Evaluating the Magnitude of Adhesion Adhesive Force

Evaluation of Adhesive Interaction by Means of Force. The dependence of adhesion number on the forces holding the particles of a monodisperse dust on a surface is commonly characterized by integral curves of adhesive force [14] (Fig. 1.2). The force of adhesion can be expressed in integral curves either in absolute quantities or in -units.f The force of adhesion ing -units, i.e., the ratio of adhesive force to the particle weight, has been termed the coefficient of adherence by G. I. Fuks [12]. 

The f6rce of adhesion is numerically equal to but opposite in direction to the force causing detachment of the adherent particles. The detachment force can be expressed indirectly, for example, in the form of centrifuge rpm, fre- 

Adhesion can be compared under different conditions either on the basis of the force required for detachment (or retention), of a given number of particles, or of the adhesion number (i.e., the number of remaining particles) for a given detachment force [18]. 

Fi is considerably smaller than the force F4 i.e., in the first case (curve 1), the majority of the particles are torn off more readily than in the fourth case (curve 4). Here, evidently, adhesion is better evaluated on the basis of the detachment force for an adhesion number of 50% (see Fig. 1.2.a). We must also note that certain cases are likewise possible, although less probable, in which the detachment force F50 will be equal for a family of curves (Fig. I.2.b) but will not reflect the features of adhesive interaction. 

Thus we see that the evaluation of adhesion on the basis of the detachment force at identical adhesion numbers (i.e., on the basis of F, in, F ax or so) can lead to errors. In exactly the same manner, the evaluation of adhesion on the basis of adhesion numbers at equal detachment forces can serve only as a relative characterization of the interaction forces between particles and surface. 

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