Evaluation of mechanical properties and adhesion of polymer coatings by continuous hardness measurements

Abstract

Two grafted acrylic latex coatings with different glass transition temperatures-one glassy, one rubber-like-were coated onto a polyethylene terephthalate (PET) film in order to obtain new surface properties. The mechanical properties of the coatings were evaluated by continuous hardness measurements. The behaviour of the glassy coating can be defined as elastoplastic and we can analyse the indentation curves using the classic equations developed for elastoplastic materials. In the case of the rubber-like coating, the indentation curves are very different. There is no plastic deformation and the coating adheres to the indenter. We propose a model to calculate the Young's modulus of the rubber-like coating from these indentation curves. The same experimental set-up was used to perform indentation debonding tests in order to study the influence of the mechanical properties on the adherence of the coatings to the substrate. The rubber-like coating, which has weak mechanical properties, adheres to the PET substrate much better than the glassy coating.

Keywords:

• Polymer coating
• indentation
• mechanical properties
• debonding test
• adherence