Biodegradable fibres 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 at 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 fell to about 100 000, as a consequence of the production process. Ninety per cent of the molecular weight loss occurred during extrusion and ten per cent during hot-drawing. At fixed extrusion rate, properties of as-spun fibres strongly depended on their collection rate. The higher the collection rate, the higher the modulus and strength, and the lower the strain at break. While almost amorphous fibres were obtained at lower collection rates (1.8 and 3.1 m min(-1)), about 30 and 38% crystalline 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 speed 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.