AbstractThe flame‐retardant properties and the thermal behavior of cotton cellulose finished with THPC‐amide, THPOH‐amide, THPOH‐NH3, and THPC‐cyanamide were investigated before and after five washes. Phosphorus and nitrogen content, N/P ratios, and total add‐on of finish were determined. Flammability properties were evaluated by the 45°C angle, the vertical strip, and oxygen index tests. Differential scanning calorimetry and thermogravimetric analysis were used to study the thermal behavior of the fabrics during pyrolysis. Infrared spectra of samples before pyrolysis and at significant points in the pyrolysis reaction were used to obtain further information regarding the pyrolysis reaction. The THPC‐amide, THPOH‐amide, and THPC‐cyanamide finishes appeared to react in a similar manner to impart flame‐retardant properties to the fabrics. During pyrolysis, the finished fabrics apparently decomposed first by an acid catalyzed dehydration and chain breakdown. The second step of the pyrolysis probably involved phosphorylation of the C‐6 hydroxyl of the anhydroglucose unit occurring around the temperature range of 345°–350°C. The final step was char formation. The THPOH‐NH3finished fabric decomposed with a strong exothermic reaction under nitrogen which suggested that the reaction was initiated by a base catalyzed dehydration and chain breakdown. This seemed to be followed by phosphorylation at the C‐6 hydroxyl of the anhydroglucose units and then char formation. An inverse relationship between ΔHand the residue remaining after pyrolysis was observed. ΔHwas also linearly related to the N/P ratios. All of the fabrics except the TPHC‐cyanamide‐finished fabric had good flammability
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