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synopsisThe pyrolysis of acrylic fiber up to 400°C in an inert atmosphere at 1 ' and G°C/min was studied by means of thermogravimetric and differential thermal analysis. The exothermic reaction occurring at 180-300°C was shown to be due to the reaction of nitrile groups by comparing the extent of exotherm with the number of nitrile groups present, determined by infrared spectroscopy. In addition, results of single-fiber tensile measurements, density, and elemental analysis of the pyrolyzed fibers are interpreted in terms of possible molecular structures. The gases evolved on pyrolysis were analyzed for both ammonia and hydrogen cyanide and the liberation of ammonia was attributed to a termination reaction of the polymerization of nitrile groups. The critical conditions necessary for the production of high strength and modulus carbon fiber are discussed briefly in relat.ion to the chemical changes occurring on pyrolysis.

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