Intrinsic interfacial bond strength

We have described a semiquantitative method for the measurement of the intrinsic bond strength between elastic substrates and elastic films that fail by brittle fracture. The essential features of the analysis, adapted from AR, were verified by measurements on the PET-Ni couple. The precision of the technique was 6%, in this case. The interfacial shear strength of Ni on PET doubled after ion etching, reaching about 10 kg/mm. ... 

As discussed in Chapter 2, for the formation of intrinsic adhesion forces across the adhesive/substrate interface it is a necessary, though sometimes insufficient, requirement that intimate interfacial contact occurs between the adhesive and substrate. This means that at some time in the bonding operation the adhesive must be in a liquid form, ideally with a relatively low viscosity. However, in service most adhesive joints carry some mechanical loads, even if only those resulting from the weight of the substrates, and to be able to transfer mechanical loads efficiently from one substrate to the other requires that the adhesive is a solid with an adequate stiffness and strength. These conflicting requirements mean that once the adhesive has established interfacial contact, i.e. completely wet the substrate, it must then harden or set . In this chapter the methods by which the adhesive may be transformed from a liquid state to a solid state will be considered and this classification will also be used to introduce briefly some of the main chemical types of adhesive to those unfamiliar with this aspect of adhesives technology. 

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