ENHANCEMENT OF THE MECHANICAL-PROPERTIES OF POLYLACTIDES BY SOLID-STATE EXTRUSION .2. POLY(L-LACTIDE), POLY(L D-LACTIDE), AND POLY(L/DL-LACTIDE)/

Polylactides with various degrees of chain regularity-crystalline poly (L-lactide); amorphous poly(L/D-lactide), and amorphous poly(L/DL-lact ide)-were processed into high-strength, high-modulus resorbable rods u sing solid-state extrusion through a conical die. The rods with a high ly fibrillated structure had flexural strengths at a yield of up to 21 5 MPa and flexural modulus of up to 13.7 GPa. The initially amorphous poly(L/DL-lactide) developed approximately 25% of crystallinity after solid-state extrusion. Poly(L/D-lactide) remained amorphous independen tly of the treatment procedure applied. The shear strengths, flexural strengths, and flexural moduli of the solid-state extruded rods increa sed with increasing draw ratio. For the semicrystalline materials, sol id-state extrusion enhanced the crystallinity. The achievable draw rat ios during solid-state extrusion, and in consequence the final mechani cal properties, were lower for poly(L/D-lactide) and poly(L/DL-lactide ) than for poly-(L-lactide). (C) 1996 John Wiley & Sons, Inc.