Optimized Preparation Process And Characterization Of Viscose Fiber Grafted Flame Retardant

Viscose fiber(VF)is a staple chemical fiber,which is made from wood or cotton short fleece by wet spinning.Viscose fiber is popular for excellent natural performance,but that application range is greatly limited by their inflammability.In this paper,cellulase was used to hydrolyze part of view?-1,4 glycosidic bonds on the surface of VF,and the exposed 1C hemiacetal hydroxyl group was oxidized to carboxyl group by glucose oxidase(GOD),carboxylized viscose fiber(CVF)was prepared finally.Then grafted melamine or guanylate on viscose fiber was synthesized,and the melamine with high contents of nitrogen and guanylate with nitrogen and phosphorus was used as flame retardant functional fragments,the N,N'-Dicyclohexylcarbodiimide(DCC)as a cross-linking agent.The optimization synthesizing process was studied systematically,and the infrared,staining,morphology,mechanics and thermal properties of the grafts sample were characterized in this paper.Finally,the relationship between flame retardant containing of viscose fiber and its limit oxygen index(LOI)was studied by method of blend squash technique,fitting function formulas and also.A rapid and precise method for evaluating the flame retardancy of flame retardant viscose fibers(FRVF)was established.The primary experimental results,conclusions and summarize is as follows:(1)Based on the single factor experiments,the orthogonal experiment of synthesizing CVF grafted melamine or guanylate was carried successively.The optimal process grafted melamine on CVF is that the mass ratio of DCC to CVF equal is 0.6,and the p H is 4.0,the temperature is 65?,reaction time is 2h in 50%ethanol.Finally nitrogen content of the grafted products is 3.19%.The optimal process graftd guanylate on CVF was the mass ratio of DCC and CVF is equal 0.6,the p H is 5.5,the temperature is 60?,reaction time is 4h in 50%ethanol,and the nitrogen content is 1.31%.(2)The results of infrared spectrum(IR)indicates that the new absorption peaks at900 and 1560cm^-1 belong to carboxylic acid,the new peaks at 2200cm^-1 belong to the amino group,and the enhanced peaks at 3500,1400 and 1000?1100cm^-1belong to the amide bond enhancement.It was indicated that viscose fiber grafted melamine(GMVF)and,viscose fiber(GGVF)grafted guanylate are synthesized successively through the infrared spectrum(IR).(3)The LOI value of GMVF and GGVF is successively 27.2 and 27.0,contrast with viscose fiber it is increased to 17.2%and 16.4%,separately.The total heat release(THR)is decreased to 0.228MJ/kg and 0.205MJ/kg,and the combustion time is prolonged to35.5%and 29.6%,respectively.The results of differential thermal analysis(DTA)indicates that GMVF and GGVF appear a weak endothermic peak in the temperature of300?,it is attribute to the endothermic decomposition of the C-N bond of melamine and guanylate,and the C=N bond is attribute to the melamine molecule.The GMVF and GGVF have the property of water-proof,and the correlation equation of resistance water and antiflaming.The equation is Y_GMVF=0.0005x²-0.025x+27,R²=1;Y_GGFV=0.0002x²-0.0117x+27.2,R²=1respectively,and in this equation Y represents to the LOI value,and the X represents to the content of nitrogen.(4)According to SEM analysis,GMVF has an average diameter of 14.643?m,which is 0.53?m larger than the viscose fiber and the average grafted thickness is0.265?m,The dry state strength is 3.17c N/tex and dry state elongation at break is28.66%;which is 0.55c N/tex and 4.39%higher than 2.62c N/tex and 24.27%;GGVF has an average diameter of 14.28?m,which is 0.176?m larger than the viscose fiber and the average graft thickness is 0.088?m;The dry state strength is 2.74c N/tex and dry state elongation at break is 25.13%,which is 0.12c N/tex and 0.86%higher than2.62c N/tex and 24.27%.(5)Up to 5%of the reductive terminal C1 hydroxyl on the viscose fiber surface is oxidized to a carboxyl group,which can be stably stained by electrostatic action with the positively charged basic fuchsin.Therefore,the amount of free carboxyl group of CVF can be determined by the change of concentration of basic fuchsin solution within a certain range.(6)The relation curves of content of nitrogen and LOI value of GMVF and GGVF are fitted respectively.The experimental results showes that the LOI value of the grafts flame retardant fiber increases with the increase of content of nitrogen in a certain range,and the correlation coefficient is more than 0.98.