Enhancement of the mechanical properties of polylactides by solid-state extrusion. I. Poly(D-lactide)

Resorbable rods with circular cross-section were produced from poly(D-lactide) with Mv = 160,000 by solid-state extrusion through a conical die. The effects of extrusion temperature and the draw ratio/rate in the solid state on the final mechanical properties and morphology of the rods were evaluated. While the rods produced from polylactides by routine injection-moulding have bending strengths in the range of 40-140 MPa and bending moduli in the range of 2-5 GPa, the solid-state extrusion under the conditions applied led to rods with bending strengths at yield of up to 200 MPa and bending moduli of up to 9 GPa. Typically, for the highly oriented polymeric materials, the pins produced by the solid-state extrusion had highly fibrillated morphology.