Structure development during melt spinning of linear polyethylene fibers

Apparatus has been developed for studying the development of crystallinity and orientation during the melt spinning of synthetic fibers. Tension in the fiber and temperature, diameter, and x‐ray diffraction patterns are measured as a function of distance from the spinneret for a running monofilament. Measurements are presented for linear polyethylene over a range of spinning variables together with other investigations carried out on the final as‐spun fibers. These data indicate that the development of crystallinity in polyethylene is controlled by a balance between increased crystallization kinetics caused by the stress in the fiber and a tendency for increased supercooling with change in any spinning variable that increases cooling rates in the fiber. The type of crystalline orientation observed, its development during the spinning process, and the changes observed with changes in spinning conditions suggest a model for the as‐spun fiber structure in which varying amounts of row nucleation and twisting of lamellar, folded‐chain crystal overgrowths occur depending on the spinning conditions. As‐spun fiber birefringence was shown to depend primarily on the crystalline orientation. Mechanical properties correlated well with c ‐axis crystalline orientation function and spinline stress.