Flame Resistance Modification Of Phosphorus-nitrogen Based Flame Retardant On Silk Fabrics

In this paper, two systems of phosphorus-nitrogen contained compounds were mainlydiscussed to modify silk fabric for flame retardant properties.One method was synthesis of a new water soluble flame retardant containingphosphorus and nitrogen in one single compound. The synthesis process was as follows:phosphorusoxychloride, absolute methanol， monoethanol amine and methacryloylchloride were used as raw materials, absolute etheranhydrous and methylene dichloridewere used as solvent, triethylamine was also added as acid binding agent. Then a newwater-soluble flame retardant methacryloyloxy ethyl dimethyl phosphoric amidecontaining nitrogen-phosphorus was obtained. It was confirmed by IR spectra,1H NMR,13C NMR and31P NMR. Then this compound was grafted onto silk fabrics viacopolymerization method initiated by potassium persulfate. The optimized graftingtechnological parameters were investigated by means of single factor experiments, asfollows: the pH value was adjusted to3.5; the concentration of the initiator potassiumpersulfate (KPS) was3%(on the weight of monomer,owm); the liquor ratio was1:30; thereaction temperature and time were90℃and60min respectively. When the amount ofPN-1was controlled in the range of50%to100%(on the weight of fabrics, owf), thegreat flammability of fabrics could be obtained, the limiting oxygen index was29%~32%,which showed that silk fabric was hard to ignite with a candle like fire. The tests of treatedsilk fabrics by IR spectra, SEM and XPS indicated that the flame retardant was graftedonto silk fabrics. Analysis of the XRD showed that the flame modification was onlyhappened in the amorphous region of silk. PN-1grafted silk fabrics have a little loss ofmoisture regain, air permeability and tensile strength, but these loss have little effect onwearability. After being subjected to15laundering cycles, the limiting oxygen index ofsilk fabric treated with PN-1was still above27%, which means the fabric has greatwashing durability.The other finishing system was compounding with organic phosphorus compound dimethyl methacryloyloxyethyl phosphate (DMMEP) and nitrogen compoundmethacrylamide (MAA). Then they were also grafted onto silk fabrics via copolymerizationmethod initiated by potassium persulfate. The optimal grafting technological parameterswere investigated by means of one-factor experiments. The influence of grafting yield andlimiting oxygen index by grafting order was studied, and the optimal ratio of the twochemical substances was also investigated. This experiment indicated that the silk fabric onlytreated by MAA showed no flame retardancy property. while compounded with DMMEP, itcould not only reduce the amount of DMMEP, but also promote the formation of charresidue which showed greater flame retardancy. When DMMEP and MAA were mixed inone bath on the weight ratio of1:1, which could get optimum synergistic flame retardancyeffect. The optimal grafting technological parameters were as follows: the pH value wasadjusted to3.5; the concentration of the initiator potassium persulfate (KPS) was1%(on theweight of monomer,owm); the liquor ratio was1:30; the reaction temperature increased to90℃and maintained at this temperature for60min. After being subjected to15launderingcycles, the limiting oxygen index of silk fabric treated with DMMEP and MAA was stillabove27.15%. IR spectra and XPS measurements of grafted silk fabrics showed that theflame retardant was successfully grafted onto silk fabric. Analysis of the XRD showed thatthe flame modification was only happened in the amorphous region of silk. The grafted silkfabrics have a little decrease of whiteness, moisture regain, air permeability and tensilestrength. But the wrinkle recovery angle increased, that could improve the fabric wrinkleresistance.