Preparation And Properties Of Flame Retardant Cellulose Fibers

Lyocell fiber,as a new type of regenerated cellulose fiber,overcomes the shortcomings of viscose fiber that will cause pollution to the ecological environment in the production process.In addition,the fiber has the advantages of environmental protection,natural degradation,good biocompatibility and wearability,which is known as the green fiber in the 21st century.However,lyocell fiber is easy to cause fire and bring great harm to the safety of human life and property.Therefore,it is of great significance to improve the safety and expand the application range of lyocell fiber by flame retardant modification.In this paper,based on the structure and intrinsic flame retardant properties of sodium alginate,two efficient flame retardant cellulose fibers with structure similar to sodium alginate were designed and prepared by chemical grafting and oxidation,respectively.X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR),thermogravimetry(TG),combustion test,microscale combustion calorimetry(MCC),scanning electron microscopy(SEM),Raman spectroscopy(Raman),thermogravimetric-infrared(TG-IR),pyrolysis gas chromatography-mass spectrometry(Py-GC/MS),single-fiber strength test were used to characterize and analyze the structure,properties and flame retardant mechanism of the two kinds of flame retardant cellulose fibers.In the first part of this paper,carboxymethylated lyocell fibers were prepared by etherification reaction between sodium chloroacetate and hydroxyl groups in the structure units of lyocell fibers.Due to the introduction of a large number of sodium carboxylate groups(–COONa),the fibers were very soluble in water,so the water solubility of the fibers was solved by chelation with aluminum ions.Finally,a kind of high efficient and nontoxic flame-retardant cellulose fibers were prepared.The results show that the modified fibers have excellent thermal stability and flame retardancy.In a nitrogen atmosphere,the char residue of the modified fibers increased from 15.1 wt%of the unmodified fibers to 31.8 wt%at 800 ^oC,and the peak heat release rate(PHRR)and total heat release(THR)decreased by 77.4%and 76.3%,respectively.In addition,the tensile strength of the modified fibers decreased from 3.95 c N/dtex of the unmodified fibers to 3.08 c N/dtex,retaining good mechanical properties.In the second part of the thesis,the 2,2,6,6-Tetramethylpiperidinooxy(TEMPO)/Na Cl O₂/Na Cl O oxidation system was used to oxidize lyocell fibers,and then the primary hydroxyl groups on the cellulose structural units were successfully oxidized to carboxyl groups to obtain oxidized fibers.Finally,the flame-retardant cellulose fibers were obtained by chelation with aluminum ions.The results show that the modified fibers have good thermal stability,char formation and flame retardancy.In a nitrogen atmosphere,the char residue of the modified fibers increased from 15.1 wt%of the control fibers to 33.3 wt%at 800 ^oC,and the PHRR and THR decreased by 79%and 43.5%,respectively.In addition,compared with the blank sample,the tensile strength of the modified fibers decreased by only 19%,from 3.95 c N/dtex to 3.20c N/dtex.