Carbon Coating of Nextel 550 and 720 by Pitch–Toluene Pyrolysis
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The carbon coatings on Nextel 550 TM and 720 TM were studied in batch (furnace) and continuous (solution fiber coating apparatus) modes, and in an inert atmosphere. Ashland Aerocarb 240 TM pitch in toluene was used as the precursor material for carbon coating. The effect of processing variables (i.e., pitch concentration, Nextel fiber sizing, and oxidative curing) was studied. Characterization was done by tactile, scanning electron microscopy (SEM), and thermal gravimetric-differential thermal analysis (TG-DTA). Coating adherence, thickness, and uniformity were investigated. Applied carbon coatings adhered well onto the filaments ; however, the thickness and uniformity of the carbon coatings were not good, mainly because of melting and wicking of the pitch inside the tow prior to pyrolysis.