Enhanced toughness of hydroxyapatite–poly(ethylene terephthalate) composites by immersion in water

Abstract

Water-soluble poly(ethylene terephthalate) bearing carboxylate groups on 14–22% of its phenylene moieties were coprecipitated with calcium ion and phosphate ion in water at room temperature, 70 °C, and 90 °C to obtain the composites of hydroxyapatite and the polymer. Composite powders with inorganic weight fractions of 30%, 50% and 70% were prepared to explore the effects of the inorganic weight fraction on the water resistance of the composites. The composite powder was compressed with hot pressing at 120 MPa and 120 °C. The compacts showed bending strengths of ∼42 MPa and elastic moduli of ∼4.2 GPa. After immersion in water for 1 week at 37 °C, the bending strengths of the compacts coprecipitated at 90 °C, containing 30 or 50 wt% hydroxyapatite, were ca. 70% of those of the pristine compacts. Moreover, the compacts with the inorganic weight fraction of 50% immersed in water did not break into two pieces in the bending test. The strain at break and the fracture energy were four times larger after immersion in water. Therefore, the immersion in water improved the toughness of the composite of hydroxyapatite and the carboxypolyester.