A Thermochemical Investigation of Cotton Flame Retardance

Abstract

Differential scanning calorimetry and thermogravimetric analysis curves were obtained for cotton cellulose in the presence of both flame-retarding and nonflame-retarding compounds and evaluated quantitatively for ΔH, activation energy, total weight loss, and char remaining after pyrolysis. Twenty-three compounds were tested and were found to fall roughly into three groups: (I) those which do not undergo decomposition in the temperature interval in which cellulose decomposes (200-400°C); (II) those which decompose appreciably during or preceding this temperature range; and (III) those which do not interact in any way with cellulose. It was found that, with increasing molar add-on, heat liberated from cellulose decreased for group I, increased for group II, and was not a function of molar add-on for III. A study of the kinetics of decomposition for these systems indicates that, while the majority of reactions proceeded as a pseudo first-order process, there are several exceptions to the trend. As would be expected for a first-order process, activation energy was found to decrease with increasing flame retardancy. Further, it has been observed that the addition to cellulose of any of the compounds from the first two groups lowers the onset temperature of decomposition and the temperature at which the first major weight loss begins. This temperature decrease approaches some type of limiting value for all the compounds, and varies from compound to compound. In addition, a large increase in remaining char results from a very small add-on, and this, too, tends to approach a limiting value as add-on increases.