Interfacial layer strength

Protein-polysaccharide complexation affects the surface viscoelastic properties of the protein interfacial layer. Surface shear rheology is especially sensitive to the strength of the interfacial protein-polysaccharide interactions. Experimental data on BSA+ dextran sulfate (Dickinson and Galazka, 1992), asi-casein + high-methoxy pectin (Dickinson et al., 1998), p-lactoglobulin + low-methoxy pectin (Ganzevles et al., 2006), and p-lactoglobulin + acacia gum (Schmitt et al., 2005) have all demon-... 

Fig. 14. The interfacial shear strength versus surface oxygen concentration for the A and HM carbon fibers. The large increase from the untreated (U) case to the surface treated case (S) for both fibers is due to removal of the native defect surface layer plus the addition of surface chemical groups. Removal of the surface groups with various treatments indicates that the surface chemical effect was a minor part of the overall increase. From Drzal et al.751...

Fig. 15. The interfacial shear strength for coated fibers (C) versus uncoated carbon fibers in an epoxy matrix. The finish layer increases the shear strength by creation of a brittle interphase. From Drzal et al. 7S)...

Exposure at 125 °C is very severe for this epoxy matrix (Fig. 25). Permanent changes in the matrix are noted. The interphase layer, however, acts to mitigate some of the deleterious interfacial effects and allows that system to regain a larger portion of its interfacial shear strength after moisture exposure and dehydration. The fiber without the finish layer has lost almost all of its interfacial shear strength and recovers very little after dehydration. 

The frequency of PDMS chain mobility in the interfacial layer is largely dependent on the type of silica surface. Water adsorption by the hydrophilic silicas causes the degree of chain immobilisation in the interface to decrease [107]. Sililation of the silica surface results in a significant decrease in the strength of adsorption interactions at the silica... 

In order to better understand the equilibria in the interfacial layer, it is desirable to obtain the thermodynamic parameters of the reactions involved in the surface charging processes. It is not a simple task to determine the enthalpy of specified surface reactions. At first the mechanisms of the reactions are not always clear, and secondly the situation is often so complicated that several contributions can hardly be distinguished. In the most simple case, when association of counterions does not take place (low ionic strength), one can use measurements of the temperature dependency of the point of zero charge [48-56]. The slope of the pHp c vs. reciprocal thermodynamic temperature yields the enthalpy value dependent on the assumed stoichiometry of the processes. Application of the adsorption or amphotheric or coordination concept yield [22]... 

Figure 6.14 shows that a plasma-sprayed hydroxyapatite coating on a porous titanium layer covering the titanium alloy surface (solid bars) will improve the interfacial bond strength compared to uncoated porous titanium (light bars)... 

Significant counterion transport can rapidly deplete the counterions on one side of the membrane. To sustain electroneutrality, the co-ions also deplete rapidly to produce an ion-depleted zone. Sufficiently high DC fields (>100 V/cm) can deionize a 100 pm neighborhood (the depletion zone) near the membrane. The depletion layer with low interfacial ionic strength produces the maximum possible ion current without convection and exhibits a distinct limiting-current plateau in the polarization I-V or cyclic voltammetry spectrum (Fig. 2b). This nonlinear I-V polarization is not due to electron-transfer reactions but bulk-to-membrane ion flux across the extended and depleted interfacial double layer. Its sensitivity to the interfacial charge in the depleted double layer allows sensitive conduction/ capacitance detection of hybridization with the same actuation on-chip electrodes that drive the ion current. 

This type of interfacial layer forms on rough porous substrates. The film material fills the pores and other morphologically advantageous places when there is sufficient surface mobility and wetting, and a mechanical anchor is formed. The adhesion depends on the physical characteristics (particularly the shear strength and the plasticity) of the combination of materials. 

A preferred embodiment of an oxygen transport membrane would thus have a thin porous support on the feed side to improve oxygen exchange, a thin dense separation membrane, a fine pore structure interfacial layer to facilitate oxygen transfer out of the membrane and a coarse porous support to maximize product flow and provide the structural support. An example is shown in Fig. 6.4. The coarse porous support material could be made out of inert material because it is not chemically active in the transport of oxygen. This allows the use of less expensive materials which may also have better strength characteristics. 

This chapter considers a study of two types of composites based on polyhydroxyether and graphite with various amounts of a filler. Using various methods it is possible to estimate the adhesion characteristics and interfacial layer, including its thickness and tensile strength and the interdependence between these values and the adhesion properties. The results were treated on the basis of the theory of irreversible aggregation, cluster theory of the polymer structure and fractal analysis. It was established that all the important characteristics of adhesion, the interfacial layer and mechanical properties are interconnected by the fractal dimensions of the surface of the aggregates of filler particles and of the polymer matrix, whose structure is distorted under the influence of the filler surface. 

To calculate the tensile strength of the interfacial layer o , the next equation has been used [41] ... 

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].

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