Applicability of Cassie-Baxter equation for superhydrophobic fluoropolymer silica composite films


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CENGİZ U., Cansoy C. E.

APPLIED SURFACE SCIENCE, vol.335, pp.99-106, 2015 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 335
  • Publication Date: 2015
  • Doi Number: 10.1016/j.apsusc.2015.02.033
  • Journal Name: APPLIED SURFACE SCIENCE
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.99-106
  • Keywords: Superhydrophobicity, Oleophobicity, Cassie-Baxter equation, Contact angle hysteresis, Work of adhesion, CONTACT-ANGLE HYSTERESIS, SURFACE-ROUGHNESS, LENGTH SCALES, ADHESION, WATER, WORK, DROPLETS, SMOOTH, HYDROPHOBICITY, TRANSPARENT

Abstract

In this study, surface topographies and wettabilities of flat and composite rough films of perfluoro-styrene (TM/S) random copolymers with silica particles were investigated. The water and oil repellencies of flat TM/S copolymer and rough silica-TM/S composite surfaces were studied with varying perfluoro and silica contents. Increase in silica content resulted in an increase in water contact angle values; water contact angle values increased from 113 up to 170, and the resultant surfaces were showing extremely superhydrophobic behavior depending on their silica contents. However a decrease in hexadecane contact angles from 61 to 25 depending on both silica %wt and perfluoro content of the TM/S copolymer was seen. Applicability of Cassie-Baxter equation was also investigated for TM/S copolymer films with silica particles. The results showed that Cassie-Baxter equation cannot be used for superhydrophobic surfaces, however, can be applied to oleophilic surfaces with caution. The oil repellencies of TM/S flat films in the terms of contact angle hysteresis was also compared with perfluoroethyl alkyl methacrylate-methyl methacrylate copolymer (TM/MMA) by using oil drops with varying surface tensions between 20.9 mN/m and 26.9 mN/m. The surface oleophobicities were changed according to the characteristics of the functional groups of MMA and S. The dependency of work of adhesion results of TM/S flat surfaces on wt.% of perfluoroalkyl content was also examined. (C) 2015 Elsevier B.V. All rights reserved.