Influence of the magnetic force on the van der Waals force of superparamagnetic composite particles

• Adhesion force measurements with modified centrifugal method.
• Adhesion force measurements of magnetic particles within different magnetic fields.
• Magnetic force increases the v.d.W. force due to deformation within the contact zone.

Adhesion forces of superparamagnetic polystyrene-magnetite particles and polyvinylchloride, cellulose fiber felt, and stainless steel were measured. Three different surface roughnesses of the polyvinylchloride were tested. Experiments were carried out with a modified centrifugal method, which allowed the application of different magnetic field strengths during the experiment. It was shown that the total adhesion force is higher than the summation of the single forces. Deformation calculations show that the percentage increase of the contact area due to the magnetic force is similar to the increase of the van der Waals force in the stressed case. In the extreme case of a high magnetic force and a high surface roughness, the van der Waals force rose to ninety times its initial value.

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