Erosive wear of polymer surfaces by steel ball blasting

Abstract

The erosion behaviour of a variety of polymeric materials has been studied using steel balls at 57 m sec⁻¹ in an air-blast rig. It is shown that the softer polymers (polyethylene, polypropylene, polybutene-1) exhibit an incubation period prior to stabilizing to a linear erosion rate, here defined as reduction in thickness per testing time. The more brittle polymer, polystyrene, on the other hand, shows no incubation time and possesses the highest erosion rate. Further effects can arise from the morphology of semicrystalline polymers. In particular, it was found that a coarse spherulitic microstructure in polypropylene wears much faster than a fine spherulitic one. A decrease in testing temperature generally increases the wear rate. The individual mechanisms of erosive wear are illustrated by SEM micrographs of the worn surfaces. It is suggested that a “brittleness index” of the form (hardnessH/fracture energyG _Ic) is a good indicator for the erosion resistance of polymeric materials.