Lignin/glucose-based Phosphorus Flame Retardant Blending Method To Modify Viscose Fiber

Viscose fiber is a kind of high quality regenerated cellulose fiber,which possesses smooth,cool,breathable,antistatic,and anti-ultraviolet properties.The raw material of viscose fibers,i.e.,cellulose,is abundant in nature sources.Viscose fibers and textiles are widely used in daily livings.However,the limiting oxygen index of viscose fibers is only 19%.Thus the inflammability of viscose fibers often causes fires,endangering people’s lives and property.Therefore,it is important to improve the flame retardancy of viscose fibers and further widen their wide applications in textiles in the textile field.In partⅠ,a novel compound containing phosphorus,nitrogen,and silicon flame retardant elements,lignin silane ammonium phosphate was synthesized by selecting lignin which holds a similar structure to cellulose and various functional groups.The flame retardant was verified by Nuclear magnetic resonance hydrogen spectroscopy and Fourier transform infrared spectrometer.The flame retardant viscose fibers were successfully obtained by blending with viscose solution with flame retardant and confirmed by Fourier transform infrared spectrometer and X-Ray photoelectron spectroscopy analyses.Thermal stability test results show that the char residue rate of flame-retardant viscose fibers（33.3%）are higher than that of untreated viscose fibers（12.8%）.It has excellent char residue（25.4%）after 50 washing cycles,and has outstanding thermal stability and durability properties.Scanning electron microscopy and Raman spectroscopy results show a dense expanded char layer was generated.It is mainly composed of condensed phase.The char layer is catalyzed to form char through lignin and acid sources,and helpful to enhance flame retardancy,prohibit heat and oxygen.In partⅡ,a new organic phosphine flame retardant diphenyl hypophosphonate glucose ester was designed and synthesized by the reaction of glucose and diphenylphosphinoyl chloride.Then flame retardant was added and dispersed in viscose solution,and the flame retardant viscose fibers were prepared by spinning.The molar ratio of solvent and reactants and the operation method of post-treatment were explored in detail.The flame retardant viscose fibers were prepared by blending the flame retardant with viscose solution.Relevant testing analyses prove that both flame retardant and flame retardant viscose fibers have been successfully prepared.Thermogravimetric analysis shows that the flame retardant can increases the char residue rate of the fibers（33.8%）,and it still maintain a certain char residue（22.3%）after 20 washing cycles.Micro-combustion calorimeter analysis shows that the maximum heat release rate of flame retardant viscose fibers after combustion（50W/g）are far lower than that of control viscose fibers（305 W/g）,indicating that the flame retardant can effectively inhibits the combustion of the fibers.The combined analyses of Thermogravimetric infrared and Thermogravimetric mass spectrometry indicate that the amount of CO₂and H₂O in non-combustible gases increased.Therefore,the mechanism of the flame retardant in the combustion process of the modified viscose fibers mainly belong to the gas phase flame retardant mechanism.