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Effects of Substrate Composition and Roughness on Mechanical Properties and Conformality of Parylene C Coatings



Adrian E. Verwolf, Grady S. White, Chris M. Poling


Roughness and nanomechanical properties of poly(chloro-para-xylylene) coatings are shown to be affected by both chemical composition and surface roughness of four different metallic substrates. Nanoindentation was used to determine reduced elastic modulus (Er) and hardness (H) of 16-µm-thick coatings vapor-deposited on mill-finished samples of aluminum, copper, nickel steel, and stainless steel. Profilometry was used to directly compare average surface roughnesses (Sa) of the polymeric coatings to the roughnesses of the underlying metals, thereby providing a quantitative index for determining conformality. All Er and H distributions for the various metals were positively skewed, which precluded use of simple averages for purposes of comparison. However, careful analysis of the nanoindentation and profilometry data using robust, alternate techniques indicated that: 1) coatings were consistently smoother and flatter than their underlying substrates, i.e., they were not truly conformal, 2) the polymer’s surface topography on a given substrate biased Er and H results toward higher values than would have been observed for perfectly flat coatings, and 3) nanomechanical properties of poly(chloro-para-xylylene) were affected by the chemical composition of the substrates independently of the effects of substrate roughness.
Journal of Membrane Science


Parylene C, nanoindentation, hardness, reduced elastic modulus, conformal coating


Verwolf, A. , White, G. and Poling, C. (2012), Effects of Substrate Composition and Roughness on Mechanical Properties and Conformality of Parylene C Coatings, Journal of Membrane Science, [online], (Accessed April 22, 2024)
Created May 17, 2012, Updated November 10, 2018