- Author
- Sekiguchi, Y. | Shafizadeh, F.
- Title
- Effect of Inorganic Additives on the Formation, Composition, and Combustion of Cellulosic Char.
- Coporate
- Montana Univ., Missoula
- Journal
- Journal of Applied Polymer Science, Vol. 29, 1267-1286, 1984
- Contract
- NB81NADA2066
- Keywords
- cellulosic materials | thermal analysis
- Abstract
- At temperatures above 300 Deg. C the glycosyl units of cellulose are simultaneously depolymerized to a tar and decomposed to a char by evolution of H2O, CO, and CO2. When the glycosyl units are depleted, a stable char is formed containing about 30% aliphatic and 70% aromatic components. The aliphatic component is formed first, but on further heating is converted to polycyclic aromatic structures. The chars formed at lower temperatures are more combustible because the aliphatic component of the char is highly pyrophoric and is oxidized almost at the same temperature at which it is formed (~360 Deg. C). The aromatic component, however, is less reactive and is oxidized at ~520 Deg. C. Consequently, the chars formed at higher temperatures are less combustible. It has been shown that (NH4)2HPO4, which is a well-known flame retardant and smoldering inhibitor, lowers the pyrolysis temperature and increases the char yield by accelerating the decomposition reactions. This affects the composition of the intermediate chars but the final products have about the same composition irrespective of additives. (NH4)2HPO4 also lowers the rate of oxidation of the aromatic component and the corresponding heat release. NaC1, which is an enhancer of smoldering combustion, has a slight stabilizing effect on pyrolysis of cellulose. It lowers the oxidation temperature of the aromatic component and dramatically increases its rate. The corresponding heat release is also increased due to complete oxidation to CO2. The rate of oxidation calculated from the dynamic thermal analysis data is more than tripled by NaC1 and significantly reduced by (NH4)2HPO4.