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Structure development in melt spinning of poly(ethylene-co-octene) filaments with various comonomer contents



An experimental study of the spinnability and the variation in crystallinity and orientation of melt spinning of poly(ethylene-co-octene) with different contents of comonomers was carried out. The spinning behavior of these polymers was investigated under different draw-down ratios and temperatures and correlated to spinline stress. The melt-spun filaments were characterized by wide-angle X-ray diffraction birefringence, and differential scanning calorimetry. S-1 is a high-density polyethylene and S-2, S-3, and S-4 have 16, 22, and 38 wt % octene. An orthorhombic unit cell was found in all four polymers, but a dominant hexagonal structure (perhaps mesophase) was found for the highest octene level (S-4). The orientation factors for the a-, b-, and c-axis of the orthorhombic crystal structure and a-axis of the hexagonal phase were then calculated. The crystalline orientation behavior of the lower octene copolymers (S-1, S-2, and S-3) are similar and can be represented as a “row-nucleated“ structure. However, the orientation behavior of S-4 was different. The uniaxial mechanical properties were also measured. The Young's modulus and tensile strength generally increased with birefringence for all polymers. With increasing content of octene, the Young's modulus showed a decrease from semicrystalline thermoplastic toward an elastomer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 9–22, 2004