ULTRAHIGH MODULUS RODS OF THERMOTROPIC LIQUID-CRYSTALLINE COPOLYESTERS CONTAINING PARA-HYDROXYBENZOIC ACID

The properties and structure of ultrahigh-modulus rods were investigated for wholly-aromatic copolyesters (WACP's) containing 60 and 70 mol% p-hydroxybenzoic acid (HBA). The drawn rods were prepared by extensionally drawing the nematic melts extruded from a die of 1 approximately 5 mm diameter. The degree of molecular orientation in drawn rods were varied by taking extensional draw ratio (λ) as a variable at given temperatures. Changes in the structural ordering with λ values were monitored by wide-angle X-ray scattering and scanning electron microscopy (SEM). It was found that the higher modulus and the higher degree of crystallite orientation are obtained for the rods prepared by using larger-diameter dies, compared with the same value of rod diameter.