Effects of milling brominated P-100 graphite fibers

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Michael E. Dillehay and Paul D. Hambourger Cleveland State University, Cleveland, Ohio 44115

(Received 10 October 1986; accepted 2 February 1987) Preliminary procedures have been developed for the ball milling of pristine and brominated P-100 graphite fibers. Because of the lubricative properties of graphite, large ball loads (50% by volume) are required. Use of 2-propanol as a milling medium enhances the efficiency of the process. The fibers, when allowed to settle from the milling medium, tend to be preferentially aligned with rather few fibers standing up. Milled, brominated P-100 fibers have resistivities that are indistinguishable from their pristine counterparts, apparently because of loss of bromine. This suggests that bromine would not be the intercalate of choice in applications where milled fibers of this type are required. It was found that brominated graphite fibers are stable in a wide variety of organic solvents.

I. INTRODUCTION Recent years have seen a vast increase in the use of carbon and graphite fibers in the aerospace industry. Due to their very high strength and low mass density, they have been used almost exclusively as structural components. But graphite is a moderately good electrical conductor, and that suggests additional applications. The electrical conductivity of graphite fibers can be further enhanced by the process of intercalation, which is the insertion of guest molecules between graphene planes. (In graphite, coplanar sheets of carbon atoms, with each atom bound to three neighbors in a hexagonal structure, are stacked in a regular way. It has been recommended to the International Union of Pure and Applied Chemists that these single carbon layers be referred to as "graphene" layers.) While almost any strong oxidizing or strong reducing agent can act as an intercalate, most intercalation compounds decompose in the presence of oxygen or water vapor. However, several of the transition metal chlorides, and recently bromine, have been shown to have appreciable environmental stability when graphite fibers are used as the host material.1 If the graphite fibers could be intercalated in a chopped or milled form, many of the difficulties that arise during that process could be eliminated. These difficulties include spooling of the fibers on nonreactive (glass) mandrels and respooling the product onto a less fragile mandrel, increased reaction time due to intercalate migration time through the spool, and limitations on reactor geometry. The high aspect ratio of the resultant chopped or milled fibers would have important advantages over graphite powders in the areas of electromagnetic shielding and reflection of radio waves. They could be incorporated into inks or paints to be sprayed onto surfaces or mixed into thermosetting plastics. J. Mater. Res. 2 (2), Mar/Apr 1987


This article reports the effects of milling upon brominated, high modulus graphite fibers. In the process the stability of brominated graphite fibers in organic milling media was also revealed.

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