Preliminary laboratory experiments were carried out to obtain some information on the nature of potential carbon fiber emissions resulting from the machining and incineration of graphite/epoxy composites. Examination of residues by scanning electron microscopy following exposure of graphite fiber products in a laboratory furnace showed the high resistance of graphite fibers to combustion at temperatures up to 1000C. Resins and binders in the composites are destroyed rapidly at elevated temperatures, but one can predict that the disposal of composite waste materials by conventional refuse incineration would result in the release of large amounts of both intact and partly degraded and thinned graphite fibers. In other experiments, dusts generated by sawing and drilling of graphite/epoxy composites contained large numbers of fibers free of the resin matrix and generally about 50 to 100 micrometers in length. There was also evidence of longitudinal cleavage of some fibers by sawing; the potential thus exists for the formation of more respirable fiber fragments with diameters smaller than those (about 6 to 8 micrometers) established in the fiber manufacturing process.

"EPA-600/2-79-196." EPA program element no. 1AD712B BE-009 (FY-79). Includes bibliographical references (page 7).