Flame retardant and hydrophobic cotton using a unique phosphorus–nitrogen–silicon-containing coating

Phosphorus–nitrogen–silicon-containing coatings consisting of tris(hydroxymethyl)phosphine oxide (THPO), 3,5-diamino-1,2,4-triazole (guanazole), and polydimethylsiloxane (PDMS) were prepared via a simple spraying deposition technique and applied to the cotton fabric to impart flame retardancy and hydrophobicity. SEM image reveals that THPO/Guanazole/PDMS-coated fabric has a rough surface and XPS spectra confirm the composition of the coating on the cotton surface. Direct flame testing indicates that the as-prepared coating can protect the cotton from burning. The limiting oxygen index increased from 18.0% for the uncoated fabric to 32.0% for the THPO/Guanazole-treated sample and 27.0% for the THPO/Guanazole/PDMS-treated sample. Furthermore, with additional THPO/Guanazole, there was a gradual reduction in PHRR values, 60% (79.0 kW/m 2 ) for C2 and 76% (48.2 kW/m 2 ) for C3 lower than that of untreated cotton. After hydrophobic treatment of C2 with PDMS, the PHRR is reduced to 127.5 kW/m 2 (35.5% for C2-PDMS). Additionally, the coated cotton displays impressive hydrophobicity with a water contact angle of 133°. This unique approach provides a facile and effective flame retardant and hydrophobic treatment for cotton fabric.