Thermal degradation study for manufacturability of polyetheretherketone/hydroxyapatite bone implant composite

Abstract

Polyetheretherketone (PEEK) is a semi-crystalline, high temperature resistant, FDA approved polymer, attracted many engineering and medical research practitioners due to its excellent mechanical and biological properties. PEEK has comparable mechanical properties to natural bone and its polymeric constituent. PEEK has been identified as one of the high temperature(Tm= 373°C) polymers with excellent thermal, chemical and radiological inertness. High temperature resistance, good Young's modulus and biological inertness of PEEK attract it to be a prominent bone implant material. Metallic bone implants have been surpassed slowly by PEEK composites. However, PEEK is found to be inferior in rigidity to natural bone due to its limited Young's modulus. Hydroxyapatite (C10(PO4)6(OH)2), a bone inductive and ceramic reinforcement is extracted from egg shells by thermal processing to strengthen PEEK matrix of the proposed bone composite. Upon several delimiting studies, ceramic constituent is limited to 40% by weight. The combination of constituents being newer, an exhaustive study on thermal stability of the composite has been carried out at ARCI, IICT and KELVN Hyderabad. Thermal gravimetric analysis (TGA), Derivative thermo gravimetric analysis (DTG) and Differential Scanning Calorimetry (DSC) were the sources of analysis. TGA, DTG and DSC have been used to evaluate percentage of weight loss, peak degradation temperature and melting temperature respectively. Degradation of the composite was found to increase with the percentage of PEEK in the composite. The study has been conducted beyond the melting temperature of the PEEK and up to 600°C. Degradation of the composite has been showing an inverse relation with rate of heating. Maximum percentage of mass degradation 28.7% of the total weight was recorded in structurally superior PEEK/HA 80/20 composite at a rate of heating 10C/min as against 33.9% in pure PEEK.