Study On The Flame Retardant Performance Of Multi-reactive Group Containing-phosphorus Flame Retardant On Cotton

Cotton fabrics are widely used in clothing,home furnishings,automobile and other applications because of its good comfort,hygroscopicity,biodegradability and affinity to human skin.However,cotton fiber is a flammable fiber,which has potential risk to human life and property.In order to improve the flame-retardant properties of cotton fabrics,people have made a lot of efforts.Various synthetic chemical materials have been used to improve the flame retardant properties and durability,such as:Pyrovatex CP^?and Proban^?.But these traditional flame retardant finished cotton fabrics will release harmful gases(formaldehyde)during usage,which are harmful to human health.Halogen flame retardants can give cotton fabrics good flame-retardant properties,are gradually banned due to the negative impact of halogen compounds on the environment.With the depletion of global petroleum resources and people's increasing awareness of human health and environmental protection,people are gradually turning their attention to biomass materials such as DNA,protein,amino acids,phytic acid and whey protein.These biomass materials are safe,renewable,environmentally friendly and other characteristics,therefore is considered to have great potential in the field of flame retardant.In this paper,three kinds of flame retardants for cotton are designed and developedrespectivelybasedonbis(2-hydroxyethyl)imino tris-(hydroxymethyl)-methane(BIS-TRIS),L-citrulline and L-methionine.Among them,the flame retardant ABTMPA is a halogen-free,formaldehyde-free,phosphorus-containing durable flame retardant;ACPMPA is a P-N synergistic flame retardant and durable flame retardant based on biomass;methionine-based FR is a biomass-based,containing P/N/S flame retardant elements and durable flame retardant.The synthesis of three flame retardants,the characterization of the structural,the flame retardant finishing,the analysis of the flame retardant properties of the finished fabric,and the structure characterization of the flame retardant fabric are studied.The main research results are as follows:(1)A novel flame retardant with high P content and ammonium polyphosphate active groups was synthesized,namely bis(2-hydroxyethyl)imino tris-(hydroxymethyl)-methane(BIS-TRIS)methylphosphonic acid(ABTMPA).The structure of the ABTMPA was analyzed by the nuclear magnetic resonance(NMR).The ABTMPA treated cotton fabrics were characterized by scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and fourier transform infrared spectroscopy(FTIR).The results showed that limit oxygen index(LOI)value of cotton fabric treated with 21%,26%and 31%ABTMPA were 40.8%,46%and 50.2%,respectively;after 50 laundering cycles,the LOI values were 29.0%,36.2%and 41.2%,respectively.The finished fabrics had good durability because ABTMPA and the cotton fabrics form phosphonate and carboxylate covalent bond.Micro calorimetric(MCC)showed that total heat of combustion(THC)of the treated cotton fabrics were reduced,and the char residual was much higher than that of pure cotton.Thermogravimetric(TG)and TG-FTIR analyses indicated that the flame retardant ABTMPA changed the thermal decomposition pathway of cellulose,and the combustible gases generated at high temperature was much lower than that of pure cotton.Flame retardant treated cotton fabric had excellent flame retardancy and durability.In addition,whiteness and breaking strength of treated cotton are well maintained.Therefore,ABTMPA has a good application prospect.(2)L-citrulline is a biological extract.A novel flame retardant(FR),ammonium salt of citrulline-penta(methylphosphonic acid)(ACPMPA)based on L-citrulline was synthesized,and its structure was characterized by ¹³C,¹H and ³¹P nuclear magnetic resonance(NMR)spectroscopies.The ACPMPA flame retardant molecule contains five ammonium salts of phosphorus acid and one ammonium salt of carboxylic acid,which allowed the covalent attachment of ACPMPA into cellulose via-P=O(-O-C)and–COOC bonds.The results testified that the treated cotton fabrics had very high flame retardance and excellent durability.The limit oxygen index(LOI)of cotton fabrics treated with 25%,30%and 35%-ACPMPA were 37.8%,47.0%and 49.2%,respectively;After 50 LCs,the LOI values were 31.8%,33%and 34.2%.Vertical flame tests also demonstrated that the treated cotton fabric acquires good flame retardance.The thermogravimetry(TG)and TG-IR results showed that the treated cotton left more residues and released almost no flammable volatiles at high temperature.Cone calorimetry results detected that the treated cotton released less heat than the pure cotton.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)results characterized that the flame retardant molecules entered the fiber and the structure of the finished cotton fabric is almost unchanged.The formaldehyde content of the treated cotton was measured,the test result of free formaldehyde in the treated cotton was"not detected",indicating that the treated cotton was safe and reliable.The treated cotton fabrics also retained good tensile strength and whiteness.(3)A novel reactive flame retardant(methionine-based FR)for cotton containing P,N and S flame retardant elements with methionine as raw material was synthesized to investigate the synergism of P/N/S flame retardant elements.The cotton fabrics finished with methionine-based FR had good flame retardancy and durability.The limit oxygen index(LOI)of cotton fabrics treated with 19%,24%,and29%-methionine-based FR were 39.4%,41.5%and 43.9%,respectively;After 50laundering cycles,the LOIs were 31.5%.35.1%and 37.7%.Thermogravimetry(TG)and thermogravimetry coupled with Fourier transform infrared spectroscopy(TG-FTIR)tests showed that the flame retardant(FR)changed the cellulose decomposition pathway so that a large amount of residue was formed and only a small amount of combustible gases was generated.Scanning electron microscopy(SEM)showed that the treated fibers were swollen,implying that the FR molecules entered the interior of the fibers,while X-ray diffraction results suggested that the FR have little effect on the cellulose structure.FTIR and X-ray photoelectron spectroscopy(XPS)results demonstrated that the methionine-based FR contains P,N and S elements,and has a P/N/S synergistic flame retardant effect,the FR and cellulose formed stable P(=O)-O-C and-COOC-covalent bonds,while microscale combustion calorimetry(MCC)experiments showed that the total heat release of the treated cotton fibers decreased considerably and the tensile strength of the finished cotton fabrics decreased slightly relative to those of the raw cotton.The free formaldehyde content of the treated cotton was tested,and the results showed that no free formaldehyde was detected in the treated cotton.