The Effect of Surface Contamination on Adhesive Forces as Measured by Contact Mechanics

Abstract

The contact adhesive forces between two surfaces, one being a soft hemisphere and the other being a hard plate, can readily be determined by applying an external compressive load to mate the two surfaces and subsequently applying a tensile load to peel the surfaces apart. The contact region is assumed the superposition of elastic Hertzian pressure and of the attractive surface forces that act onIy over the contact area. What are the effects of the degree of surface contamination on adhesive forces? Clean aluminum surfaces were coated with hexadecane as a controlled contaminant. The force required to pull an elastomeric hemisphere from a surface was determined by contact mechanics, via the JKR model, using a model siloxane network for the elastomeric contact sphere. Due to the dispersive nature of the elastomer surface, larger forces were required to pull the sphere from a contaminated surface than a clean aluminum oxide surface.

Adhesion enhancement of polymer blend interfaces by reactive block copolymer brushes

“…When the silanol end groups were replaced by reaction with hexamethyldisilazane (which replaces the end-group with a trimethylsilyl group), the hysteresis was reduced by up to 80%. In contrast, Emerson et al [30] demonstrated that the presence of SiH groups was not required for hysteresis to occur between toluene-extracted hemispheres. Unreacted SiH groups were removed by reaction with ethylene gas, but hysteresis was still observed.…”

Studies on the disbonding initiation of interfacial cracks.

“…This higher adhesion is expected, given that polyimide typically exhibits a lower surface energy than the native oxide on the surface of aluminum. A total solid surface energy of approximately 40 mJ/m 2 has been measured for polyimide [70], while aluminum oxide has range of values reported throughout the literature, ranging anywhere from 40 to 638 mJ/m 2 , depending on the surface preparation [71,72]. Luo and Wong report that the dispersive surface energy of UV/ozone-cleaned alumina is 45.9 mJ/m 2 [73].…”