APPLICATION OF A CONTINUOUS ZONE-DRAWING METHOD TO ISOTACTIC POLYPROPYLENE FIBERS

To produce high modulus and high strength fibers, a continuous zone-dr awing (CZD) method was applied to isotactic polypropylene fibers. The CZD treatment was carried out five times at a drawing temperature of 1 50 degrees C stepwise with increasing applied tension from 14.8 MPa fo r the first treatment (CZD-1) to 207.0 MPa for the fifth (CZD-5) at a running speed of 500 mm/min. The applied tension increased. The CZD-5 fiber obtained has a birefringence of 0.0348 and a crystallinity of 67 .3%. The evidence for the existence of alpha-from in the CZD fibers wa s provided by WAXD and DSC measurements. The CZD-5 fiber has Young's m odulus of 14.7 GPa and a tensile strength of 1.08 GPa.