Flame-retardant and anti-dripping coating for PET fabric with hydroxyl-containing cyclic phosphoramide

To prepare flame-retardant anti-dripping of polyethylene terephthalate (PET) fabric, a hydroxyl-containing cyclic phosphoramide named as 2,2-dimethyl-1,3-propanediol-(2′-hydroxyethyl) phosphoramidate (DPHP) was synthesized and was coated on PET fabric by dip-coating technology. The flame retardancy, non-dripping performance and thermal stability of DPHP-coated PET fabrics were investigated by limiting oxygen index (LOI), vertical flammability, cone calorimetry tests and thermogravimetric analysis (TG). It was found that DPHP can enhance the char forming for PET, which endows the PET fabrics with excellent flame retardancy and non-dripping behavior. Although the LOI had a little increase with low content of DPHP (9.6 % weight gain), the non-dripping performance was observed. With the continuous increase of DPHP content, LOI was increased to 27.6 % and the damaged length was only 7.9 cm. After coating with DPHP, the char-forming ability of PET fabrics was improved and heat release was significantly reduced during the combustion. By analyzing the char residues by SEM-EDX, worm-like appearance and a large amount of phosphorus-based compounds were found in the char residue, indicating that DPHP owns efficient condensed-phase flame-retardant action for PET fabrics. This work suggests that hydroxyl-containing cyclic phosphoramide as a flame retardant is an effective way to develop flame-retardant and anti-dripping PET materials.