| Various fabrics using cotton fiber as the main raw material often have the advantages of moisture absorption and warmth,good breathability,and durability.Therefore,cotton fabrics have been widely used in various human activities and daily life.However,the widespread use of cotton fabrics has also brought huge fire hazards,because cotton fabrics are extremely flammable,which also limits the application of cotton fabrics.Therefore,it has become the pursuit of many researchers to modify the cotton fabric to change it from flammable to non-flammable.Up to now,people have developed a wide variety of flame retardants(FR),such as halogen-containing flame retardants,inorganic flame retardants,organic phosphorus-nitrogen flame retardants and so on.Although the halogen-containing flame retardant can play a good flame retardant effect,it will release toxic substances to poison the human body,corrode equipment and pollute the environment,so it has been strictly prohibited;inorganic flame retardants include metal oxides and hydroxides,inorganic Silicon-containing compounds,red phosphorus,expandable graphite,etc.,their use is mainly doped and filled directly into the base material.They can improve the fire resistance of the base material while inhibiting the generation of smoke,and is non-toxic and non-corrosive.However,due to the large amount,it will affect the mechanical properties of the base material.In contrast,organic phosphorus-nitrogen flame retardants have been widely studied and applied in recent years,because organic phosphorus-nitrogen flame retardants are usually connected through chemical reactions.It is branched onto the substrate,the amount is small,and the effect is good.Research shows that due to the synergistic effect of phosphorus and nitrogen flame retardant elements,it will be more effective than a single flame retardant element.Not only can it significantly reduce the thermal degradation temperature of the base material,but it also has low toxicity,high efficiency,and durable flame retardant effects.Therefore,it is of great significance to deeply study organic phosphorus-nitrogen flame retardants and introduce more flame retardant elements to exert their synergistic effect.In this paper,three new multi-element synergistic flame retardants for cotton fabrics are designed,synthesized and applied.The synthesis process is relatively simple,the cost is low and the flame retardant efficiency is high.(1)Synthesis of flame retardant pentamethylene ammonium phosphate guanidazole(AGPMPA)and its application on cotton fabrics.After synthesizing guanidazole from hydrazine hydrate and dicyandiamide,a new type of phosphorus-nitrogen flame retardant pentamethylenephosphonium ammonium guanidazole(AGPMPA)was synthesized by using its active hydrogen to react with formaldehyde and phosphorous acid,and verified its structure with NMR.Fourier transform Infrared spectroscopy(FT-IR)showed that AGPMPA formed P-O-C bonds with cotton fabrics after flame retardant finishing.The Limiting Oxygen Index(LOI)and durability tests show that 20%AGPMPA can increase the LOI value of cotton fabrics from 18.6%to 43.7%,and still maintain 26.8%after 50 washings.During the vertical combustion test,it was found that the treated cotton could not be ignited,and a significant carbon frame was left at the ignition.Thermogravimetric(TG)analysis shows that the thermal stability of cotton fabrics is significantly improved after flame retardant finishing.Thermogravimetric-infrared(TG-IR)tests show that compared to raw cotton,the amount of volatile products produced by degradation of the treated cotton is significantly reduced,and the heat release rate(HRR)and total heat release(THR)are significantly reduced,meaning Combustion agents can play a role in both the solidified phase and volatility.Scanning electron microscopy(SEM)observations showed that the fiber structure of the cotton fabric did not change significantly before and after the flame retardant treatment.The mechanical strength of cotton fabrics decreased after flame retardant finishing,but to a lesser extent.(2)Synthesis of P-N-Si Synergistic Flame Retardant HPAPA and Its application on cotton fabricsFrom aminopropyltriethoxysilane,phosphorus pentachloride,ethanolamine,phosphoric acid,etc.,a high-efficiency flame retardant rich in three flame retardant elements P,N and Si,was synthesized.The chemical structure of the flame retardant was verified using NMR.Fourier transform Infrared spectroscopy(FT-IR)and elemental analysis(EDS)results showed that the fiber was successfully grafted onto the surface of cotton fabric.After treated with 30%P-N-Si FR,the LOI of cotton fabrics was increased from 18.2%to 52.0%,and after washing 50 times,it could still remain at 27.9%.TG analysis show that compared with raw cotton,the degradation temperature of cotton fabrics after flame retardant treatment is significantly reduced,and the residue rate is greatly increased,indicating that the degradation degree of cotton fabrics is reduced and the thermal degradation stability is improved.TG-IR analysis also confirmed that the THR,HRR and EHC values of treated cotton were significantly lower than those of raw cotton.Observated by SEM revealed that the flame retardant had no significant effect on the main structure of cotton fibers.The mechanical properties of cotton fabrics have not changed much.(3)Synthesis of P-N-S Synergistic Flame Retardant(FR)DAPEPPAP and its application on Cotton FabricsA new polythiourea-phosphoric acid type flame retardant rich in phosphorus,nitrogen and sulfur elements was synthesized from thiourea,phosphoric acid,ethanolamine,and phosphorus pentachloride as main raw materials,and was successfully applied to cotton fabrics.Infrared spectroscopy and elemental analysis confirmed the presence of phosphorus,nitrogen,and sulfur in flame-retardant cotton.The SEM images proves that the introduction of flame retardants had hardly affect on the structure of cotton fibers.The TG results confirmed that the degradation temperature of the treated cotton was reduced by 72°C compared with the raw cotton under nitrogen atmosphere,and the degradation degree was weakened,and the residue rate was significantly increased from15.57 to 49.06%.TG-IR results showed that the mean-HRR of raw cotton decreased from9.20 kW/m~2 to 4.83 kW/m~2 and the THR decreased from 2.83 MJ/m~2 to 1.45 MJ/m~2.Experimental results show that 30%of the flame retardant can endow cotton fabrics excellent flame retardancyand durability.In addition,the mechanical performance test shows that the flame retardant has little effect on the strength of cotton fibers. |
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