Intrinsic adhesive fracture energy

Values ofthe intrinsic adhesive fracture energy Go... 

Figure 3.15 Intrinsic adhesive fracture energy, Go, for polybutadiene/glass interfaces versus the fraction of vinylsilane in the mixture of vinyl and ethyl silanes used to treat the glass substrate surface [123].

Now, in an adhesive joint the failure plane may be situated either in the materials forming the joint or along the interface, or wander between these possible paths. Thus, the value of the intrinsic adhesive fracture energy. Go, may be expressed as a weighted mean of the various possible failure paths ... 

This work shows how the type and magnitude of interfacial forces can be deduced from the results of adhesion tests. For this simple polymer, the adhesive fracture energy is made up of an intrinsic term Go related to the interfacial forces, and a term related to the viscoelastic energy losses during testing. The viscoelastic loss can be expressed as an additive term (see Eqns. 1 and 3) or, for this system, as a multiplicative factor, Eqn. 4. Although for SBR at all normal rates and temperatures of test the viscoelastic term xj/ is much greater than the interfacial term W, W exerts a profound influence on the measured adhesion because of the multiplicative relationship. 

This is an important aspect and would at least partly explain in a manner somewhat different from the more accepted explanations why Go is generally 100 to 1000 times higher than the thermodynamic work of adhesion [48], It indicates that G E(v, T). Apart from this the interesting consideration still holds that the flexibility at the interface is inversely proportional to both the intrinsic fracture energy and to the peel adhesion strength at least where the effect of is minimized. 

To judge the intrinsic adhesion at an interface by the measured fracture energy may be misleading. For example, if an adhesive is modified by adding fillers... 

Relating Joint Fracture Energy to Intrinsic Adhesion... 

Many basic studies attempting to relate fracture energy and intrinsic adhesion have involved the detachment of lightly cross-linked elastomers, usually over a broad range of test rates and temperatures. Work expended irreversibly in stressing these joints up to the point of failure is included in the total work of detachment. To focus attention on interfacial bonding it is therefore necessary to minimize any dissipative processes in the adherends. A simple cross-linked... 

Table 3.5 Values of the intrinsic fracture energy, Go, and the thermodynamic work of adhesion, Wa, for a styrene-butadiene rubber adhering to various substrates [14,15,113]...

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