Hydrophobic coating of expanded perlite particles by plasma polymerization

In this study, an RF plasma discharge was employed to deposit thin poly(hexafluorobutyl acrylate) (PHFBA) polymeric films on expanded perlite. A rotating plasma reactor was used to provide effective agitation and mixing of the particles during the depositions. Surface of expanded perlite, a hydrophilic porous material, was successfully transformed into super-hydrophobic due to the highly fluorinated chain of PHFBA. Deposition rates up to 42 nm/min were observed. The influences of plasma discharge conditions on wettability and water holding capacity of expanded perlite powders were investigated. Chemical and morphological properties of uncoated and coated expanded perlites were determined by SEM (EDS), FTIR, and contact angle measurements analyses. It is observed that the pulsed plasma approach helps to minimize undesirable monomer fragmentation while providing better film structure. It also should be emphasized that PECVD experiments did not change the morphology of the expanded perlite powders. The water holding capacity of expanded perlite was decreased from 70% down to around 4% upon coating on pulsing mode. (C) 2015 Elsevier B.V. All rights reserved.