Study On Flame-retardant Modification Of Lyocell Fiber By Surface Grafting

As a comfortable,breathable and biodegradable green environmental friendly fiber,Lyocell fiber possesses excellent wet and dry strength,outstanding mechanical and chemical treatment resistance,low energy consumption and pollution-free production process,and has been widely used in people's daily life.At the same time,as the raw material of Lyocell fiber,natural cellulose can be found widely in nature and has abundant reserves.However,due to the flammability of Lyocell fibers,it has become a major safety hazard in life and production.Therefore,to improve the flame retardancy of Lyocell fiber is of great significance for its application.In this paper,two kinds of grafting methods were used to modify Lyocell fibers,and the corresponding flame retardant fibers were prepared.The structure and nature of samples before and after modification were studied in detail,and the flame retardant mechanism was analyzed and discussed.In the first part of this paper,the sorbitol-based flame retardant was designed and synthesized.The Lyocell fibers were treated by sorbitol-based flame retardant.Sorbitol-based phosphorus-nitrogen flame retardant was prepared by reaction of sorbitol with phosphoric acid and urea.The fire retardant and durable Lyocell fibers were prepared by dipping-drying and curing.The preparation process of the flame retardant is simple and does not produce harmful substances such as formaldehyde and so on.In the process of treating cellulose fibers,only water is used as solvent,and the conditions are mild,safe and environmentally friendly.Fourier transform infrared spectroscopy(FTIR)characterization show that the sorbitol-based flame retardant is successfully synthesized and applied to the durable flame retardant finishing of Lyocell fibers.Scanning electron microscopy(SEM)images show that the surface morphology of the fibers remain unchanged after the flame retardant finishing,and the finishing process has no effect on the surface of the fibers.Thermogravimetric(TG)analyses show that the content of the residual carbon increase by 26%after the flame retardant treatment and 20 times of washing.It still has good flame retardant durability.In the second part,phosphorus-nitrogen synergistic flame retardant Lyocell fibers were prepared by two-step method.First,acrylamide was grafted onto regenerated cellulose fibers,and then the fibers were phosphorylated by flame-retardant functional monomers.The method has a wide range of applications and can be extended to prepare flame retardant Lyocell fibers by chemical reaction of various flame retardants with polyacrylamide.Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy(XPS)analyses show that the flame retardant elements are successfully bonded to the surface of the fibers.Thermogravimetric analyses and scanning electron microscopy show that the flame retardant treated fibers has good charring properties.Based on the results of Pyrolysis-Gas Mass Spectrometry,the flame retardant mechanism of the flame retardant treated fibers is mainly based on condensed phase flame retardant mechanism,which has gas flame retardant effect as well.