Mechanical tests bond strength

The interaction of two substrates, the bond strength of adhesives are frequently measured by the peel test [76]. The results can often be related to the reversible work of adhesion. Due to its physical nature such a measurement is impossible to carry out for particulate filled polymers. Even interfacial shear strength widely applied for the characterization of matrix/fiber adhesion cannot be used in particulate filled polymers. Interfacial adhesion of the components is usually deduced indirectly from the mechanical properties of composites with the help of models describing composition dependence. Such models must also take into account interfacial interactions. 

As graduate students in the Wentworth laboratory, we were all required to use nonlinear least squares initially, sometimes with a mechanical calculator whose best feature was that it could take precise square roots. Later, as we tested the ECD method, we dropped the least-squares procedure for the simpler determination of a slope through straight lines. This was generally correct, but as we learned when the dissociative mechanism of the ECD was included, there was a need to use the complete ECD equation. Hirsch studied the temperature dependence of the ECD and sought new correlations of the electron affinities and hydrogen bond strengths. In order to obtain the thermodynamic parameters for the complexes from the data, a nonlinear least-squares procedure to include data determined by other experiments was developed [51]. This procedure was applied to the ECD data for the multistate model. 

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