PLLA Based Composites with a-Tricalcium Phosphate and a PLLA-PEO Diblock Copolymer.

Hybrid composites consisting of poly(L-lactide), PLLA, or blends of PLLA with a PLLA-poly(ethylene oxide) diblock copolymer (15-30 wt%), COP, as a biodegradable polymeric matrix and of bioactive α-tricalcium phosphate, α-TCP, microparticles as dispersed phase (25-40 wt-%) were prepared by melt extrusion and their thermal, mechanical and degradation behaviour was investigated. SEM analysis of surfaces broken in liquid N2 showed a good dispersion of α-TCP in the polymer matrix. A lowering of the glass transition temperature of the polymer matrix and enhanced crystallization rates of PLLA, both from the melt and from the glassy state, were observed in the presence of COP. Ternary PLLA/COP/α-TCP composites containing about 10 wt-% of COP and 25-40 wt-% of α-TCP showed improved compressive strength and deformation at yield as compared to pure PLLA. Degradation experiments revealed that in simulated body fluid the presence of α-TCP particles promoted the formation of inorganic deposits of a poor crystalline apatitic phase on composite surfaces as compact sferoids.