Mechanistic Aspects of Flame Retardancy in Cotton Cellulose

Abstract

A series of cotton fabrics treated with different levels of THPOH-NH₃ was examined by pyrolysis-mass-spectrometry and thermogravimetry. Small amounts of THPOH NH₃ lowered the pyrolysis temperature and increased the char yield, but larger amounts of the flame retardant effected little additional change. Identical kinetic parameters character ized the formation of all cellulose pyrolysis products from a given fabric; these parameters were very similar for all the treated fabrics. Small amounts of THPOH-NH₃ greatly decreased the fractions of anhydroglucoses (levoglucosan, 1,6-anhydroglucofuranose, and 1,4:3,6-dianhydroglucopyranose) in the volatile pyrolysis products but increased the fractions of furans (hydroxymethylfurfural, furyl hydroxymethyl ketone, and levoglucosenone). Larger amounts of THPOH-NH₃ decreased the furan fractions. Add-on of flame retardant had relatively little effect on fractions of carbon dioxide and carbon monoxide. The water fraction increased continuously with add-on to a maximum at 21% of THPOH-NH₃. Flammability (oxygen index) was closely correlated with the molar fraction of nonfuels (water and carbon dioxide) in the volatile products. Mechanisms of flame retardancy are discussed.

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