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Title: Effect of substrate roughness on the apparent surface free energy of sputter deposited superhydrophobic polytetrafluoroethylene coatings: A comparison of experimental data with different theoretical models

Abstract

We have studied the effect of substrate roughness on the wettability and the apparent surface free energy (SFE) of sputter deposited polytetrafluoroethylene (PTFE) coatings deposited on untreated glass (average roughness, R{sub a}=2.0 nm), plasma etched glass (R{sub a}=7.4 nm), and sandblasted glass (R{sub a}=4500 nm) substrates. The wettability of the PTFE coatings deposited on substrates with varying roughnesses was evaluated by measuring the apparent contact angle (CA) using a series of probe liquids from nonpolar aprotic to polar protic. The wettability measurements indicate that an apparent water CA of 152 deg. with a sliding angle of 8 deg. was achieved for PTFE coatings deposited on a substrate with R{sub a}=4500 nm. The superhydrophobicity observed in these coatings is attributed to the presence of dual scale roughness, densely packed microstructure and the presence of CF{sub 3} groups. Unlike the bulk PTFE which is mainly dispersive, the sputter deposited PTFE coatings are expected to have some degree of polar component due to the plasma treatment. In order to calculate the dispersive SFE of PTFE coatings, we have used the Girifalco-Good-Fowkes (GGF) method and validated it with the Zisman model. Furthermore, the Owens-Wendt model has been used to calculate the dispersive and themore » polar components of the apparent SFE of the PTFE coatings. These results are further corroborated using the Fowkes method. Finally, an ''equation of state'' theory proposed by Neumann has been used to calculate the apparent SFE values of the PTFE coatings. The results indicate that the apparent SFE values of the PTFE coatings obtained from the Owens-Wendt and the Fowkes methods are comparable to those obtained from the Neumann's method. The analyses further demonstrate that the GGF and the Zisman methods underestimate the apparent SFE values of the sputter deposited PTFE coatings.« less

Authors:
; ;  [1]
  1. Surface Engineering Division, National Aerospace Laboratories, CSIR, Bangalore 560 017 (India)
Publication Date:
OSTI Identifier:
21476339
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 108; Journal Issue: 1; Other Information: DOI: 10.1063/1.3456165; (c) 2010 American Institute of Physics; Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COATINGS; COMPARATIVE EVALUATIONS; DEPOSITION; EQUATIONS OF STATE; ETCHING; GLASS; MICROSTRUCTURE; PLASMA; ROUGHNESS; SPUTTERING; SUBSTRATES; SURFACE ENERGY; SURFACES; TEFLON; WETTABILITY; ENERGY; EQUATIONS; EVALUATION; FLUORINATED ALIPHATIC HYDROCARBONS; FREE ENERGY; HALOGENATED ALIPHATIC HYDROCARBONS; MATERIALS; ORGANIC COMPOUNDS; ORGANIC FLUORINE COMPOUNDS; ORGANIC HALOGEN COMPOUNDS; ORGANIC POLYMERS; PETROCHEMICALS; PETROLEUM PRODUCTS; PHYSICAL PROPERTIES; PLASTICS; POLYETHYLENES; POLYMERS; POLYOLEFINS; POLYTETRAFLUOROETHYLENE; SURFACE FINISHING; SURFACE PROPERTIES; SYNTHETIC MATERIALS; THERMODYNAMIC PROPERTIES

Citation Formats

Selvakumar, N, Barshilia, Harish C, and Rajam, K S. Effect of substrate roughness on the apparent surface free energy of sputter deposited superhydrophobic polytetrafluoroethylene coatings: A comparison of experimental data with different theoretical models. United States: N. p., 2010. Web. doi:10.1063/1.3456165.
Selvakumar, N, Barshilia, Harish C, & Rajam, K S. Effect of substrate roughness on the apparent surface free energy of sputter deposited superhydrophobic polytetrafluoroethylene coatings: A comparison of experimental data with different theoretical models. United States. https://doi.org/10.1063/1.3456165
Selvakumar, N, Barshilia, Harish C, and Rajam, K S. 2010. "Effect of substrate roughness on the apparent surface free energy of sputter deposited superhydrophobic polytetrafluoroethylene coatings: A comparison of experimental data with different theoretical models". United States. https://doi.org/10.1063/1.3456165.
@article{osti_21476339,
title = {Effect of substrate roughness on the apparent surface free energy of sputter deposited superhydrophobic polytetrafluoroethylene coatings: A comparison of experimental data with different theoretical models},
author = {Selvakumar, N and Barshilia, Harish C and Rajam, K S},
abstractNote = {We have studied the effect of substrate roughness on the wettability and the apparent surface free energy (SFE) of sputter deposited polytetrafluoroethylene (PTFE) coatings deposited on untreated glass (average roughness, R{sub a}=2.0 nm), plasma etched glass (R{sub a}=7.4 nm), and sandblasted glass (R{sub a}=4500 nm) substrates. The wettability of the PTFE coatings deposited on substrates with varying roughnesses was evaluated by measuring the apparent contact angle (CA) using a series of probe liquids from nonpolar aprotic to polar protic. The wettability measurements indicate that an apparent water CA of 152 deg. with a sliding angle of 8 deg. was achieved for PTFE coatings deposited on a substrate with R{sub a}=4500 nm. The superhydrophobicity observed in these coatings is attributed to the presence of dual scale roughness, densely packed microstructure and the presence of CF{sub 3} groups. Unlike the bulk PTFE which is mainly dispersive, the sputter deposited PTFE coatings are expected to have some degree of polar component due to the plasma treatment. In order to calculate the dispersive SFE of PTFE coatings, we have used the Girifalco-Good-Fowkes (GGF) method and validated it with the Zisman model. Furthermore, the Owens-Wendt model has been used to calculate the dispersive and the polar components of the apparent SFE of the PTFE coatings. These results are further corroborated using the Fowkes method. Finally, an ''equation of state'' theory proposed by Neumann has been used to calculate the apparent SFE values of the PTFE coatings. The results indicate that the apparent SFE values of the PTFE coatings obtained from the Owens-Wendt and the Fowkes methods are comparable to those obtained from the Neumann's method. The analyses further demonstrate that the GGF and the Zisman methods underestimate the apparent SFE values of the sputter deposited PTFE coatings.},
doi = {10.1063/1.3456165},
url = {https://www.osti.gov/biblio/21476339}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 1,
volume = 108,
place = {United States},
year = {Thu Jul 15 00:00:00 EDT 2010},
month = {Thu Jul 15 00:00:00 EDT 2010}
}