Adhesion of polymer coatings studied by laser-induced delamination

Abstract

This paper concentrates on the laser-induced delamination technique, aimed at measuring the practical work of adhesion of thin polymer coatings on metal substrates. In this technique an infrared laser-pulsed beam is used to create an initial blister. Upon increasing the pulse intensity, the size of the blister grows, resulting in partial delamination of the film. In this work the blister profiles and the blister pressure were obtained from independent measurements. Alongside experiments, a simple model is developed to provide the equations necessary for calculating the blister strain energy, height, and the gas pressure inside the blister. The model is essentially based on an elastic behavior of the polymer film. The blister height and the blister pressure predicted by the model were confronted with the experimental observations and a fair agreement was found. The adhesion properties of the polyethylene terephthalate films on a steel substrate were characterized in terms of the maximum stress required for delamination and the practical work of adhesion. The relation between the two are discussed. Because the blister formation and subsequent delamination take place on a time scale of microseconds, it is argued that the viscous properties of the film do not manifest on this time scale and the contribution of plastic deformation of the film is rather small.