Abstract: Infusible cured phenolic resin fibers of the present invention have a birefringence of at least 2.times.10.sup.-3 with the x-ray diffraction pattern of the fibers showing an amorphous halo. The tenacity of infusible cured phenolic resin fibers is significantly increased by subjecting the fibers to sufficient longitudinal tension as to cause at least about 30% elongation of the fibers. The Young's modulus of elasticity of the fibers is also significantly increased thereby. Preferably the resulting stretched infusible cured phenolic resin fibers have a tenacity of at least about 4 g./den.

Abstract: Phenolic resins employed for melt spinning fibers are modified by the incorporation therein of from about 5% to about 30% of an aliphatic nylon, whereby the melt spinning characteristics of the phenolic resins are improved and the tenacity of the melt spun fibers is increased.

Abstract: A flame resistant cloth or fabric comprising synthetic fibers prepared from resin condensation products of phenols and aldehydes which can be fiberized and cured. These fabrics may include blends of phenolic resin fibers with other fire resistant fibers such as wool, silk, polyamide fibers, polyacrylonitrile fibers, mineral and glass fibers, among others.

Abstract: High modulus oxybenzoyl copolyester fibers are produced by heating to an elevated temperature and stretching oxybenzoyl copolyesters fibers having molecular weights in the range of from 2,000 to 200,000 and melting points of at least 250.degree.C and comprising recurring moieties of Formulas I, II and III - ##SPC1##wherein n is 0 or 1; x, y and z are integers; y:z = from 10:15 to 15:10, x:y and x:z = from 1:100 to 100:1; x + y + z = from 30 to 600; the carbonyl group of Formula I is meta and/or para to the oxy group thereof; the carbonyl groups of Formula II are meta and/or para to each other; and the oxy atoms of Formula III are meta and/or para to each other; and in more than 50% of the total of sid moieties having said mentioned groups therein they are of para configuration. For Formulas I and II n is preferably 0 and for Formula III it is usually 1.

Abstract: Polyesters of para-oxybenzoyl are infusible and very resistant to acids and solvents, thus limiting the means by which such polymers can be fabricated. Such a polyester is made more amorphous, thus improving compression moldability, by subjecting it to a high temperature treatment, followed by a rapid quench. The resulting polymer has reduced crystalline orientation, as evidenced by X-ray diffraction patterns, and molded articles thereof have improved flexural strength, without adversely affecting the modulus. The thermal treatment is carried out on the polymer by heating at a temperature of at least 300.degree.C, and up to just below the decomposition temperature of the polymer, followed by quenching of the hot polymer.