A comparative study of the thermal and dynamic mechanical behaviour of quenched and annealed bioresorbable poly- l-lactide/α-tricalcium phosphate nanocomposites

Abstract

Despite numerous reports on the degradation properties and biological efficacy of bioresorbable polymer nanocomposites intended for use in orthopaedics, there is currently limited literature addressing their thermal and load-bearing properties, which are of central importance to the successful design of these nanocomposites. Here we demonstrate that the storage moduli at 37 °C and the glass transition temperatures of quenched poly- l-lactide/α-tricalcium phosphate nanocomposites were lower than those of annealed nanocomposites while the damping factor tan δ values of the quenched nanocomposites were higher than those of the annealed nanocomposites. This was due to the highly crystalline structure of the annealed samples, as confirmed by wide angle X-ray diffraction. The higher storage moduli and glass transition temperatures of the annealed nanocomposites implies that higher energy will be generated to resist deformation with the possibility for reduced polymer chain mobility during in vivo use. Therefore, the decision as to whether to use quenched or annealed nanocomposites depends on the load-bearing conditions prevailing at the site of implantation. The storage moduli of the nanocomposites at 37 °C approached the lower range of the storage modulus for cortical bone and this may prevent stress shielding during bone regeneration.