Polyethylene composite with hydroxyapatite

In order to obtain a bioactive material with a lower elastic modulus and ductility, Bonfield prepared a hydroxyapatite-polyethylene composite [50]. Hydroxyapatite powders can be dispersed in a polyethylene matrix up to 45 vol% without losing any ductility of the polymer. The resultant composite shows a Young s modulus value of about 3 GPa, an ultimate tensile strength of 22-26 MPa, and a fracture toughness, Kjc, of 2.9 MPa m [51]. This composite is already used clinically as an artificial middle ear bone, etc. 

Figure 10.32 TG curves of hydroxyapatite (HA)-ultra-high molecular weight polyethylene (UHMWPE) composites with different content HA particles. The legends indicate the nominal volume fraction of HA in the UHMWPE matrix.

Another application of dental composites is orthodontic archwires. One example is a unidirectional pultruded S2-glass-reinforced dimethacrylate thermoset resin. Depending on the yam of glass fiber used, the fiber volume fraction varied from 32 to 74 percent The strength and modulus were comparable with those of titanium wires. Orthodontic brackets were also made from composites with a polyethylene matrix reinforced with ceramic hydroxyapatite particles, resulting in isotropic properties and good adhesion to enamel. 

Albano C, Catano L, Figuera L et al (2009) Evaluation of a composite based on high-density polyethylene filled with surface-treated hydroxyapatite, Polym Bull 62 45-55... 

An important development of orthopaedic implants has been the development of artificial composites, which when combined with biomolecules will induce osteogenesis. The properties of hydroxyapatite (HA) materials have been studied over the years with a view to increasing elasticity. Because biocompatibility has been a problem when HA has been combined with various polyethylenes and polysulphones, polyhydroxyalkanoates (PHAs) and its chemical composites, a polymer of hydroxybutyric acid (PHB), copolymers of hydroxybutyric acid and... 

The easiest synthetic route is to use inert polymers (as above) doped with concentrated KOH(aq) (as above) polybenzimidazole (PBl) [57-61], poly(vinyl alcohol) (PVA) [44], composite polymers such as PVA/hydroxyapatite (PVA/HAP) [62], quatemized-PVA/alumina (QPVA/AI2O3) [63], PVA/titanium oxide (PVA/ Ti02) [64,65], chitosan and cross-linked chitosan [66-68], copolymers of epichlo-rohydrin and ethylene oxide [69], and cross-Unked PVA/sulfosuccinic acid (10 wt. % SSA) [70] have aU been doped with KOH and used as AEMs. Patent US5569559 [71] describes the use of polar polymers (most preferred being polyethylene oxide) doped with alkaline metal hydroxides (such as KOH), alkaline earth metal... 

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