A novel multi-claw reactive flame retardant derived from DOPO for endowing lyocell fabric with high effective flame retardancy

A novel DOPO derived multi-claw reactive flame retardant (DMCFR) was designed to improve the flame retardancy of lyocell fabric. The chemical structure of DMCFR was identified by proton nuclear magnetic resonance (1H-NMR) and Fourier transform infrared spectroscopy (FT-IR). The chemical structure and elemental composition of the modified lyocell fabric were investigated by FT-IR and X-ray photoelectron spectroscopy. The vertical burning test, limiting oxygen index (LOI) and cone calorimetry were applied to evaluate the flame retardancy of the original and treated samples. The results showed that the peak heat release rate and total heat release of the flame retardant lyocell (FR-lyocell) were significantly reduced by 90.6% and 65.5% compared to control sample. In addition, the LOI value of FR-lyocell fabric was up to 33% and remained 26% even after 20 laundering cycles (LCs). The thermal stability and char-forming capacity of the samples were measured by thermogravimetric analysis, and the residual char of the treated sample was as high as 9.15% and 42.5% under air and nitrogen atmosphere respectively, which were much higher than that of the original sample. Furthermore, the flame retardant mechanism was evidenced via scanning electron microscopy (SEM), Raman spectroscopy, thermogravimetric combined with Fourier transform infrared spectroscopy (TG-IR) and pyrolysis–gas chromatography-mass spectrometry (PyGC-MS), which supported the condensed and gas phase flame retardant mechanism.Graphical abstract