Combined XPS and contact angle studies of flat and rough ethylene‐vinyl acetate copolymer films

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Abstract
Flat and rough thin films were prepared by dip coating using LDPE, PVAc, and EVA polymers containing 12–40% VA contents. Surface free energy of flat films was determined by measuring contact angles. Surface atomic composition was investigated by XPS at 0° and 60° take‐off angles. XPS results show that hydrophobic PE component was found to enrich at the near‐surface region for all EVA samples for a depth of ∼ 5 nm for both flat and rough surfaces, whereas hydrophilic VA component was enriched on the surface when VA < 18% for only at 10 nm depth. The difference between the XPS results of the flat and rough surfaces was not significant for EVA samples except EVA‐33 surface where the atomic oxygen content decreased 15–20% for rough surfaces. Contact angle hysteresis values for the rough samples were much larger than that of the flat samples for LDPE and EVA‐12 surfaces due to the presence of partial trapping of air pockets on these rough surfaces. A good agreement was obtained between surface concentration of atomic oxygen in the 5 nm outermost layer and γ surface free energy component especially for the samples having high VA contents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

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