Abstract: The present invention relates to polybenzazole fibers or filaments, staple fibers, spun yarns, and woven or knitted fabrics containing in themselves an organic pigment having heat resistance as high as a thermal decomposition temperature of 200° C. or higher, and soluble in a mineral acid and having group(s) of —N? and/or NH— in the molecule, such as any of perinones and/or perylenes, any of phthalocyanines, any of quinacridones, and any of dioxazines, wherein they have a strength retention of 50% or higher when exposed to light from a xenon lamp for 100 hours and having a tensile strength retention of 85% or higher after exposed to an atmosphere of a temperature of 80° C. and a relative humidity of 80% for 700 hours. The polybenzazole fibers or filaments, staple fibers, spun yarns, and woven or knitted fabrics can be used for cords for reinforcing rubber, sheets and rods for reinforcing cement/concrete, composite materials, sail clothes, ropes, knife proof vests and bullet proof vests.

Abstract: The present invention relates to polybenzazole fibers or filaments, staple fibers, spun yarns, and woven or knitted fabrics containing in themselves an organic pigment having heat resistance as high as a thermal decomposition temperature of 200° C. or higher, and soluble in a mineral acid and having group(s) of —N=and/or NH— in the molecule, such as any of perinones and/or perylenes, any of phthalocyanines, any of quinacridones, and any of dioxazines, wherein they have a strength retention of 50% or higher when exposed to light from a xenon lamp for 100 hours and having a tensile strength retention of 85% or higher after exposed to an atmosphere of a temperature of 80° C. and a relative humidity of 80% for 700 hours. The polybenzazole fibers or filaments, staple fibers, spun yarns, and woven or knitted fabrics can be used for cords for reinforcing rubber, sheets and rods for reinforcing cement/concrete, composite materials, sail clothes, ropes, knife proof vests and bullet proof vests.

Abstract: There is provided a polybenzazole fiber or film containing a basic organic compound in the form of a monomer or a condensate, selected from the group consisting of guanidines, triazoles, quinazolines, piperidines, anilines, pyridines, cyanuric acids, and p-phenylenediamine, m-phenylenediamine and a mixture thereof. This fiber has characteristics in that the X-ray meridian diffraction half-width factor is 0.3°/GPa or less, that the elasticity decrement (Er) attributed to change of molecular orientation is 30 GPa or less, and that the breaking strength is 1 GPa or more. This fiber can be used in staple fiber, a spun yarn, a woven or knit fabric, a felt material, a composite material, a cord, a rod, a fibrous sheet, a knife proof vest or a bullet proof vest.

Abstract: A polybenzazoleolybenzazole having a residual content of a BB-PBZ monomer of not more than 0.010 wt %, which is obtained by dehydration polymerization condensation of an AA-PBZ monomer of the formula (I) wherein Ar is a quadrivalent aromatic organic residue and X is O, S or NH, and a BB-PBZ monomer of the formula (II) W—Z—W  (II) wherein Z is an optionally substituted divalent aromatic organic residue and W is a carboxyl group or a group derived from the carboxyl group, which is reactive with —XH in the AA-PBZ monomer. Because the residual content of the BB-PBZ monomer in polybenzazole is not more than 0.010 wt %, a polybenzazole fiber having a small filament denier can be produced stably at a high speed without suffering from thread breakage during the production.

Abstract: A polybenzazoleolybenzazole having a residual content of a BB-PBZ monomer of not more than 0.

Abstract: A method for stabilizing DAR during storage, comprising storing DAR in the presence of a reducing agent having a standard redox potential of not less than -0.20 volt and not more than 0.34 volt, in a proportion of not less than 100 ppm and not more than 10,000 ppm of DAR. The present invention improves storage stability of DAR. This in turn results in easy handling and long-term preservation of DAR. Thus, a high quality polymer PBO can be easily produced and the invention greatly contributes to the industrial field.