Kinetic Analysis, Solid Residues and Volatile Products of Pyrolyzing Nomex Insulation Paper in Nitrogen and Air Atmosphere

This paper studies the pyrolysis mechanisms of Nomex insulation paper in nitrogen and air atmospheres. The Nomex insulation paper is composed of 93% poly (m-phenylene isophthalamide) (PMIA) fibers and 7% inorganic substances based on elemental analysis. Using the thermogravimetry, it is found that the pyrolysis behaviors in nitrogen and air are similar below 770 K, with large discrepancies identified in the temperature range of 770–1073 K. The peak mass loss rate in air is 9 times higher than that in nitrogen. The kinetic analysis shows that the average activation energy (\(E\)) in air is lower than that in nitrogen by 32% when the temperature is higher than 770 K, indicating a lower thermal stability. The PMIA fibers are found decomposing more seriously in air using SEM. Below 770 K, the functional groups of two atmospheres are mainly produced by the breakage of amide bonds and formation of aromatic nitrile. Unlike nitrogen, the organic substances in the solid residue are mostly oxidized at 1073 K in air. Consequently, the maximum productions of H₂O, CO₂ and CO in air are nearly 5 times higher than those of nitrogen, and the HCN generated during pyrolysis is further oxidized to NOx in air. Combining with the results of Py-GC/MS, it is inferred that the small molecules generated by the degradation of PMIA molecular chains, especially the benzene rings, will experience oxidization reactions in air atmosphere, with large amounts of H₂O, CO₂, CO and NOx produced.