Fractal phenomena. Dependence of hydrophobicity on surface appearance and structural features of SIR insulators

Wang, X.; Yoshimura, Noboru

doi:10.1109/94.822015

Cited by 17 publications

(6 citation statements)

References 11 publications

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“…The wetting mechanisms of liquid drops on solid substrates have been reported to be complicated by surface appearance and structural features such as self-similar patterns (fractal structure). − The wetting behaviors of fractal structures is different from those of ordinarily ordered structures (even with roughness). The rough surfaces of polymeric materials typically display the fractal property by aging or natural/man-made roughening procedures (i.e., sandpaper).…”

Section: Discussionmentioning

confidence: 99%

“…The rough surfaces of polymeric materials typically display the fractal property by aging or natural/man-made roughening procedures (i.e., sandpaper). By the characteristic behavior of fractal surfaces, the hydrophobicity of the appropriately roughened surfaces can be enhanced . On the other hand, an apparent contact angle of water drops on a flat surface (>60°) can suddenly decrease to zero on a fractal structure .…”

Section: Discussionmentioning

confidence: 99%

“…By the characteristic behavior of fractal surfaces, the hydrophobicity of the appropriately roughened surfaces can be enhanced. 48 On the other hand, an apparent contact angle of water drops on a flat surface (>60°) can suddenly decrease to zero on a fractal structure. 50 Liquid wetting on multifractal hierarchical singlewalled carbon nanotube films suggests a dynamic change in the hydrophilicity/hydrophobicity of materials.…”

Section: ■ Conclusionmentioning

confidence: 99%

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Nano/Micro Natural Patterns of Hydrogels against Water Loss

Ahn

Lee

2020

ACS Appl. Bio Mater.

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Water loss can be delayed by trapping it within a polymeric network, i.e. hydrogel. However, the dynamic response of natural materials has not been explained to maintain water levels relatively constant against varying environmental conditions. In this study, patterned polymeric materials formed on plant seeds are observed to provide effective water retention ability against repeated dehydration−rehydration procedures. The perpendicular line pattern (layer-by-layer stack) of the polymer films induces lateral line patterns (surface lines) by a typical wrinkling mechanism, which contributes to the characteristic water interaction. The anisotropic line patterns on the seed surface generate more hydrophilic properties over the isotropic patterns against drying-out. The matric potential (Ψ m ) of water through the line patterned gel matrix generally shows higher efficiency over isotropically patterned gels. Anisotropic lines (i.e., wrinkles) are one of the most abundant patterning procedures, thus they are a more advantageous function occurring in natural systems. This study sheds light on material design technologies to control water interaction in porous materials for various applications.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: ■ Conclusionmentioning

confidence: 99%

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Nano/Micro Natural Patterns of Hydrogels against Water Loss

Ahn

Lee

2020

ACS Appl. Bio Mater.

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“…In general, the HTV silicone rubber surface is a rough surface with fractal feature [24], quantitative analysis of the change of surface physical morphology is essential to understand degradation phenomenon of HTV silicone rubber. The wavelet transform [25, 26] is an ideal technique for investigating the surface physical morphology because it can provide an insight into the stochastic properties of a fractal surface [27]. Based on the multiresolution signal decomposition (MRSD) algorithm [28], the detailed information of a fractal surface at different analytical resolutions can be obtained.…”

Section: Introductionmentioning

confidence: 99%

Effects of liquids immersion and drying on the surface properties of HTV silicone rubber: characterisation by contact angle and surface physical morphology

Gao¹,

Liang

Bao

et al. 2019

High Voltage

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High-temperature vulcanised (HTV) silicone rubber composite insulator has been widely used in extra-high and ultrahigh transmission lines due to its excellent electrical and mechanical performance. In practice use, liquids may encounter the composite insulator intermittently and can lead to the degradation and deterioration of silicone rubber. In the present research, the effects of liquids immersion and subsequent drying on the surface properties of HTV silicone rubber were investigated by means of the contact angle measurement and surface physical morphology measurement which was further analysed in terms of the discrete wavelet transform method, multiresolution signal decomposition algorithm, and three-dimensional fractal dimension calculation. Based on the experimental results, the mechanism of the loss and recovery of the hydrophobicity of HTV silicone rubber surface during the liquids immersion and subsequent drying processes were further explained by taking into consideration the embedded water molecules (and/or hydrated ions) on the HTV silicone rubber surface and the synergy of the increase in roughness/fractal dimension and low molecular weight siloxanes diffusion. This study is helpful for better understanding of the change of surface properties of HTV silicone rubber caused by environmental and electrical stresses.

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“…These low molecular weight(LMW) silicones are easily movable due to their low intermolecular interaction. Furthermore, they are spontaneously migrated to the surface from the bulk by diffision because they have lower surface energy than the high molecular weight SIR polymers and the surface energy of air is lower than that of SIR [1][2][3][4][5][6][7][8]. Therefore, the surface of SIR shows good hydrophobicity and its dynamic recovery property.…”

Section: Introductionmentioning

confidence: 99%

Effects of hydroxy silicone fluids on insulation properties of silicone rubber

Kang

Park

Ahn

et al.

Proceedings of the 7th International Conference on Properties and Applications of Dielectric Materials (Cat. No.03CH37417)

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The hydroxy silicone(HS) fluids in silicone rubber(SIR) have been generally used as processing agent. The addition of HS fluids to SIR for insulator housing material is required to meet the good electrical performance and the good processability. In this study, SIR with HS fluids was evaluated to investigate how the kinds of them affect insulation properties. The contact angle of the virgin sample of 40-HS SIR was low and its recovery rate was also slow. The recovery rate of 50-HS SIR was the highest being decreased with the viscosity increase of HS fluids. The recovery rate of 1,040-HS SIR was a little slow at the initial stage. But the contact angle of that increased rapidly at the medium stage. The traclung resistances and the corona aging resistance of 70-13s SIR and 1,040-HS SIR were excellent. It is clear that resistances on discharges like corona, tracking, and arc #depends largely on heat resistance of silicone fluids.

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Fractal phenomena. Dependence of hydrophobicity on surface appearance and structural features of SIR insulators

Cited by 17 publications

References 11 publications

Nano/Micro Natural Patterns of Hydrogels against Water Loss

Nano/Micro Natural Patterns of Hydrogels against Water Loss

Effects of liquids immersion and drying on the surface properties of HTV silicone rubber: characterisation by contact angle and surface physical morphology

Effects of hydroxy silicone fluids on insulation properties of silicone rubber

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