ON THE INFLUENCE OF MOLECULAR FORCES ON THE DEFORMATION OF AN ELASTICSPHERE AND ITS STICKING TO A RIGID PLANE

In this paper we have examined what influence the molecular interactio n of spherical elastic particles with the rigid substrate exerts on th eir adhesion, the form close to the contact zone, and the dimensions o f that zone. By having recourse to the computer numerical solution of the equations of the theory of elasticity (the interaction with the su bstrate was modeled by the Lennard-Jones potential), the distribution of pressures within the contact zone and around it, the profile of a p article in the vicinity of the contact, and the contact and noncontact components of the force of interaction of the particle with the subst rate at different approaches of the particle to the plane have been as certained. The dependence of the particle tearing-off force on the sin gle dimensionless parameter mu = (32/3pi) x [2phi2R(1 - eta2)2/piE2eps ilon3]1/3 was established, this parameter comprising the radius of the particle, R, its clastic constants, E and eta, and the characteristic s of the potential of interaction with the substrate, phi and epsilon. The applicability limits have been determined of each of the two exis ting theories describing the tearing off of an elastic particle from t he substrate, i.e., the theories of Derjaguin et al. and Johnson et al . It is proved that at mu < 1 the sticking force is completely determi ned by Derjaguin's formula and at mu much greater than 1 the differenc e from this formula consists in the appearance of a factor, 3/4. It is demonstrated that for the most part of dispersions of colloidal grade of dispersity the applicability of Derjaguin's formula is quite justi fied and does not require any revision.