Synthesis Of Polyphosphate Flame Retardant PPAP And Study Of Its Application On Cotton Fabrics

With excellent mechanical properties, anti-static, good moisture permeability performance, comfortable wearing, wide variety of sources and so on, cotton fabric is widely used as technical textiles and garment textiles. However, cotton fabrics are flammable fabrics. The LOI of 100% cotton fabrics is only 18. The potential flammability limits its application in some areas. Therefore, study and reaearch new effective flame retardant systems for cotton to improve flame resistance had became the hotpoint.The current flame retardants for cotton fabrics are mainly nitrogen, phosphorus-based, which have excellent flame retardancy and release less toxic gases and smoke. The flame retardants with nitrogen and phosphorous containing in the same molecule show higher flame retardant efficiency, and firmer carbon layer due to phosphorus-nitrogen (P-N) synergism phenomena, and become the mainstream for developing new flame retardants for cotton.In this paper, a novel oligomric phosphoramide flame retardant poly(phenyl-O-(2-aminoethyl) phosphonamidoate) (PPAP) was synthesized from phenyl dichlorophosphate (PDCP) and ethylenediamine (EDA) and characterized by fourier transform infrared spectrometry (FT-IR),1H nuclear magnetic resonances (1H NMR). Number average degree of polymerization and number average molecular weight of PPAP were determined by analyzing the number of primary amino groups at the two ends of the molecular chain. Application of PPAP on cotton fabric was also studied. In this paper, in order to studied the flame retardant mechanism of PPAP on cotton fabric, we compared the flame retardant effect of the two similar compounds PPAP and poly(2-hydroxyethyl) phenyl phosphate (PHPP) which containing one flame retardant element phosphorous only. The work of this paper was done as follows:(1) Synthesis of PPAP which was characterized by FT-IR, 1H NMR. Through single-factor experiments, the best synthesis conditions were summarized as follows:The best molar ratio of PDCP and EDA was 1:1.3, the reaction temperature was 55-60℃, the dosage of molar of deacid reagent triethylamine was 1.12 times as PDCP, the dosage of solvent chloroform was three times as the volume amount of PDCP. At these conditions, the number-average degree of polymerization and molecular weight of synthesized product were 2.47 and 551.04 respectively which were determined by terminal group analysis.(2) Using resin DM508 as cross-linker and dipping-drying process to treat the PPAP on cotton fabrics. The best finishing conditions were determined by single-factor experiments and the results were as follows:the best dosage of PPAP and DM508 were 350 g/L and 100 g/L respectively, the best dosage of catalyst H3PO4 was 25 g/L, curing at 160℃for 3 min. At these conditions, the treated cotton fabric was tested with 0 s of after-flame time,0 s of after-glow time, 9.8 cm of char length and 29.9 of LOI. However, the FR fabrics could not be subjected to normal home laundering.(3) Another flame retardant PHPP which had the similar chemical structure as PPAP was prepared to assiste to study the flame retardant mechanism of PPAP on cotton fabric by comparative analysis. By comparing the flame retardant effect of PHPP on cotton, the solid phase mechanism and interrupt heat mechanism of PPAP on cotton was went into detail. By comparing the different thermogravimetric analysis (TGA) curves of the fabrics treated with PHPP and PPAP respectively, the mechanism of flame retardant was futher explained as follows:The decomposition temperature range of PPAP was 217-291℃which was started by rupturing of P-N-C bond at 217℃. The decomposition process of PPAP changed the course of pyrolysis of cotton fiber, promoted carbonization of cotton, inhibited combustion. However, the carbonization of cotton was main derived from the effect of phosphorus, rather than nitrogen, the nitrogen had no catalyst effect in carbonization process.In a conclusion, the P-N synergistic FR PPAP is effective for cotton fabrics and could be used as a market-potential non-durable flame retardant agent for cotton fabrics.