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The application of the blister test to an elastomeric adhesive

The blister test was described in 1961 as a means of quantifying the adhesion of relatively thin plates to flat and rigid substrates. The experimental method and various associated analyses are critically reviewed for the case of polyurethanes adhering to fairly smooth plates. This paper focuses upon two intrinsic uncertainties generally inherent in the technique; the choice of an appropriate theoretical analysis and the uncertainties involved in accurately specifying the necessary parameters required in the analysis for a thin highly elastic membrane, consisting of a polyurethane elastomer, adhered to a steel substrate. The study indicates that for the present system the fracture energy г(v), which is a function of the crack velocity v, is accurately given by: Г(v) = [P4ca4c/576Eh(1-v)2]⅓ where Pc and ac are the values of the blister pressure and blister radii respectively when Pc attains its maximum value where the crack velocity is v. E and v are respectively Young’s Modulus and Poisson’s Ratio for an elastic plate of uniform thickness, h. Other means of computing Г(v) are also reviewed. The paper also considers in detail how the various cited parameters, in particular ac, may be accurately measured and considers the magnitude of errors which may be introduced by the uncritical application of the blister method.