High-strength poly( l-lactide) fibres by a dry-spinning/hot-drawing process

High-strength poly( l-lactide) (PLLA) fibres (tenacity 2.1 GPa, Young's modulus 16 GPa) have been produced by dry spinning and subsequently hot drawing of PLLA ( M ̄ v = 9 × 10 5 ) from solutions in chloroform/toluene mixtures near the θ conditions where PLLA adopts an interrupted helical conformation. Ultimate fibre tenacity was dependent on drawability and final fibre cross section. Drawability improved with increasing heat of fusion, ΔH m, of the as-spun filaments, and was affected by the solvent composition, PLLA concentration in the spinning solution and preparation conditions. PLLA can exhibit an α-β crystal transition upon hot drawing. The theoretical strength of PLLA should amount to about 8 GPa as deduced from the diameter dependence of the tensile strength.