Development and properties of polycaprolactone/hydroxyapatite composite biomaterials

Polycaprolactone/hydroxyapatite (PCL/HA) composites were prepared by two different procedures. The first one consists of a conventional blending of the polymer and the reinforcement material in an extruder. The second method consists of grafting of PCL on the surface of HA particles. This was achieved by a ring opening polymerization of caprolactone in the presence of HA, where its OH groups act as initiators. By this method, it was possible to obtain, in one step, a composite of PCL and surface modified HA. In both methods different percentages of filler were used to obtain several composites. These composites were characterized with respect to their mechanical properties, in the dry and wet state, by means of tensile tests on compression molded samples. The polymer/filler interface was analyzed by scanning electron microscopy. Water uptake and weight loss degradation experiments were also performed. An increase in the modulus for higher amounts of filler was, as expected, observed in the composites obtained by both processes. Furthermore, the mechanical properties of the materials in the wet state are considerably lower than those in the dry state. However, this difference is more significant for the composites obtained by conventional blending than for composites obtained by the grafting procedure, indicating that the later procedure can be an adequate route to reduce water susceptibility of PCL/HA composites.