Interfacial work

JKR type mea.surement.s on monolayers depo.sited on. soft elastomers. The recent interest in the JKR experiments has been stimulated by the work of Chaudhury and coworkers [47-50J. In a 1991 paper, Chaudhury and White-sides [47] reported their extensive studies on the measurement of interfacial work of adhesion and surface energies of elastomeric solids. The motivation for this work was to study the physico-organic chemistry of solid surfaces and interfaces. 

Sometimes the failure occurs by propagation of a crack that starts at the top and travels downward until the interface is completely debonded. In this case, the fracture mechanics analysis using the energy balance approach has been applied [92] in which P, relates to specimen dimensions, elastic constants of fiber and matrix, initial crack length, and interfacial work of fracture (W,). 

Fig. 11. Dependence of the peel strength of tin plate/epoxy systems on coating thickness for coatings cast from DTPM and methyl cello-solve. These theoretical curves were constructed using experimental values for modulus, critical coating thickness, solvent evaporation rate, solution concentration and interfacial work of adhesion96 (Reprinted from Ref. 96, p. 123 by cautesy of Plenum Press)...

Here, 7pias is a proportionality factor in front of <7/1. It describes the interfacial work in the case of pure plastic, reversible work. If the actual proportionality factor 7 is different, then the last term becomes effective. 

This is a central equation in the theoretical evaluation of interfacial tensions when the grand canonical partition function can be obtained from some model, / can immediately be found by differentiation with respect to A. Because V is kept constant, only interfacial work is considered. 

The interfacial work by viscous and pressure forces yields ... 

The interfacial work by viscous and pressure forces (3.168) can be rearranged decomposing the velocity as ... 

Croll illustrated that interfacial work of adhesion could be found by peeling test. 

If the coating is peeled at a constant rate, the rate of change of total internal energy of coating is equal to zero. Thus the peeling strength is related to the interfacial work of adhesion as follows (Figure 7.3.28),... 

Interfacial work of adhesion, y, can be measured by spontaneous peeling test using above equation. Spontaneous peeling thickness, tp, can be directly measured, and the recoverable strain energy, Ur, for an elastic material under a one-dimensional strain is. 

Interfacial work of adhesion Aetivity coefficient Heat of vaporization [J/kg]... 

Note that the symbol d is used for the differential of a state function or state variable whereas 5 just indicates an infinitesimally small amount of a quantity that is dependent on the path taken). For w and, hence, Sw, various types of work may be considered, such as mechanical work resulting from compression or expansion of the system, electrical work, interfacial work associated with expanding or reducing the interfacial area between two phases, and chemical work due to the exchange of matter between the system and environment. All types of work are expressed as dT, where X and Y are state variables. X is an intensive property (independent of the... 

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