Hydrophobic thiol-ene surfaces fabricated via plasma activation and photo polymerization

• Published in: Journal of physics. Conference series Vol. 901; no. 1; pp. 12164 - 12170
• Main Authors: Champathet, P, Ervithayasuporn, V, Osotchan, T, Dangtip, S
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.09.2017
• Subjects: Alumina; Aluminum oxide; Coating; Contact angle; Dielectric barrier discharge; Electric contacts; Functional groups; Hydrophobicity; Photoinitiators; Photopolymerization; Physics; Polymerization; Polymers; Sheets; Siloxanes; Substrates; Surface roughness
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/901/1/012164

Alumina, such as glazed alumina for electrical insulator, operated in an open field subjects to a very harsh condition; resulting in lifetime shortening. Coating hydrophobic layer on alumina surface can help prolonging its lifetime. In this study, 25 ×25 mm alumina sheets were used as substrates. The hydrophobic composite polymers were prepared from (3-mercaptopropyl)trimethoxysilane(MPTMS), 2,4,6,8-tetramethyl-2,4,6,8tetravinylcyclotetra siloxane(TMTVSi), pentaerythritoltetra(3-mercaptopropionate)(PETMP), 2,2-dimethoxy-2-phe nylaceto phenone(photoinitiator) and heptadecafluorodecylmethacrylate(HEFDMA) via the thiol-ene reaction. The alumina sheets were first activated by dielectric-barrier discharge plasma to improve its adhesion. All the polymers were found to optimize at the ratio of (MPTMS:TMTVSi:PETMP:HDFDMA) to 4:2:1:2 for coating on the alumina substrate. To enhance polymerization, 2,2-dimethoxy-2-phenylaceto phenome was also used as a photoinitiator A proper mixing sequence in the thiol-ene reaction results in film with excellent surface retention after prolong soaking in solvent such as acetone. FTIR shows that S-H and C=C functional groups have significantly changed after photopolymerization and thermally cured. The static contact angle increase from mere 53.0°±1.5° of the uncoated substrate to 120.0°±1.2° after coating. SEM shows the film with clear appearance of a few-micron thick. Under AFM, the coated surface roughness was about 9.3 nm with evenly distributed spikes of a few nanometer in height. The cross-cut test also confirmed the film was very smooth and none of the square of the films detached.