Characterisation of surface abrasion phenomena on poly(methyl methacrylate) surfaces

The paper describes an experimental study of scratch deformation, conducted using a modified pendulum sclerometer, on a poly(methyl methacrylate) (PMMA) surface. It is shown that the depth of a scratch is a crucial parameter determining the damage mode, and that the variation of imposed depth extends the range of the observed generic deformation behaviour associated with a particular scratch velocity and nominal indenter geometry. It would appear that imperfections in the tip geometry (the tip defect) might be a contributing factor to the variation in response as a function of depth. In addition, a group of ‘velocity transitions’ are presented for the same polymer, which indicate the influence of the imposed velocity, and the consequent thermal effects on the nature of the perceived damage. The appearance of polymer melting at very high sliding velocities is also described, as are initial attempts to correlate the extent of this behaviour with the thermal properties of the indenter material.