The abrasive and erosive wear of polymeric paint films

Two novel methods have been used to assess the wear resistance of six different 20-70 mu m thick polymer coatings on both galvanized steel and polymeric substrates. The coatings were commercially available 'clear-coats' which are used as the uppermost layer in automobile paint systems and are intended to provide resistance to both mechanical and corrosive damage. The first wear test involves solid particle erosion and has been developed to assess the durability of monolayer thin coatings and, in this work, has been extended for the first time to multilayered systems. The second technique uses a ball rotating in a slurry of small abrasive particles to measure the abrasive wear resistance of a material. The technique allows abrasive wear tests to be performed on a sample area smaller than 4 mm(2) and examines the uppermost 30 mu m of material. These techniques circumvent the most common problem experienced in performing wear tests on thin coatings, namely the measurement of very small mass or volume changes. The thickness and glass transition temperature of each coating material were measured and the mechanical behaviour was characterized by tensile tests on the coating material alone, The erosion durability of the coatings was found to be sensitive to the nature of the substrate. A correlation similar to the Ratner-Lancaster correlation for bulk polymers was identified between the wear resistance of the coatings in the abrasion and erosion tests and the energy required to break the coatings in the tensile tests. The polymer films which had been formulated for use on flexible substrates were consistently more wear resistant than those designed for steel. (C) 1997 Elsevier Science S.A.