Strong bioresorbable Ca phosphate-PLA nanocomposites with uniform phase distribution by attrition milling and high pressure consolidation

Abstract

Highly dense bioresorbable Ca-deficient HA-PLA (CDHA-PLA) and β-TCP-PLA nanocomposite materials with high (up to 80 vol%) contents of the calcium phosphate (CaP) phase and homogeneous phase distribution were prepared via attrition milling followed by high pressure consolidation at ambient temperature. The microstructure and mechanical properties of the materials obtained were studied as a function of milling time and PLA amount. Attrition milling resulted in disintegration of β-TCP powder agglomerates down to 50-150 nm, disintegration of CDHA agglomerates and refinement of 15 × 150 nm(2) CDHA nanoparticles to a size of 8 × 20 nm(2), and in a uniform distribution of the polymer component. Very high compressive strengths up to 400 MPa and high bending strengths up to 70 MPa were obtained. For both β-TCP and CDHA-based nanocomposites, the strength characteristics increased with milling time and decreased with increasing PLA content. For CDHA-based nanocomposites, attrition milling resulted in decrease of ductility while for β-TCP-40 vol% PLA the ductility increased. The observed behavior may be a result of formation of homogeneous, relatively thick (tens of nanometers), ductile PLA layers in β-TCP-PLA nanocomposites, but very thin (several nanometers) PLA layers in attrition milled CDHA-PLA nanocomposites. Degradation of compressive and bending strength in aqueous solutions was observed for all the studied CaP-PLA nanocomposites.