Structure and properties of polyacrylic acid modified hydroxyapatite/liquid crystal polymer composite

A bioactive ceramic-reinforced liquid crystal polymer compoasite was developed as a bone replacement material. Hydroxyapatite (HA) powder was modified with polyacrylic acid (PAA) and then compounded with Vectra A950 (VA) by twin screw extrusion, finally the mixture was injection-molded to prepare the HA/VA composites with different mass ratios. TEM characterization shows that PAA modification effectively broke the HA agglomeration to primary particles. FTIR and XPS analyses indicate that PAA was successfully coated on HA powder by a bridging coordination. The loading of PAA on HA surface measured by TGA was 2.2% (by weight). Rheological study shows that PAA modification increased the physical and chemical interactions between HA powder and the polymer matrix, and hence a homogenous dispersion was obtained as revealed by SEM characterization of the fractured composite surface. Tensile tests show that PAA-modified HA/VA composite (mass ratio of 20:100) has a strength of 138 MPa, modulus of 9.3 GPa, and fracture strain of 7.2%, which match those of load-bearing bone well.