Formation of Very High Modulus Graphite Fibers from a Commercial Polyacrylonitrile Yarn.
Technical rept. Dec 66-May 68,
AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OHIO
Pagination or Media Count:
A commercial yarn containing at least 99.5 ACRYLONITRILE MOIETIES WAS STABILIZED AND THEN DIRECTLY GRAPHITIZED. Experimental parameters included preparation of yarn with and without size, variations in yarn twist, stabilization conditions, graphitization atmosphere flow rates and directions, temperature, tension, and exposure time. A SUBSTANTIAL NUMBER OF THE EXPERIMENTS GAVE GRAPHITE FIBERS WITH HIGHER TENSILE STRENGTH AND MODULI OF ELASTICITY THAN THOSE OBTAINED FROM ANY OTHER POLYACRYLONITRILE YARNS UNDER SIMILAR CONDITIONS. A critical step in use of the yarn was the complete removal of spinning size prior to the stabilization oxidation treatment. Density and tensile strength of graphite fibers were found to increase with the modulus. However, the density is more dependent on graphitization temperature and is practically constant at any graphitization temperature regardless of the moduli. Density does not change with the tensile strength. Strain capability of the fibers decreases as the modulus increases. More than 20 of the samples had tensile strengths between 300,000 and 374,000 psi and moduli of 63 to 112 million psi at densities of 1.79 to 2.13 gcc. Author-PL
- Industrial Chemistry and Chemical Processing