The Effect of Bubbles at the Interface on the Adhesion of Polyethylene to Metals

By use of a blowing agent bubbles of a few hundred microns diameter were introduced at the interface of copper and steel substrates coated with low density polyethylene. The presence of the bubbles leads to an improvement in peel strength. An explanation is put forward in terms of a suggested stress perturbation produced by the bubbles which leaves the interface itself relatively lowly stressed and leads to the expenditure of work in plastic deformation of the polymer away from the interface. Support for the explanation was obtained by photoelastic study of a model system and by scanning electron microscopy of the peeled surfaces.