Biodegradable materials of poly(l-lactic acid): 1. Melt-spun and solution-spun fibres

Poly(l-lactic) PLLA fibres with a high degree of molecular orientation and crystallinity were produced by hot-drawing of the melt-spun and solution-spun fibres. Solution-spun fibres show better tensile properties as compared with those of the melt-spun fibres. This may be caused by a lower number of entanglements trapped in the solution-spun fibres. The highest values of the tensile strength found for PLLA fibres in the present study were 0.5 and 1.0 GPa for the melt-spun and solution-spun fibres, respectively. Tensile strength of PLLA fibres increases with the draw ratio, and above a certain molecular weight, also with molecular weight of the polymer. Tensile strength was found to be strongly dependent on the drawing temperature which may be associated with the occurrence of two crystal modifications.