Adhesion-induced deformations of polymeric substrates: Particle size dependence of the contact area

Adhesion-induced deformations of a polyurethane substrate in contact with cross-linked polystyrene spheres, having diameters ranging from less than 2 μm to approximately 12.5 μm were observed using scanning electron microscopy. The diameters of the contact areas were measured from the micrographs. It was found that the contact radius varied as the particle radius raised to the 0.75±0.05 power. Experimental results are compared to the predictions of various adhesion models. The results are also discussed in terms of the Dupré work of adhesion.