POLYBUTYLENE MONOFILAMENTS .1. PREPARATION AND PROPERTIES

Monofilaments were produced from a variety of commercial polybutylenes. Processing variables investigated were the cooling-water temperature, haul-off rate, and screw speed. The crystallinity and birefringence of the monofilaments were measured, and wide-angle X-ray diffraction was used to indicate the extent of crystallite orientation. Tensile properties and elasticity were also measured. Except for low crystallinity grades and a highly nucleated variant, crystallinity increased with increasing water-bath temperature, which resulted in increased modulus and elasticity. Break strain and break stress were reduced. For most samples, birefringence was almost independent of bath temperature, although increases with temperature were observed for three grades. Over a wide draw-ratio range, orientation behaviour was shown to be complex and dependent on grade. Increased draw ratio generally increased break stress and modulus and decreased break strain. Stress at break was related to birefringence, although the nature of this relationship varied. Highly elastic materials showing up to 90% recovery have been produced for certain grades by using appropriate processing conditions. High elasticity is associated with the combination of a highly developed crystalline phase, a high amorphous orientation, and a moderate crystalline orientation.