Adhesion parameter

Barton AFM (1983). Handbook of Solubility Parameters and Other Adhesion Parameters, CRC-Press, Boca Raton, FL. 

Applications. The following uses of contact angle were reported in the literature surface energy of different sizes for fibers, correlation between contact angle of fiber and interlaminar shear strength of composite, effect of surface treatment of fillers for paints, the matrix-filler adhesion parameter for PS filled with CaCO, dispersion stability of PEO-modified kaolin particles, determination of contact angle of carbon fibers and its dependence on treatment, wettability of fiber sur-... 

F is some sort of adhesion parameter, i.e. the greater F the higher the tenacity of the crystals to stick together on the surface with a lower removal rate F is the shear force... 

In future studies, we propose to add to the contact angle measurements (which probe only 5-10 A of the layer) XPS and FTIR spectroscopy analysis, in order to understand the kinetics of the reaction in the interior of the pulsed plasma polymer thin film. Once quantitative elucidation of the reactivity of the pulsed plasma polymer thin film has been fuUy accomplished, adhesion strength measurements will be performed and correlations between adhesion parameters and thermodynamic parameters wiU be explored. This wiU be the subject of a further paper. 

Figure 12.5 Dependence of the adhesion parameter A on normalised number of non-screened points on the filler surface, N /

Figure 12.7 Dependence of the strength, (c ), of an interfacial layer on adhesion parameter A for PHE-Gr-I (1, 3) and PHE-Gr-II (2, 3). 1, 2 calculated from Equation 12.13, 3 from Leidner-Woodham equation at K= 2 [22].

Figure 12.10 Dependence of the critical structural defect length (a t) and adhesion parameter (A) for 1 PHE-Gr-I (1) and 2 PHE-Gr-II...

Using this concept. Hammer and Lauffenburger [1987] studied the effect of external flow on cell adhesion. The cell is modeled as a solid sphere, and the receptors at the surface of the sphere are assumed to diffuse and to convect into the contact area. The main finding is that the adhesion parameters, such as the reverse and forward reaction rates and the receptor number, have a strong influence on the peeling of the cell from the substrate. 

In order to take into account the cell deformability, which has shown to be necessary for calculating the magnitude of the adhesion force, Dong and Lei [2000] have modeled the cell as a liquid drop encapsulated into an elastic ring. They show how the deformability and the adhesion parameters affect the leukocyte and adhesion process in shear flow. However, only a small portion of the adhesion length is allowed to peel away from the vessel wall. This constraint is not physically sound, and a more sophisticated model was developed by N Dri et al. [2003]. 

The random roughness of surfaces can be modeled by a statistical distribution, as first shown by Johnson and later much expanded by others. Using such a statistical theory, Fuller and Tabor defined an adhesion parameter which was the asperity height divided by the maximum extension an asperity could withstand before adhesive fracture. This adhesion parameter increased with roughness and elastic modulus but decreased with work of adhesion and asperity... 

The Surface energy of filler and matrix are important for the adhesion properties in composites. By calculation of the surface free energy of the composite components from Contact angle measurement, Inverse gas chromatography (IGC) or other measurements, adhesion parameters can be estimated and controlled if necessary, for particular applications. An illustration of this is given in this article. 

The pre-treatment of a filler surface changes fhe interface, and thus it is expected to affect the properties of adjacent phases extending some way into the bulk. There are examples of using the various surface modifiers such are acids and acid precursors, alkoxysilanes, organofitanates and related compounds, stearic acid and others." How the surface pre-treatment of CaCOs filler by sodium stearate changed fhe adhesion parameters in the PVAc composite is illustrated in Table 1 The adhesion parameters could be used to relate the interactions at the interface to the mechanical properties of the composite. For example, the small absolute decreases in the work of adhesion after the pre-treatment can lead to the proportionate large absolute decreases in fracture energy. 

Table 1. Comparison of adhesion parameters in PVAc composite with untreated filler (CaCOs) and pie-tieated with sodium stearate (4.5%)(CaC03-S4,5) ...

The quantities c, v, and can be measured. The first term on the right-hand side of the equation accounts for the adhesion of th suspended particles (b is the adhesion parameter), and the second term accounts for detachment of these particles under the influence of hydrodynamic forces. If bc>ap x, the adhesion processes predominate over the hydrodynamic processes, i.e., filtration takes place. If up x/v > be, previously adhering particles are removed. 

A positive effect regarding the adhesion was observed when plasticizers were added. Their effect is based on the increase of molecular mobility in the amorphous phase. Exceeding the threshold additive concentration leads to a decrease in adhesion, as with other additives discussed above. This effect is caused by a reduction of the contact area. The importance of threshold solubility is demonstrated by the addition of nonpolar vaseline oil which is miscible with PP in the whole concentration range. The increase in the vaseline oil concentration results in a monotonous rise of the adhesion parameters until cohesive fracture is reached. 

Simply stated, once a ligand has attached itself to a cell at one site, it suffers a smaller entropy loss by binding at neighboring sites. Mimicry of these biological adhesion parameters can be exquisitely modeled and tested with dendrimeric systems. Although a substantial number of linear, poly (valence) polymeric architectures (e.g., poly [acrylamides], etc.) have been tested with some success, [233-236] efforts toward the use of dendrimer technology to create multivalent ligands for these purposes are in their infancy. 

Additionally, the obtained values of the B adhesion parameter using the Pukanszky model [81, 82] varied from a minimum of 1.74 to a maximum of 21.45 for the studied samples. These findings confirmed that the nanofillers introduce a better interfacial interaction to the recycled polymers. Moreover, the calculated (adhesion) using the Sato-Furukawa model [83, 84] were lower than zero. Since a better modulus is achieved by inferior values, the calculated data indicated that the small content of nanofillers introduce a significantly improved modulus in the nanocomposites from waste polymers. In conclusion, the performed analysis confirmed that the nanofillers can yield considerable interfacial interaction with waste polymers. As known, the greatest advantages of nanocomposites, such as modulus and strength, are produced via perfect interfadal adhesion between the nanoparticles and waste polymer matrices. 

Table 5.122 Adhesion parameters (c = biomass growth constant, = adhesive force,...

The values of adhesion parameters which were calculated from the kinetic curves (Fig. 12) of adhesion of conidia of different microscopic fungi spores are collected in Table 12. 

TABLE 10 Adhesive parameters of interaction for polyethylene and cellophane at different temperatures and relative humidity 0 = 10%... 

TABLE 11 Adhesive parameters of conidia for polyethylene at different humidity and constant temperature 10°C... 

TYPICAL ADHEREND AND ADHESIVE PARAMETERS THROUGH AN INTERFACE... 

In Table 1 a typical set of adherend and adhesive parameters are given. The values given are ranges from various sources. 

Figure 4 Relative adhesion as a function of the adhesion parameter (equation 20) for various silicone elastomers contacting rough PMMA. The relative adhesion is the ratio of the rough value divided by the smooth (a = 0) value. The normalization is quite effective if the peeling velocities are comparable ...

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