Durable flame‐retardant treatment of polyethylene terephthalate (PET) and PET/cotton blend using dichlorotribromophenyl phosphate as new flame retardant for polyester

Dichlorotribromophenyl phosphate (DCTBPP) was synthesized via the reaction of tribromophenol and phosphorous oxychloride and characterized by elemental analysis, IR, 1H‐NMR, thermogravimetric analysis, and differential scanning calorimetry. To impart durable flame retardancy the poly(ethylene terephthalate) (PET) fabric was treated with DCTBPP via pad–dry–thermosol fixation and the PET/cotton (50/50) blend fabric was treated with both DCTBPP and tetrakis(hydroxymethyl) phosphonium chloride (THPC)/urea precondensate via a two‐bath sequential treatment. The treated PET fabric's increased limiting oxygen index value was proportional to the increasing DCTBPP application level and showed self‐extinguishing properties at 8.1% add‐on, even after 50 washes. The blend fabric treated with 15% DCTBPP and 30% THPC/urea precondensate became self‐extinguishable and durable to 50 washes, and the treated fabric retained over 85% of its breaking strength without excessive stiffness.