Abstract
Fibers of linear low density polyethylene(LLDPE) having melt flow rate 45 and 50 (g/10 min), which were polymerized by metallocene catalyst and Ziegler-Natta catalyst, respectively, were produced by high speed melt spinning method in the range of take-up velocity from 1 to 6 km/min. The change of fiber structure and physical properties with increasing take-up velocity was investigated through the birefringence, wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), Rheovibron, and Fafegraph-M. The birefringence increased linearly with increasing take-up velocity, and that of LLDPE(45) was higher than LLDPE(50). With increasing take-up velocity, the crystal orientation of LLDPE transformed a-axis orientation into caxis orientation. In dynamic viscoelastic behavior of LLDPE(45) fibers by the high speed spinning, the intensity of crystalline relaxation peak was decreased and crystalline relaxation temperature shifted to lower. But that of LLDPE(50) cannot be observed. Tensile strength and initial modulus were increased and elongation was decreased with increasing take-up velocity. LLDPE(45) fibers was preferred to LLDPE(50) in mechanical properties because of increment of crystal and amorphous orientation factor. The change of birefringence with take-up velocity was closely related to both initial modulus and tenacity uniformly.
