DEVELOPMENT OF HYDROXYAPATITE-TITANIUM PARTICULATE REINFORCED POLYETHERETHERKETONE BIOCOMPOSITES

Abstract

Biomaterial engineering is at the forefront of the research into biomaterials for pioneering medical breakthroughs, especially in the areas of medical implants and prosthetics. In this research, the aim is to develop a polyetheretherketone (PEEK) biocomposite reinforced with hydroxyapatite (HAp) – titanium (Ti) hybrid particles by compression moulding technique, for hard tissue implants application. HAp was synthesized from cattle bone (CB), egg shells (ES) and snail shells (SS) using two different variants of the wet chemical precipitation method. The first set of samples were treated using a variant of the wet precipitation method based on the use of analytical grade concentrated orthophosphoric acid (H3PO4). The second set of samples were processed using a variant of the wet chemical precipitation method based on nitric acid (HNO3) and diammonium hydrogen phosphate ((NH4)2HPO4). The calcined cow bone, egg shell and snail shell particles and the developed HAp were characterized to ascertain the particle size, morphology, crystal structure and other properties as well as to determine the sample with optimum HAp. The selected optimum HAp sample particles of predetermined proportions were mixed with the titanium powder in inverse corresponding proportions and then impregnated into a PEEK matrix. A control was also developed without any of the reinforcement to aid comparison of the bioactivity, biocompatibility, water absorptivity, morphological, mechanical and tribological properties. These properties were evaluated using appropriate characterizations and tests including Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) analyses which were used to obtain information about the functional groups and crystalline structure of the prepared HAp particles, titanium and PEEK in the developed hybrid composites and the control. The samples were tested to determine the mechanical, physical and tribological properties and also subjected to microbiological and cytotoxicity tests to determine the suitability of the developed hybrid composites for biomedical applications. The results were analyzed and it was discovered that the HAp derived from hybrid mix of 75% eggshells and 25% snail shells treated with a mix of diammonium hydrogen phosphate and nitric acid (DAHP-NA-ES75-SS25), 100% snail shells treated with orthophosphoric acid (OA-SS) and 100% untreated calcined cow bones (CB) were found to be stoichiometric HAp with an ideal Ca/P ratio of 1.67. Generally, the samples reinforced with OA-SS synthesized HAp gave the best performance in most of the properties examined. With 5wt.% OA-SS performing best in the ultimate tensile strength (43.9 MPa), tensile modulus (394.83 MPa), hardness (72.8 HS), thermal conductivity (0.20 W/m.K), with the least bacteria load and fungi colonies in water, as well as the least bacterial load and coliforms in Simulated Body Fluid (SBF), and the least mutagenicity. Likewise, 15 wt.% OA-SS had the best impact resistance (3.78 J/mm2), while 20 wt.% OA-SS performed best in flexural modulus (2486.10 MPa) and water absorption (6.058 g), it also had the least coliform counts in water, and the least fungi colonies in SBF (15 SFU/ML). On the other hand, samples reinforced with 5 and 10 wt.% CB had the highest hardness (72.80 HS) and wear resistance (0.13 mg/cycle), respectively. Samples reinforced with DAHP-NA-ES75-SS25 exhibited the highest maximum flexural strength (83.30 MPa), SBF absorption (6.059 g), and the least cytotoxicity. Therefore, a new approach to the development of biomaterials from the blend of animal wastes, metals and polymers to achieve sustainable development by re-using wastes to produce value added products