|Xia, Zhiyu - University Of Massachusetts|
|Nagarajan, Ramaswamy - University Of Massachusetts|
Submitted to: Journal of Analytical and Applied Pyrolysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2017
Publication Date: 6/15/2017
Citation: Nam, S., Condon, B.D., Xia, Z., Nagarajan, R., Hinchliffe, D.J., Madison, C.A. 2017. Intumescent flame-retardant cotton produced by tannic acid and sodium hydroxide. Journal of Analytical and Applied Pyrolysis. 126:239-246. https://doi.org/10.1016/j.jaap.2017.06.003.
DOI: https://doi.org/10.1016/j.jaap.2017.06.003 Interpretive Summary: Tannins, natural phenolic compounds abundant in many plants, exhibiting low thermal conductivity and low flammability, have inspired bionic approaches in the development of thermal insulation and/or flame-retardant materials. But, the use of tannins for cotton was limited to a dyeing fixative, and its potential for flame-retardant cotton has not been examined yet. In this study, tannic acid was found to induce the slower burning property of cotton, but alone was not effective as a flame-retardant. However, the addition of low concentrations of NaOH retarded the flammability of cotton. This remarkable synergistic effect of NaOH was explained by that the formation of intumescent char, in which fibrous char was embedded, served as a more effective barrier than the char from tannic acid alone in hindering the transfers of heat and combustible gases.
Technical Abstract: This study showed that tannic acid can form intumescent flame-retardant coating on cotton nonwoven fabric with an aid of NaOH. Tannic acid alone altered the thermal patterns of the pyrolysis and combustion of cotton and increased the char yield, but its improvement in limiting oxygen index (LOI) was not remarkable. Addition of low concentrations of NaOH enhanced the adsorption of tannic acid and catalyzed the thermal degradations of both tannic acid and cotton to further increase the char formation. The produced char showed the fibrous composite structure with blown surface char layers. This intumescent char offered effective protection against heat and flame, as evidenced by the reduction in heat release capacity by up to 82% (278 to 51 J/g'K) as compared with control cotton and the increase of LOI up to 30.2%.