Abstract: High tensile carbon fibers are provided with a high yield process in which, after oxidation of a precursor, the fibers are first precarbonized in an inert atmosphere to to about 600.degree. C. while imparting 5-10% stretch. In precarbonizing, the fibers are intially heated in a sweeping manner with substantial volumes of hot inert gas which is extracted along with products of decomposition before the fibers are cooled to a low, non-reactive exit temperature. The arrangement minimizes redeposition of tars on the fibers and stretches the fibers in a range in which substantial off-gassing occurs. Thereafter the fibers are finally carbonized at a higher temperature with a different tension being applied, to provide a more reliable less sensitive process that enables oxidation to be effected more rapidly.

Abstract: High tensile carbon fibers are provided with a high yield process in which, after oxidation of a precursor, the fibers are first precarbonized in an inert atmosphere to to about 600.degree. C. while imparting 5-10% stretch. In precarbonizing, the fibers are initially heated in a sweeping manner with substantial volumes of hot inert gas which is extracted along with products of decomposition before the fibers are cooled to a low, non-reactive exit temperature. The arrangement minimizes redeposition of tars on the fibers and stretches the fibers in a range in which substantial off-gassing occurs. Thereafter the fibers are finally carbonized at a higher temperature with a different tension being applied, to provide a more reliable less sensitive process that enables oxidation to be effected more rapidly.

Abstract: In a method of producing purified carbonized material from polyacrylonitrile precursor material, the precursor material is initially oxidized and partially carbonized prior to purification treatment to remove alkali and alkaline earth metal impurities. Following purification, the material is substantially completely carbonized. Purification is accomplished by weaving oxidized and partially carbonized tows of the polyacrylonitrile precursor material into a fabric and thereafter contacting the fabric with an aqueous acid solution at an elevated temperature followed by rinsing with a solvent which is substantially free of alkali and alkaline earth metal ions and which is at an elevated temperature. Purification of the tows after partial carbonization thereof limits the amount of tow weight loss and shrinkage occurring after the fabric is formed.