Nanoindentation response of poly(ether ether ketone) surfaces—A semicrystalline bimodal behavior

Abstract

ABSTRACTIndentation is a relatively simple and virtually nondestructive technique of assessing mechanical properties of materials by an indenter inducing localized deformation into a solid surface. The load–displacement curves, the hardness, and the elastic modulus data together with associated analysis for poly(ether ether ketone) (PEEK) surfaces are presented as a function of contact displacement. The major conclusions are that nanoindentation into the polymer show a surface hardening response that is dependent upon the contact conditions. PEEK, a semicrystalline polymer, has bimodal nanoindentation characteristics because of the presence of hard crystalline lamella within a softer amorphous phase. The bimodal character is confirmed by the load–displacement, the hardness, and the elastic modulus data. The semicrystalline polymer exhibits periodic fluctuations in mechanical properties with the increasing penetration depth. Finally, the nanoindentation is found to be a convenient method to estimate the degree of crystallinity of semicrystalline polymers. The technique may provide a convenient means to understand morphological description of the polymeric surfaces. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4401–4409, 2013