CARBON COATING OF NEXTEL-550 AND NEXTEL-720 BY PITCH-TOLUENE PYROLYSIS

The carbon coatings on Nextel 550(TM) and 720(TM) were studied in batc h (furnace) and continuous (solution fiber coating apparatus) modes, a nd in an inert atmosphere, Ashland Aerocarb 240(TM) pitch in toluene w as used as the precursor material for carbon coating, The effect of pr ocessing variables (i.e., pitch concentration, Nextel fiber sizing, an d oxidative curing) was studied, Characterization was done by tactile, scanning electron microscopy (SEM), and thermal gravimetric-different ial thermal analysis (TG-DTA), Coating adherence, thickness, and unifo rmity were investigated, Applied carbon coatings adhered well onto the filaments; however, the thickness and uniformity of the carbon coatin gs were not good, mainly because of melting and wicking of the pitch i nside the tow prior to pyrolysis.