Effect of Chemical Functionality on Adhesion Hysteresis

Abstract

Studies of adhesion and adhesion hysteresis were carried out using cross-linked poly(dimethyl siloxane) (PDMS) semispherical surfaces and self-assembled model surfaces containing different chemical functionalities, using the JKR method, the contact mechanics of solids spreading their interfacial area under load. Hysteresis resulting from fast relaxation processes in the PDMS elastomer network was practically eliminated using stepwise loading and unloading protocols. The interfacial H-bonding between PDMS and both Si−OH and −COOH surfaces was shown to be an important chemical interaction causing significant adhesion hysteresis. The number of H-bonds between PDMS and Si−OH surfaces increased with contact time under compressive load, indicating pressure-induced reorganization of the PDMS network near the interface that increased the number of H-bonds. The interaction between PDMS and functionalized biphenylthiolate monolayers exhibited a smaller hysteresis, which is believed to be caused by dipolar interaction, whereas that between PDMS and nonpolar perfluorocarbon groups showed negligible hysteresis. The distinction in the behavior of the unloading data between H-bonding related interaction and dipolar interaction seems to indicate the difference in the nature between nonspecific (van der Waals, dipolar) and specific (donor−acceptor, H-bond, acid−base) interactions.

Formation of multilayers on silica surfaces of a cationic polyelectrolyte and dissolved and colloidal substances originating from mechanical wood pulp-Adsorption and influence on adhesion

“…In the former case, the curves showed little hysteresis, as expected, and the work of adhesion obtained by fitting the data to the JKR-theory was W A = 41.5 mJ/m 2 which is in good agreement with the literature [30]. The corresponding curves for PDMS against silica showed a very large hysteresis, which is in full agreement with the results reported by Kim et al [42]. The loading data gave a value of W A = 53 mJ/m 2 .…”

Use of Self-assembled Monolayers at Variable Coverage to Control Interface Bonding in a Model Study of Interfacial Fracture: Pure Shear Loading

“….Much effort in adhesion science has been devoted toward understanding the relationship between fundamental interracial interactions and engineering fracture quantities such as joint strength or fracture energy [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These relationships are important from the standpoint of designing interracial chemistry sufficient to provide the level of mechanical strength required for a particular application.…”

“…Here, the fracture energy has been shown to be separable into a product of the intrinsic interface energy and a dissipation function which depends upon rate and temperature. [8][9][10] If the elastomer interacts with the substrate through only van der Waals interactions, the intrinsic interface energy approaches W. at low rates. However, if the elastomer is covalently bonded to the substrate, the interactions are not reversible and the intrinsic interface energy is not related to W.. For either case, the viscoelastic material response which determines the amount of energy dissipated is governed by monomeric friction and described by timetemperature superposition using the WLF equation.…”

Combinatorial Approach to Characterizing Epoxy Curing

“…These chains would provide a source of dissipation that requires additional energy to drive crack propagation. [28][29][30][31][32] The monotonic decrease in WOD above 85 8C may be a result of the further conversion of epoxy groups to ether groups at the surface [33,34] but further analysis is required to confirm this hypothesis.…”