ABSTRACTThe combination of gas-phase and condensed-phase action will contribute to high quality flame retardant. A novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based flame retardant (DOPO-DOPC), which contains carbon source was synthesized in favor of conducting the effect of gas-phase as well as promoting the char formation in condensed-phase. The chemical structure of DOPO-DOPC was characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). DOPO–DOPC was used as an additive in poly(ethylene terephthalate) (PET) and epoxy resin (EP). The flame retardancy of PET/DOPO-DOPC and EP/DOPO-DOPC composites were studied by limiting oxygen index (LOI) and UL-94 test. The results showed that the incorporation of DOPO–DOPC into PET or EP could obviously improve their flame retardancy. The LOI values of modified PET or EP, which contained 10 wt % DOPO-DOPC reached 42.8 and 31.7%, respectively. The thermogravimetric analysis (TGA) results revealed that DOPO–DOPC enhanced the formation of char residues. The Laser Raman spectroscopy (LRS) was used to investigate the carbon structure of thermal oxidation residues. Because of the combination of the gas phase flame retardant effect of DOPO moiety and the promoting formation of char residues in condensed phase, the PET and EP composites exhibited significant improvement toward flame retardancy. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44639.

The empirical polarity parameter ET(30) was determined for polyethylene terephthalate (PET) fiber and five phosphorus flame retardants by UV–Vis absorption spectrum of solvatochromic probe. To investigate the interaction between flame retardant and PET fiber during the finishing process, the partition coefficients K of these flame retardants between water and PET fiber were determined and an interesting linear relationship between lnK and ET(30) of the flame retardants was obtained, suggesting ET(30) is definitely an excellent estimation of the interaction of flame retardants with PET. Additionally, the thermodynamic criterion of this finishing process, standard Gibbs free energy of transfer of the flame retardants from water to PET fiber, ΔGt0(FR,H2O→PET), was found to linearly correlate with ET(30) of the flame retardants as well, ΔGt0(FR,H2O→PET) = 0.3664∗ET(30)(FR) −18.60 (R2 = 0.9168), demonstrating polarity of flame retardant is an important and determining factor for its fixation on PET fiber. This work may provide theoretical guidance for choosing flame retardant finishing agent more compatible with PET fabric.Download high-res image (231KB)Download full-size image