Interfacial boundary strength

Applying this model to MWNT/PVA composites resulted in a predicted interfacial shear strength, t, of 348 231 MPa, about an order of magnitude higher than expected. Thus, Eq. (35.5) was modified to allow for the observed interfacial failure at the boundary between the bulk polymer and the ciystalline polymer layer (thickness = b) adhering to the MWNT surface. 

The measured tensile strength Oo- using a molded ASTM tensile specimen was used to define the boundary value at 0 = 0, i.e. o(0) = Gir. In Fig. 12.27, each material exhibits a parabolic-shaped curve suggesting transverse tensile behavior typical of the shear failure in the fiber-matrix interface. Based on Lees (32), the minimum tensile strength value for each curve approximates o(45°) for the given composite material. By substituting the value of o(45°) into Eq. (12.9), the effective interfacial shear strength value was obtained x = sin (45°) cos (45°) g(45°) = (0.707)(0.707) 0(45°) = o(45°)/2. 

In the cases of boundary lubrication described so far, it is not always necessary to invoke a change in the interfacial shear strength to account for the reduction in the frictional work. The value of T remains unchanged and it is the contact area which is reduced. There are, however, cases where true boundary lubrication is observed that is the interfacial shear strength is modified by the adsorption of suitable species. The lubrication of polyethylene terephthalate by perfluorodecalin is such an example apparently the fluid actually ingresses into the interfjge. A more illustrative example has been given by Senior and West. They sulphonated polyethylene and... 

In the present work we have found that Equation (13) adequately describes the reduction in friction of PET fibres in water and SDS/salt solutions only on the basis of the wetting characteristics of the liquid. The model can be readily extended to determine the level of boundary lubrication since the equation contains interfacial shear strength terms. In the same way it should be possible to determine the effect of plasticising substances. ... 

It is suggested that TOR having lower viscosity locates at the boundary of NR/EPDM layers, thereby increasing their interfacial strength. This was confirmed by measuring the adhesive strength (Ga) between NR and EPDM sheets with and without TOR as shown in Table 11.13. It is speculated that TOR is co-vulcanized with component elastomers, thereby increasing compatibility. 

To ensure that the detector electrode used in MEMED is a noninvasive probe of the concentration boundary layer that develops adjacent to the droplet, it is usually necessary to employ a small-sized UME (less than 2 /rm diameter). This is essential for amperometric detection protocols, although larger electrodes, up to 50/rm across, can be employed in potentiometric detection mode [73]. A key strength of the technique is that the electrode measures directly the concentration profile of a target species involved in the reaction at the interface, i.e., the spatial distribution of a product or reactant, on the receptor phase side. The shape of this concentration profile is sensitive to the mass transport characteristics for the growing drop, and to the interfacial reaction kinetics. A schematic of the apparatus for MEMED is shown in Fig. 14. 

---