The spun yarn may be drawn several times its original iength. This drawing is the strengthforming structural change which adapts polypropylene to a wide range of utility in the textile field.
The drawing ratio has a considerable influence on the mechanical properties of fibres, and the maximum ratio is desirable. The maximum drawing ratio decreases moderately with increasing spinning draft, however the maximum drawing breaks the influence of spinning draft to mechanical properties of fibre, and gets to high Young's modulus of 600kg/mm2.
The thermal treatment carried out in 120_??_140°C for few minutesimproves the thermal dimensional stability of fibres.
