EFFECTS OF THIN, SEMIRIGID COATINGS ON THE ADHESION-INDUCED DEFORMATIONS BETWEEN RIGID PARTICLES AND SOFT SUBSTRATES

Glass particles, having nominal radii of approximately 20 mum, were deposited onto polyurethane substrates, which had been overcoated with a 5-mum-thick thermoplastic layer, and the surface-force-induced contact radii were measured using scanning electron microscopy. It was found that the size of the deformations depends only on the modulus of the coating and not on the modulus of the underlying substrate. The measured contact radii were found to scale with the Young's modulus of the substrate for the uncoated polyurethane substrates according to the predictions of the JKR model [K. L. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Soc. London Ser. A 324, 301 (1971)]. However, the contact radii on the overcoated substrates appear to be more accurately predicted by the DMT theory [B. V. Derjaguin, V. M. Muller, and Yu P. Toporov, J. Colloid Interface Sci. 53, 314 (1975)].