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Adhesive thermodynamic value

Here, Si, S2, S3 are the interfaces of solid-liquid 1, solid—liquid 2, and liquid 1-liquid 2, and v is the rate of separation. When cementing in water and oil products, the adhesive is liquid 1 and the medium is liquid 2. Equation (5.2) indicates that spontaneous wetting (without mechanical work to the interface) is possible when the surface tensions of the adhesive and the liquid are equal, i.e., for crad Hq = although the maximal value of (Tadliq is desirable because it is directly proportional to the adhesion thermodynamic work. [Pg.266]

We have seen how the adhesion of coatings and films varies remarkably with the elasticity, geometry and loading condition of the test method. However, it is also essential to understand how the delaminating crack can be inhibited by various mechanisms which amplify the adhesion to give adhesion energies up to 100,000 J m 2, far higher than the thermodynamic values of 0. t-10 J m 2 known to apply to smooth reversible interfaces. [Pg.347]

Treated side Untreated side Thermodynamic work of adhesion, calculated value (mN m ) Peel strength (N)... [Pg.192]

In a liquid medium, for which there is a liquid interlayer between the contiguous bodies, and the effects of capillary, electric, and Coulomb forces are excluded (see 11-13), adhesion is due solely to the molecular forces fthe disjoining pressure opposes adhesion). The value of the molecular forces is directly proportional to the dimensions of the particles [see Eqs. (1 47) and (1.49)]. For an aqueous medium the experimental results relating to the dependence of the adhesive forces on particle dimensions coincide with the theoretical data, and Deryagin s thermodynamic theory of adhesion is practically confirmed (see 5). [Pg.156]

The premise of the above analysis is the fact that it has treated the interfacial and bulk viscoelasticity equally (linearly viscoelastic experiencing similar time scales of relaxation). Falsafi et al. make an assumption that the adhesion energy G is constant in the course of loading experiments and its value corresponds to the thermodynamic work of adhesion W. By incorporating the time-dependent part of K t) into the left-hand side (LHS) of Eq. 61 and convoluting it with the evolution of the cube of the contact radius in the entire course of the contact, one can generate a set of [LHS(t), P(0J data. By applying the same procedure described for the elastic case, now the set of [LHS(t), / (Ol points can be fitted to the Eq. 61 for the best values of A"(I) and W. [Pg.127]

These comments should not be interpreted to mean that measures of wettability are useless at predicting adhesion. They do seem clearly to indicate that contact angles and critical surface tensions reported for wood are not necessarily thermodynamic quantities or well-defined material parameters. Because most contact angles are dynamic values, they should be interpreted with caution and considered as relative measures of adhesion, for which the absolute scale is yet unknown. Further, we need to keep in mind that although wetting is necessary for adhesion, it may not be the limiting factor in many real situations. [Pg.166]

Possibility for the preparation of multi-component alloys with concentrations of elements much higher than their equilibrium values. This is due to the fact that the film composition is mainly determined by the relative contents of components in the stream of sputtered atoms and by the adhesion factor, but is not defined by thermodynamic equilibrium. [Pg.587]

Consider a non-reactive system consisting of a binary liquid alloy A-B and an oxide substrate such as AI1O3 at constant temperature. A simple statistical thermodynamic model has been developed (Li et al. 1989) to predict the contact angle and the work of adhesion isotherms, 0(XB) and Wa(XB), from the known values of contact angles... [Pg.239]

In principle, an equality between the thermodynamic work of adhesion of liquid-solid systems and the work needed to separate an interface might be expected for simple systems and this has been observed for failure of adhesive-polymer interfaces bonded by van der Waals forces, (Kinloch 1987). Similarly, empirical correlations of interfacial strengths and work of adhesion values of solidified interfaces have been reported for some nominally non-reactive pure metal/ceramic systems. However, mechanical separation of such interfaces is a complex process that usually involves plastic deformation of the lattices, and hence their works of fracture are often at least ten and sometimes one hundred times larger than the works of adhesion, (Howe 1993). Nevertheless, for non-reactive metal/ceramic couples, it is now widely recognised that the energy dissipated by plasticity (and as a result the fracture energy of the interface) scales with the thermodynamic work of adhesion (Reimanis et al. 1991, Howe 1993, Tomsiaet al. 1995). [Pg.373]

According to the laws of thermodynamics, the difference of surface tension between adherend and adhesive is decisive for the wettability of the system. The surface tension values are given in mN/m (milli Newton per meter) in the following order of magnitude ... [Pg.61]

Equation (645) shows that contact angle is a thermodynamic quantity, which can be related to the work of adhesion and interfacial free energy terms. When 6 values are small, the work of adhesion is high and considerable energy must be spent to separate the solid from the liquid. If 0 = 0°, then W L = 2yv if 0 = 90°, then W L = yLV, and if 0 = 180°, then W1L = 0, which means that no work needs to be done to separate a completely spherical mercury drop from a solid surface (or a water drop from a superhydrophobic polymer surface), and indeed these drops roll down very easily even with a 1° inclination angle of the flat substrate. [Pg.310]

Thermodynamic evidence for preferential displacement of the adhesive from the interface by water is provided by the work of Gledhill and Kinloch (1). By approximating the value of the work of adhesion between an epoxy adhesive and iron oxide surface, they were able to show that in the absence of water this value was positive and stable. If, however, water is present at the interface the work of adhesion shifts to a negative, and hence unstable value. It follows that under moist conditions, the locus of failure will likely be at the interface, resulting in a lower strength. This is what one observes experimentally. [Pg.120]

Effectively, when viscoelastic losses are negligible (i.e., when performing experiments at very low peel rate or high temperature), 4>-> 1 and G must tend toward IV. However, the resulting threshold value Gq is generally 100 to 1000 times higher than the thermodynamic work of adhesion, IV. [Pg.68]


See other pages where Adhesive thermodynamic value is mentioned: [Pg.43]    [Pg.332]    [Pg.600]    [Pg.108]    [Pg.139]    [Pg.5]    [Pg.9]    [Pg.102]    [Pg.121]    [Pg.205]    [Pg.210]    [Pg.202]    [Pg.45]    [Pg.1481]    [Pg.141]    [Pg.107]    [Pg.118]    [Pg.254]    [Pg.214]    [Pg.323]    [Pg.374]    [Pg.68]    [Pg.336]    [Pg.347]    [Pg.179]    [Pg.111]    [Pg.357]    [Pg.555]    [Pg.46]    [Pg.48]    [Pg.227]    [Pg.26]    [Pg.189]    [Pg.356]    [Pg.143]    [Pg.9]   
See also in sourсe #XX -- [ Pg.41 ]




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Thermodynamic adhesion

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