Pyrolytic Gas Generation of Cotton Cellulose With and Without Flame Retardants at Different Stages of Thermal Degradation: Effects of Nitrogen,Phosphorus,and Halogens

Abstract

This study analyzes pyrolytic gases generated at various temperature ranges to observe changes in gas generation behavior dynamically in the process of thermal degradation. Cotton cellulose, a most flammable sample, is treated with compounds containing nitrogen and/or phosphorus as well as halogens with and without nitrogen. Each sample is heated thermogravimetrically, and pyrolytic gases are collected at various selected temperatures on the thermogravimetric curve for gas chromatographic and mass-spectrometric deter minations. The results reveal that flame retardant samples show extremely reduced amounts and fewer numbers of gas products compared with flammable samples, and some gases from flame retardant samples decrease with rising temperature, even disappearing at 500°C in the case of the (NH₄)₂HPO₄-treated sample when flammable samples show further increases. Moreover, there is a considerable amount of toxic acrolein in flammable samples, but it is not detected or the amounts are much smaller in flame retardant samples. Acetonitrile, an effective radical scavenger, is found only in samples exposed to the synergistic effects of nitrogen and phosphorus or bromine. The results confirm that flame retardation works not only to inhibit combustion and subsequent gas generation, but also to scavenge pyrolytic gases already formed, resulting in a reduction or quenching of hazardous gas generation.