Composites with Hydrophobic Surfaces

Abstract

Methods for depositing fluoropolymer coatings onto the surfaces of carbon-fiber materials were examined. The water repellants were fluoroplastics F-2M and F-4D, use of which could more than double the hydrophobicity of the fibrous materials. It was shown that the fluoroplastic coatings had high chemical resistance.The creation of hydrophobic and superhydrophobic surfaces is a critical issue in many areas of science and technology. The term hydrophobicity is understood to mean the water-repellent surface properties that can be estimated from the water contact angle. Coatings and materials with contact angles >90° are considered to be hydrophobic. Superhydrophobic surfaces with contact angles >150° are especially interesting. It is noteworthy that not only the surface chemical structure but also its relief (morphology) are responsible for the hydrophobic properties [1].Fibrous materials with highly hydrophobic coatings are used in various areas such as medicine, hydrogen energy, lipophilic absorbents, etc. [2][3][4]. Polyolefins, organosilicon materials, paraffins, etc. can be used as hydrophobic coatings. However, fluoropolymer coatings, which are also resistant to chemicals, heat, and frost and have low electrical conductivity, are the most hydrophobic.Polytetrafluoroethylene is the best water repellent. Common methods for depositing it on fibrous materials include powder spraying and coating from suspensions [5,6]. Fluoroplastics that are soluble in organic solvents can be deposited on fiber and material surfaces from solutions. An interesting method for depositing fluoroplastic coatings using tetrafluoroethylene telomers in acetone was reported [7].The goal of the present work was to compare the abilities of F-2M fluoroplastic in DMF and F-4D fluoroplastic in an aqueous suspension to produce a hydrophobic surface. Carbon-carbon composite sheets (CS Toray) (Japan), pilot batches of Russian sheets (PS RF), and a nonwoven composite produced in Russia (NC RF) were treated with water repellents.The hydrophobicity of samples before and after depositing the polymer coatings was estimated from the contact angle of a water drop on the surface (Fig. 1) [8].The coating was applied by soaking if solutions of fluoroplastic F-2M were used. The suspension of fluoroplastic F-4D was applied by spraying or dipping the samples. Figures 2 and 3 show functions characterizing the contact angle and its change after treating the materials with solutions and suspensions with various concentrations of F-2M and F-4D.The hydrophobicity of the material surfaces increased significantly after depositing the fluoroplastic coatings on them. Even treatment with 1% solutions and suspensions of the fluoroplastics increased significantly the hydrophobicity. Using water-repellent concentrations >2% led to no further significant increase of the hydrophobicity. The exception was carbon-fiber material NC RF, the hydrophobicity of which increased from 100° to 120° after treatment with 1% and 10% solutions, respectively, of F-2M in DMF (Fig. 2).A compar...

Influence of Accelerated Weathering on the Mechanical, Fracture Morphology, Thermal Stability, Contact Angle, and Water Absorption Properties of Natural Fiber Fabric-Based Epoxy Hybrid Composites

“…The superhydrophobic surface (contact angle greater than 150°) repels water and reduces the water absorption. Similarly, if the contact angle is less than 10°, the composite will be superhydrophilic with higher wettability and good self-cleaning ability [ 38 , 39 , 40 ]. For outdoor applications, the composite structures are usually coated with paint, and for coating hydrophilic surfaces are preferred.…”

EMI Shielding of the Hydrophobic, Flexible, Lightweight Carbonless Nano-Plate Composites

“…In addition, the water hating materials increase contact angle whereas water loving (polar materials) significantly improve hydrophilic nature. Furthermore, increasing the surface roughness, and groves, rise the surface energy, although, surface morphology, and chemical composition also affect the wettability of the surface [ 13 , 25 , 26 ]. The hydrophobic composite is an attractive candidate in the microelectronic device and material with other properties such as oxidation resistance, antifouling, self-cleaning, are highly preferable as these properties improve lifespan of the electronic devices [ 27 ].…”