Electrical Phenomena in Adhesion. I. Electron Atmospheres in Dielectrics

Abstract

Rapid breaks of metal-polymer-metal adhesive specimens have shown the presence of a charge density on the metallic surface, provided the break occurs at the metal-polymer interface, and a much smaller charge if it occurs in the interior of the polymer. This is analyzed in terms of the electron atmosphere existing external to the metal in a dielectric region of low barrier. The barrier values in certain cases are otherwise known to be of appropriate order of magnitude. Measured experimental surface charge densities permit estimation of the maximum limit of barrier height. Because of the presence of the charge distribution in the polymer, there is an electrostatic force on the adherend metal directed toward the dielectric polymer, which represents a contribution to the total adhesive forces opposing break. Such electrostatic contributions to adhesion have not previously been considered; their order of magnitude and their relation to the thickness of the adhesive are discussed. The qualitative agreement between the theory and a number of previously unexplained experimental results in the literature is shown.

Platinum metallization on silicon and silicates

“…These stresses are capable of fracturing even relatively strong coating-to-substrate bonds. General discussions of adhesion concern a wide technical scope [7,81,187], including how van der Waals interactions ( ∼ 0.1 eV) and chemical bonding (up to 10 eV) between adsorbing atoms and the substrate combine with atomistic diffusion processes that occur during the film's growth [188], the thermodynamics and kinetics of film agglomeration [189], residual and thermal stresses acquired during deposition and thermal cycling [67], electrostatic interactions arising due to the exchange of charge across the interface [81,190], corrosion chemistry [191,192], and fracture mechanics [193,194,195,196]. There is a gulf between this formidable combination of subjects and practical techniques like scotch tape and scratch testing that are used to directly assess whether a film can withstand the conditions defined by its intended application [7].…”

Friction in Magnetic Tapes I: Assessment of Relevant Theory

“…Deryagin (20) and Skinner et al (21) argue that when a polymer (insulator) is brought into contact with a metal, there will be a far larger separation of charges at the interface, which will produce an electrostatic attraction in addition to the Van der Waals attraction. Deryagin claims that practically the whole of the adhesion is electrostatic in origin.…”

Adhesion

“…This produces an electrostatic attraction in addition to the van der Waals interaction between the bodies (Johnsen and Rahbek, 1923;Skinner et al, 1953;Davies, 1973;Wahlin and Backstrom, 1974;. When the separation equals the atomic spacing, the bond resembles that within the bulk of the material.…”