Structure and axial compressional behavior of liquid crystalline, wholly aromatic copolyester/poly(ethylene terephthalate) blend fibers

Structure and axial compressional behavior of poly(hydroxybenzoic acid-co-2-hydroxy-6-naphthoic acid) [P(HBA.HNA) : 70 %] / poly (ethylene terephthalate) (PET : 30%) blend fiber were studied using various techniques. It has been confirmed by wide-angle x-ray diffraction (WAXD) studies that the stress-induced crystallization of PET occurs in the highly oriented P(HBA.HNA) matrix during the melt-spinning of the blend. Orientation behavior of PET in the blend fiber is quite different from that in the sheath (PET) - core [P(HBA.HNA) ] type bicomponent fibers. DSC studies of the strongly annealed P (HBA. HNA), PET, and blend fibers showed that both the melting point of PET (Tm) and the crystal - nematic liquid crystal transition temperature of P (HBA.HNA) (Tc-n) in the blends were lower than those of pure PET and P (HBA.HNA) fibers. It seems reasonable to assume that both components are partially miscible. Neither epitaxial crystallization nor transcrystallization occurred in the blend fiber, when only PET was crystallized from the melt in the blend fiber. Further, crystallization rate of PET in the blend fibers was slow compared to that of pure PET. This result suggests that the crystallization of PET in the narrow space in the blend fiber is retarded to some extent. In spite of the blend of soft PET component, the axial compressional behavior of the blend fibers is little affected.