, the π conjugation and σ−π hyperconjugation effects enhance the electrical stability of aromatic hydrocarbon insulating liquids. In conclusion, interfacial trap theory can be used to explain the correlation of dielectric strength between cellulose−liquid composites and cellulose paper or dielectric liquids. It can be expected that materials with high dielectric strength can be manufactured according to the fundamental study of interfacial trap theory.

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Effect of cellulose nanocrystals on the performance of oil-immersed transformer insulating paper

Cited by 7 publications

References 23 publications

Preparation and Characterization of a Hard Capsule Based on Oxidized Rice Starch and Cellulose Nanocrystals

Preparation and Characterization of a Hard Capsule Based on Oxidized Rice Starch and Cellulose Nanocrystals

Fracture toughness as an alternative approach to quantify the ageing of insulation paper in oil

Substantial Improvement of the Dielectric Strength of Cellulose–Liquid Composites: Effects of Traps at the Nanoscale Interface

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