Surface study of perfluoropolyether-urethane cross-linked polymers

A surface study of two different monocomponent polyurethane coatings contai ning perfluoropolyether macromers is presented. Different techniques were u sed in order to investigate the structural characteristics of the two polym ers. In particular, transmission infrared spectroscopy provided information about the chemical groups and linkages present in the polymer network, and attenuated total reflectance spectra showed a higher concentration of urea groups close to the surface. X-ray photoelectron spectroscopy analysis at two different sampling depths showed clear evidence of fluorine enrichment and nitrogen depletion in the first nanometres of material with respect to the bulk composition of the two polymers. Analysis of the outermost layer b y time-of-flight secondary ion mass spectrometry confirmed the XPS data wit h a predominant presence of fluorinated fragments. Contact angles of the tw o coatings with water and paraffins were measured and the critical surface tension of wetting, gamma (c), was estimated (13-16 mN m(-1) at 20 degreesC ) and compared with the known data of other fluoropolymers, Copyright (C) 2 000 John Wiley & Sons, Ltd.