The Preparation,Properties And Flame-Retardant Mechanism Of Flame Retardant Cotton Fabric Based On Biomass Materials

As a kind of natural fibers,cotton fibers have a long history of application in human production and life.Because the cotton fabrics have the advantages of heat preservation,moisture absorption,air permeability,and heat preservation,they are suitable for different fields.Therefore,cotton fabrics have been applied in different fields.However,the LOI value of cotton fabrics is about 18%,which means cotton fabrics belong to the flammable material.The flammability of cotton fabrics might bring us serious casualties and incalculable property loss.Therefore,the enhancement of flame retardancy for cotton fabrics is significant.?1?The flame-retardant cotton fabrics were prepared by Layer-by-Layer assembly?LbL?technology using lignosulfonate?LS?and chitosan?CS?.The flame-retardant cotton fabrics were named as LS/cotton-17.1 wt%,CS/LS/cotton-17.0 wt%and CS/LS/cotton-25.2 wt%,respectively.Vertical flame test?VFT?,cone calorimeter test?CCT?,scanning electron microscope equipped with energy dispersive spectrometer?SEM-EDS?,thermogravimetric analysis along with Fourier transform infrared analysis?TG-FTIR?,and limiting oxygen index?LOI?were utilized to explore the flame retardancy,thermal degradation properties,and flame-retardant mechanism of samples.The results of Fourier transform infrared analysis coupled with an attenuated total reflection?ATR-FTIR?and SEM showed that the flame retardants were successfully deposited on the surface of cotton fabrics,and formed uniform films.The LOI values of the flame-retardant cotton fabrics were 24.7%,25.0%,and 26.0%respectively,and the afterflame times of them decreased.However,in the VFT,the flame-retardant cotton fabrics presented afterglow phenomenon.With the increase in the amount of CS,the values of afterglow time decreased.The SEM pictures of char residues after the VFT showed that CS and LS formed an intumescent flame-retardant system,and the structure of cotton fibers still remained intact.The results of TGA indicated that the deposition of CS/LS significantly reduced the R_max value of cotton fabrics and a number of char residues formed at 700 ^oC were higher than that of cotton fabrics,whatever in nitrogen or air atmosphere.This phenomenon proves that flame-retardant cotton fabrics have great thermal stability at a higher temperature zone.Moreover,the heat release rate?HRR?and total heat release?THR?values of flame-retardant cotton fabrics were lower than these of cotton fabrics,and flame-retardant cotton fabrics have good smoke suppression performance.TG-FTIR results showed that the flame-retardant cotton fabrics release more nonflammable gases and less flammable gases in the thermal degradation process.Thus,the flame-retardant cotton fabrics prepared by CS and LS obtained great flame-retardant properties.However,the whiteness of cotton fabrics was reduced,which might influence the utilization of flame-retardant cotton fabrics.?2?Ammonium phytate?AP?was prepared by phytic acid?PA?and ammonia water and it was utilized as the anion component to prepare flame-retardant cotton fabrics with CS through the LbL technology.XPS,tensile strength test and antibacterial rate test were also used to test the samples.The SEM pictures presented that there were obvious films on the surface of CS/cotton and CS/AP/cotton,which connected the adjacent cotton fibers.ATR-FTIR results presented that the flame-retardant coating was deposited on the surface of cotton fabrics successfully.LOI values of flame-retardant cotton fabrics increased significantly,the LOI values of AP/cotton and CS/AP/cotton were 29.0%and 27.0%,respectively.AP/cotton and CS/AP/cotton achieved self-extinguish as well as 0 s afterflame and afterglow time in the VFT,and the damaged length of AP/cotton was reduced to 73 mm.The HRR and THR of flame retardant cotton fabrics were lower than these of cotton fabrics,but the total smoke production?TSP?of AP/cotton increased.However,the TSP value of CS/AP/cotton decreased after the addition of CS.The results of TG in nitrogen atmosphere presented that the flame-retardant cotton fabrics retained more char residues at a higher temperature zone;the flammable substances?C-O-C,C=O,and C-H,etc.?produced by the flame-retardant cotton fabrics decreased,and the nonflammable gases?H₂O and CO₂,etc.?were higher than these of the cotton fabrics in the thermal degradation process.At the same time,the flame-retardant cotton fabrics can release NH₃,which can dilute the concentration of O₂.AP formed phosphoric acid and/or polyphosphoric acid during combustion process,which can promote the dehydration and carbonization of cellulose into char residues,preventing or delaying the flame spread.Moreover,the tensile strength of AP/cotton reduced,while the addition of CS improved the tensile strength of CS/AP/cotton.At the same time,the existence of CS enhanced the antibacterial performance of flame-retardant cotton fabrics.The flame-retardant cotton fabrics obtained both excellent flame-retardant and antibacterial properties.?3?3-piperazine-propyl-methyl-dimethoxysilane?GP-108?and PA were utilized to prepare GPA,then it was used to prepare flame-retardant cotton fabrics through dip-coating method.In order to make sure the best conditions of the flame-retardant cotton fabric preparations,different pH values,GP-108 concentration and soaking time were studied.The best conditions were determined as follows:the concentration of GP-108was 5 wt%,pH=4.5 and the soaking time was 5 min.The coating structure,combustion behaviors,thermal stability,and flame-retardant properties and flame-retardant mechanism of control,FR cotton-1?9.35 wt%weight gain rate?,FR cotton-2?12.74 wt%weight gain rate?and FR cotton-3?14.33 wt%weight gain rate?were characterized by SEM-EDS,ATR-FTIR,LOI,VFT,TG-FTIR,and CCT.SEM pictures depicted that the cotton fiber surface adhered to films,and the structure was complete after treatment.FTIR results showed that there were new peaks appearing in the FTIR spectra of flame-retardant cotton fabrics,and this proved that GPA had been successfully deposited on the surface of cotton fabric.The results of the VFT showed that with the increase of flame-retardants,the damaged length of cotton fabric decreased gradually,and FR cotton-3 had the lowest damaged length,which was 11.0 cm.The LOI values showed the same trend as the VFT,and the maximum value of FR cotton-3 was 29.0%.The results of CCT presented that the HRR and THR values of flame-retardant cotton fabrics were much lower than these of cotton fabrics.TG-FTIR results indicated that the char residues of flame-retardant cotton fabrics were higher than these of control at a higher temperature zone,and more nonflammable gases?NH₃ and H₂O,etc.?were produced during the thermal degradation.The SEM-EDS results of FR cotton-3 and its char residues showed that the sample formed stable char residues,which prevented further combustion of cotton fabrics.The above results explored that the flame-retardant cotton fabrics have the flame-retardant mechanism of gas phase and condensed phase.However,due to the weak acidity of the solution,the tensile strength of cotton fabrics was slightly reduced.