Abstract
—Polyurethane (PU) adhesives are generally multiphase systems and thus naturally consist of materials or phases of intrinsically different chemical and mechanical properties. We describe here a rheological technique (annular RIM system) which has been used to alter the surface chemistry and mechanical properties, and hence the adhesion of the materials, by imposing a shear strain generated during their fabrication. The results of ATR-IR, WAXS, DMTA, HPLC, friction and adhesion measurements are described to assess the degree of phase segregation developed as a function of the shear strain. In the case of simple PU systems, both the degree of phase segregation and the adhesion were found to increase progressively with the introduction of extended shear strains. Additive [multiphase solid and liquid internal mould release (IMR) systems] doped PUs, on the other hand, exhibited a substantial attenuation in the adhesion following nominal shear strain. It is suggested that the observed effect arises from the vis...
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