BIODEGRADABLE FIBERS OF POLY(L-LACTIC ACID) PRODUCED BY MELT-SPINNING

Starting with poly(L-lactic acid) (PLLA) of molecular weight 330 000, fibres were obtained through a two stage process: (i) melt-extrusion a t various collecting rates (ranging from 1.8 to 10 m min(-1), and (ii) hot-drawing at various drawing rates. The molecular weight of PLLA fe ll to about 100 000, as a consequence of the production process. Ninet y per cent of the molecular weight loss occurred during extrusion and ten per cent during hot-drawing. At fixed extrusion rate, properties o f as-spun fibres strongly depended on their collection rate. The highe r the collection rate, the higher the modulus and strength, and the lo wer the strain at break. While almost amorphous fibres were obtained a t lower collection rates (1.8 and 3.1 m min(-1)), about 30 and 38% cry stalline as-spun fibres were produced at rates of 5 and 10 m min(-1)], respectively. Moreover, the capability of fibres to sustain a further hot-drawing process, was found to be dependent on the collection spee d during extrusion. Tensile modulus of 9.2 GPa and tensile strength of 0.87 GPa were obtained for fibres collected at 5 m min(-1) and drawn 10 times. Copyright (C) 1996 Elsevier Science Ltd.