Scratch deformations of poly(etheretherketone)

This paper presents the experimental results obtained from the scratching of semicrystalline poly(etheretherketone) (PEEK). Various surface mechanical properties of the PEEK such as the hardness, the friction coefficient, the scratch depth and the prevailing deformation mechanisms are presented in the form of scratching maps, generated as a function of the contact conditions. These scratch maps provide a first order evaluation of the relative scratch resistance of materials for comparison purposes. The penetration depth dependent scratches (in the range 20–200 μm) were produced on the PEEK surfaces using rigid cones of different cone included angles and under different normal loads. The prevailing deformation mechanism and geometry of damage on the scratched polymeric surfaces were assessed using scanning electron microscope (SEM) and an optical profilometer. The deformation modes were seen to be influenced by the imposed experimental parameters; such as the contact geometry, the load, the nominal sliding velocity, the contact temperature and the contact lubrication. In addition to the common deformation mechanisms observed in amorphous polymers; ranging from elastic, ironing, viscoelastic plastic ploughing and brittle deformations, a fibrillation of the semicrystalline PEEK was seen when the polymeric surface was scratched under the severe contact conditions (the higher contact strains and the normal loads).

► Scratch deformations of unreinforced semicrystalline polymers have been identified.
► Severe contact conditions have produced fibrillation inside the scratch track of the polymer.
► Scratching maps were constructed.
► Scratch maps are complex and contain more features than amorphous polymers.
► Lubrication of the polymeric surface suppressed the brittle deformations of the polymer.