Wear Behavior of PTFE–Hydroxyapatite Composite Fabricated by Hot-Press Sintering Process H. R. Zafarani • M. Abdi • M. E. Bahrololoom Received: 21 May 2013 / Revised: 24 November 2013 Ó The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg 2014 Abstract In the present work, a new biocompatible composite was fabricated by hot-press sinter-bonding of polytet- rafluoroethylene (PTFE)–hydroxyapatite composite. Furthermore, the wear properties of this composite were studied by computer-controlled pin-on-disk type tribometer in reporting volume loss per distance. The investigation was performed in three different fractions of hydroxyapatite (10, 20 and 30 wt%). In order to improve the bonding between hydroxyapatite and PTFE, and thus to increase the wear properties of the composite, the effect of adding silane-coupling agent was investigated. Furthermore, to simulate the environment of human body, some of the wear tests were carried out in the ringer’s solution. It was found that the wear resistance is improved at high load. Moreover, an optimum fraction of hydroxyapatite (20 wt%) was found in which the best wear resistance is achieved, especially at dry sliding condition. At last, the roles of the factors such as wear load, ringer’s solution, and silane-coupling agent are described with respect to their influences on the Lancaster wear coefficient. KEY WORDS: Hydroxyapatite composite; Polymers; Silane-coupling agent; Wear resistance 1 Introduction Polymers and their composites form a very important class of both biocompatible [1] and tribo-engineering materials [2]. It has been found that many inorganic particulate fillers are effective for modifying the physical and mechanical properties and hence reducing the wear rate of the poly- mers as well [3]. It has also been extensively reported that reinforcing of various polymers by fibers increases their wear resistances significantly [4, 5]. The original concept of a ceramic-reinforced polymer composite to be used as a bone substitute was introduced by Bonfield et al. [6] in 1981. Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ), a calcium phos- phate ceramic resembling bone mineral, was used in vari- ous biomedical fields such as dental materials, bone substitutes, and hard tissue pastes [7]. Hydroxyapatite can accelerate the formation of bone-like apatite on the surface of implants [8]. Polymer–hydroxyapatite composites have good bio- compatibility and high osteoconductive activity; hence, they have been developed into excellent scaffolds for biomedical applications [9]. Polytetrafluoroethylene (PTFE) polymer is a widely used solid lubricant. It is commonly used to provide a dry sliding friction coefficient l \ 0.2 on a variety of coun- terface types including stainless steel. Furthermore, PTFE is a popular biocompatible polymer with high melting point, low coefficient of friction, and a good resistance to chemical attack in a wide variety of solvents and solutions. It is commonly used in bearing and seals applications. Unfortunately, PTFE suffers from poor wear resistance and exhibits high wear rate under normal friction conditions, Available online at http://link.springer.com/journal/40195 H. R. Zafarani  M. Abdi (&)  M. E. Bahrololoom Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz, Iran e-mail: mohammad.abdi841130@gmail.com 123 Acta Metall. Sin. (Engl. Lett.) DOI 10.1007/s40195-014-0053-3