Improving The Flame Retardancy Of Cotton Fabrics By Introducing Soy Protein Isolates And Hydrolysates Through Finishing

Cotton fabric has many excellent properties such as biodegradability,moisture absorption and breathability,biocompatibility as a natural cellulose fabric,and thus has a wide range of applications in life and industry.However,its inherent flammability and thermal instability limit its application and development in various fields,which could cause fire hazard.Therefore,improving the flame retardancy of cotton fabrics has become an important issue in textile industry.For natural fibers,the flame retardancy has been mainly endowed by finishing treatments.In the experiment,environmentally friendly soybean protein isolate(SPI)and one amino acid(arginine)of SPI hydrolysate were introduced into the surface of cotton fabric,and the flame retardant mechanism was tested and analyzed.This paper mainly includes the main contents of three parts:In the first part,the cotton fabric was treated with the soy protein isolate(SPI)solution by dipping and rolling.The flammability,thermal stability,and char formation of the treated fabric were tested and evaluated by the limiting oxygen index(LOI),vertical burning test,scanning electron microscope(SEM)analysis and thermogravimetry analysis(TGA),muffle furnace,and cone calorimetry(CONE).The experimental results show that the treated fabric has the best flame retardancy when the concentration of SPI is 6%,the LOI of the fabric is increased about 1%,the char formation is significantly enhanced,and the amount of residue carbon is increased from 2.8%to 12.6%.The dimensional stability of the fabric after muffle furnace calcination is significantly improved,the SEM observation also indicates that the treated fiber remains more intact structure in the residue carbon.It is demonstrated that SPI on cotton fabrics mainly takes effect in the condensed phase during combustion.SPI forms a continuous film structure on the surface of cotton fibers,carbon is formed after heating to protect the fabric matrix by isolating the thermal oxygen,delaying the pyrolysis process of cotton fibers.In the second part,the fabrics was treated by padding with boric acid solution,followed by coating with SPI.The flammability of the cotton fabrics treated with the SPI/boric acid was investigated.First,the cotton fabric is treated in boric acid solution by a dipping and padding process,then,the SPI is dissolved in water to prepare a paste liquid before being introduced into the surface of the fabric by coating.It is proved that the fabric sample treated with 10%boric acid solution and coated on one side with protein has optimal flame retardancy.The LOI was increased from 17.4%to 33.6%,and the damage length was reduced from 30.0 cm to 8.0 cm in the vertical burning test.Besides,the amount of carbon residue increased significantly.In the third part,the effect of arginine,which is one of the hydrolysates of soybean protein isolate,on the flame retardancy of cotton fabrics was studied.The arginine/borax blend system and the Arginine/Dimethyl methylphosphonate(DMMP)complex system were incorporated into the fabric by dipping and padding.The arginine/borax treatment increased the LOI of the cotton fabric from 17.4%to 24.9%,the addition of borax caused smoldering,while the introduction of arginine reduced the smoldering time from 303 s to 145 s,and reduced the damage length from 14.0 cm to 4.9 cm.The arginine/DMMP combination also significantly improved the flame retardancy of the fabric.It is suggested the arginine can increase the wettability of DMMP to cotton fabrics,thereby increasing the add-on amount of DMMP to cotton fabrics,and hence provide a better flame retardancy to cotton.The weight gain of the fabric treated with the solution containing 18%DMMP and 8%arginine was significantly higher than that treated with the solution containing 26%DMMP.The LOI was increased to 26.4%,the damage length in vertical burning test was reduced from 30.0 cm to 12.3 cm,and the char formation was enhanced.