Adhesive Force by Detachment of Individual Particles

Determination of Adhesive Forces by Detachment of Individual Particles 

In experiments involving a determination of the interaction force of macroparticles, the test specimens may be two spherical particles with diameters of the order of a few millimeters, one such spherical particle and a plane surface, or the fused ends of fibers (Fig. III.9) made of glass, quartz, or a metal. The ends may be either rounded (a), spherical (b), or flat (c). 

The angle ol is either measured directly or is calculated from the deviation of the fiber with the fused end from its original position, as measured by means of a micrometer (Fig. III.l 1). This method is quite accurate since the error of measurement is determined entirely by the accuracy with which the angle ot is measured. 

In apparatus of the second type, the adhesive forces are evaluated by reference to the elongation of a quartz spring at the instant of particle detachment, i.e.. 

Corn [89] used a microbalance with a balance arm. With this particular apparatus, the quantity Ah corresponds to the deflection of the arm this arm carries a fiber of the material under investigation with a sphere at the end (Fig. III.l2). With this apparatus, adhesive forces can be measured over a wide range, from 10 to 10 dyn. The relative error of measurement is no greater than 4-10% for particles with diameters of 21-31 /xm, the error increasing to 24% when the particle size is increased to 90 jLtm. 

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