Preparation And Mechanical Properties Of Multi-Walled Carbon Nanotube And Hydroxyapatite And Poly(Ether Ether Ketone) Composites

Poly(ether ether ketone)(PEEK)has been the ideal artificial bone substitute materials,owing to its excellent abrasion resistance,chemical stability,non-toxicity,Young's modulus closely to human bones,and being suitable for long-term implantation in the human body.However,poor biocompatibility and biological activity of PEEK limit the scope of usage.Hydroxyapatite(HA),the main part of the natural bone inorganic ingredients,has good compatibility,bioactivity and bone conduction.While the mechanical properties of pure HA is poor with low strength and is unbearable load or impact,which limit in the application of the bone tissue in humans.Thus,the design of a new composite material with advantages of both HA and PEEK is great demand.Furthermore,carbon nanotubes(CNTs)are introduced into the composite with the aid of enhancing the mechanical,thermal and electrical properties.Herein in this thesis the effects of surface modification of HA and MWCNTs on crystallinity,impact strength,tensile strength,dynamic mechanical and tribological properties of composites are investigated.MWCNTs were oxidized by a mixture of concentrated sulfuric acid and nitric acid(volume ratio of 3:1)to improve their surface activity with the formation of carboxyl groups on their surfaces.Then,the oxidized MWCNTs were modified with sulfanilic acid to prepare sulfonated MWCNTs,also withN,N'-dicyclohexyl carbodiimide(DCC)as condensation agent by forming amido bond.Finally,a series of composites(MWCNTs/PEEK,HA/PEEK,m-HA/PEEK,s-MWCNTs/m-HA/PEEK)were fabricated by hot-press progressing.The morphology,crystallization properties,mechanical,dynamic mechanical dynamic and tribological properties of the composites were investigated.The following conclusions can be drawn:1)Through acidification and sulfonate of MWCNTs,the optimized factors of DCC dosage,reaction time and sulfanilic acid dosage were 0.5 g,6 h,0.3 g for 0.3 g of oxidized MWCNTs,respectively.The characteristic peak of sulfonic acid group was observed in the surface of s-MWCNTs,MWCNTs stacked loosely and dispersed well.Meanwhile,weightlessness of s-MWCNTs was maximum.2)An introduction of s-MWCNTs into PEEK matrix could improve dispersion,the tensile strength and the storage modulus of the composites compared with p-and a-MWCNTs.The crystallinity of s-MWCNTs/PEEK composites is the highest in all composites.The value of friction coefficient of s-MWCNTs/PEEK composites was decreased and is more stable than other composites.3)The adding of m-HA in PEEK matrix could improve dispersion in PEEK matrix,and increased the crystallinity,impact and tensile strength,the storage modulus of m-HA/PEEK composites.4)The addition of HA decreases the impact strength and tensile strength of composites compared with PEEK.The incorporation of s-MWCNTs produces higher improvements in the impact and tensile strength,the storage modulus and glass transition temperature than those the addition of HA composites.Wear tests have shown that the value of friction coefficient of s-MWCNTs/m-HA/PEEK composites was decreased significantly during thetest after the running-in period(about 10%).It is suggested that there was an obvious improvement in tribological properties of s-MWCNTs/m-HA/PEEK composites.