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.

Abstract: Fibrous PAN material in raw or oxidized form is purified of alkali metals, particularly sodium, and alkaline earth metals by treating with an aqueous acid solution such as hydrochloric acid having a concentration of at least 0.5% by weight and preferably at least 3% and a temperature greater than 100.degree. F. and preferably at least 125.degree. F. but not greater than the temperature at which the aqueous acid solution boils, for 5-120 minutes and preferably at least about 15 minutes. An ion exchange occurs between the acid and the PAN material, and alkali and alkaline earth metal salts are formed. The PAN material is then rinsed in solvent such as deionized water which is substantially free of metallic ions at a temperature which is preferably at least about 150.degree. F.

Abstract: In a method of making carbon or graphite yarn, a bundle of single ply precursor yarns is knit into an elongated fabric to facilitate subsequent processing of the yarns. The elongated fabric is pretreated to facilitate carbonization thereof such as by being advanced in the direction of elongation thereof through a cleaning process. Thereafter the yarns remain in the form of the fabric to facilitate processing thereof through at least a carbonization step. The carbonization step may be accomplished by winding the elongated fabric onto skeins to a desired extent and then severing the fabric, following which the skeins are disposed in a carbonizing oven to at least partially carbonize the yarns. Thereafter, the fabric length on each skein may be deknitted, and the resulting bundle of single ply yarns is twisted to form a multi-ply yarn which is then fired to substantially raise the percentage of carbon in the yarns and then graphitized.