Study On The Flame Retardant Properties Of Environmentally Friendly Flame Retardants On LYOCELL Fibers And Cotton Fabrics

Firstly,in order to obtain eco-friendly green flame retardant cellulose fiber,natural biomass materials were employed to modify cellulose fibers.As a abundant,renewable,and eco-friendly bio-based compound,phytic acid(PA)possesses a high phosphorus content,and special molecular structure,which is potential for use as flame retardant of cellulosic fibers.Generally,PA is not efficient for cellulosic fibers because it displays strong acidic feature and greatly lowers mechanical properties and practical performance of the modified fiber.In the present paper,PA was firstly reacted with urea to synthesize a novel green flame retardant containing a high level of phosphorus and nitrogen elements,i.e.,phytic acid ammonium(PAA),and then it was applied to lyocell fibers through pad-dry-cure finishing process.As expected,the flame retardancy and durability of finished lyocell fibers were considerably improved.Secondly,PA can severe as a good flame retardant for cellulose fabrics,but PA’s strong acidic feature will weaken the mechanical properties of modified fibers.To solve this disadvantage,we try to exploit novel double coating method to obtain flame retardant cellulose fabrics.Egg protein,containing multiple amino acids with a high level of nitrogen element,is thus expected to combine phytic acid by intense clectrostatic attraction to flame retard celluloe fabrics.Based on the phosphorous-nitrogen synergistic flame retardant system,the macromolecular structure of egg protein can effciently protect the surface structure of fabrics from the damage by pure phytic acid.The cotton fabrics coated by pure egg protein show limited flame retardant.In contrast,the double coating for cotton fabrics with egg protein and phytic acid show excellent fire resistance for cotton.The surface morphology and micro-structure element composition of flame retardant cellulose fibers were studied by SEM,FTIR,and XPS.The thermal stability and combustion performance of cellulose fibcrs/fabrics were characterized by TG and vertical burning tests as well as limit oxygen index(LOI).All the results indicate that the lyoccll libers treated with PA A shows excellent fire resistance.The LOI of treated lyocell fibers is 30.5%even after 30 recycle washing cycles.The cotton fabrics coated by double egg protein and phytic acid also show high efficient flame retardancy.The heat ralease rate of modified cotton fabrica decreased from 171 w/g to 51 w/g.Based on these results,the mechanism of two flame retardancy systems were inferred by synergistic cooperation of gas phase and solid phase flame retardancy mechanisms.During the burning process of cellulose fibers,the flame retardant firstly tend to generate non-combustion gases.The non-combustion gases are favorable for diluting the concentration of combustible gases products in gas phase.At the same time,flame retardant catalyzes cellulose to dehydrate and carbonize in solid phase.Two functions significantly promote the forming of intumescent char layers and exhibit high efficient flame retardancy.