Manufacture and characterization of free-standing epoxy-polyester films

The present investigation analyzes the deformation behaviour under static and dynamic loading conditions of electrostatically sprayed epoxy-polyester powder coatings by local and uniaxial tests, trying to account for the separate contribution of the raw polymeric material alone and of the adhesion to the underlying metal substrate. First, thermo-rheological properties of the basic material (i.e., the thermosetting powder paints) were characterized by differential scanning calorimetry (DSC) and rheometry. Secondly, free-standing films were manufactured by electrostatic spraying of the thermosetting powders onto stainless steel substrates pre-coated with an intermediate layer of silicon-based heat curable release coating. The resulting free standing-films were macroscopically characterized by combined dynamic-mechanical analyses (DMA) and tensile tests. Finally, local mechanical characterization of the coating performance was carried out by micro-scale depth sensing scratch and indentation on coatings 'free-standing' and 'rigidly adhering' onto metal substrate. The experimental findings show the different mechanical behaviour of the polymeric coatings, whose thermal, rheological, dynamical properties were fully characterized, when deposited on untreated or pre-treated substrates as well as on intermediate layers of release coating, thus contributing to better understand how much of the coating properties are ascribable to the material chosen or to the interfacial adhesion between coating and substrate.