Effect of Nitrogen Dioxide on Strength and Heat Resistance of Poly-p-Aramid Fibers

Low-temperature oxidation in air of domestic poly-p-aramid complex threads based on poly(p-phenylene terephthalamide), i.e., terlon, Rusar, and Rusar NT, that were nitrated beforehand by nitrogen dioxide was studied comprehensively by EPR and IR spectroscopy, thermoanalytical methods (TA, TMA), and scanning electron microscopy (SEM). Mechanisms of nitration and destruction of poly-p-aramid complex threads were proposed. The nitrosyl nitrate form of nitrogen dioxide was proposed as the oxidation initiator. The polymers were destroyed by degradation of N-nitrosoamides, N-nitrocompounds, and N- nitrites, i.e., nitration products of terlon, the main component of the thread. IR spectroscopy found that the major products of aramid thread nitration were esters and carboxylic acids.