A phosphorous/nitrogen-containing flame retardant with UV-curing for polyester/cotton fabrics

Polyester/cotton (PET/CO) fabrics usually burn more violently than single-component fabric due to significant differences of two components as well as “wick effect” during combustion process. Hence, it is very challenging to impart PET/CO fabrics excellent flame retardancy. In this work, a new monomer (ethoxy piperazine (phenyl) phosphoryl ethyl methacrylate, EPPEM) containing multiple unsaturated double bonds was synthesized. As EPPEM contained varied synergistic flame retardant components of phosphorus, nitrogen, and benzene ring, it was expected to form a dense cross-linked network structure on the surface of the fabrics by UV curing to prepare PET/CO fabrics with good flame retardancy and washing resistance. The limiting oxygen index (LOI) value of treated PET/CO fabrics increased up to 27.2% from 17.8% of control sample, which still reached 26.6% after 25 laundering cycles, indicating excellent flame retardancy and water-laundering resistance. Raman spectroscopy, thermogravimetric analysis coupled with Fourier transform infrared analysis and thermogravimetric mass spectrometry indicated that EPPEM promoted the production of more non-combustible compounds during pyrolysis process, such as H2O and CO2. Furthermore, EPPEM decomposed to produce acidic substances which promoted dehydration and coke formation of PET/CO fabrics, thereby preventing exchange of heat and combustible gas. On the basis of the results, a two-phase flame-retardant mechanism of EPPEM/UV-curable system for PET/CO fabrics was proposed.