The influence of elastic modulus on adhesion to thermoplastics and thermoset materials

The bond strength of epoxide adhesives having a range of elastic moduli has been measured using a variety of metals, plastics and composites. Adherends were selected that had an array of Youngs Modulus to assess the effect of both the stiffness of the adhesive and that of the adherend on the level of adhesion. Single lap shear test pieces, without surface preparation, have been used to determine the bond strength. It has been shown that good adhesion can be achieved with the adhesives on all substrates with the combinations of lower modulus adhesive and adherend, and higher modulus adhesive and adherend being particularly effective. A similar observation has been noted with the low modulus adhesives providing good bonds to low surface energy materials and the higher modulus adhesives being the choice for more active surfaces.