In Situ Construction Of Composite Coatings To Achieve Flame Retardancy And Multi-functionalization Of Cotton Fabrics

Cotton fabrics are a kind of natural textile with the largest consumption and are widely used in apparel,flexible packaging and interior materials for their excellent comfort and air permeability.However,they are easy to be ignited and become the carrier for the propagation of flame due to their inherent chemical structure.The introduction of flame retardants（FRs）will reduce the fire risk of cotton fabrics,but many kinds of FRs will bring smoke hazards,health and environmental risks.Therefore,the design of safe and eco-friendly flame-retardant cotton fabric is imperative.In addition,with the development of the technology,the demand for multifunctional flame-retardant cotton fabrics is increasing.Therefore,the investigation on multifunctional cotton textiles has great significance both in theory and practice.This work has focused on the development of safe and eco-friendly multi-functional flame-retardant cotton fabrics.Supramolecular aggregates,one-dimensional phosphorus-nitrogen complexes,two-dimensional layered double metal hydroxides（LDH）and bio-based aerogel were respectively introduced on the surface of cotton fabric by in situ preparation.The problems caused by the introduction of flame retardants,such as the increased smoke generation,the advanced ignition time,and so on,were solved through the structural design of the flame retardant system.The flammability,mechanical properties,superhydrophobicity,anti-bacterial ability and electromagnetic shield were characterized.The flame retardant mechanism of the corresponding coatings was discussed and proposed.1.A novel gas source AM was synthesized by melamine and p-aminobenzenesulfonic acid,and a high efficiency intumescent flame retardant coating AM-chitosan（CS）/ammonium polyphosphate（APP）was constructed on the surface of cotton fabrics by layer by layer self-assembly.APP and AM spontaneously formed supramolecular aggregates in situ during assembly,which improved the bonding force between layers and maintained the mechanical properties and softness of the fabrics.After flame retardant treatment,the limiting oxygen index（LOI）of cotton fabrics reached 31.5,and the damage length was 4.3 cm.Compared with untreated samples,the peak heat release rate（p HRR）and total heat release（THR）decreased by 39.2%and 59.9%,respectively.AM generated more non-combustible gases during combustion,resulting in the formation of more expanded carbonaceous structures.To evaluate the effect of APP and AM on cell proliferation,AM showed lower cytotoxicity at the same dose.Compared with CS/APP flame retardant system,this coating showed higher flame retardant efficiency,better softness and higher safety factor.2.A kind of zinc-based nitrogen phosphorus complexes（Zn PN）was prepared by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide,dimethyl-imidazole and Zn Cl₂.Zn PN in situ grew on the cotton fabrics by the chelation between dopamine（PDA）and metals,and the fabrics were further coated with polydimethylsiloxane（PDMS）to obtain flame-retardant,superhydrophobic and antibacterial cotton fabrics.The results showed that the LOI value of the modified cotton fabric was increased to 23.6,the p HRR and THR decreased by 28.0%and 23.7%,respectively,and the total smoke production（TSP）decreased by 34.8%.Since Zn PN formed a one-dimensional"needle-like"arrangement on the surface of cotton fabrics,which constituted a rough surface,and combined with PDMS to impart superhydrophobic properties to cotton fabrics,resulting in the water contact angle（WCA）of the fabrics reached 161°.In addition,the superhydrophobic coating effectively improved the flame retardant durability and anti-bacterial adhesion of the fabric effectively.3.A single-layer directional growth two-dimensional LDH coating was constructed on the surface of cotton fabric by the bridge effect of PDA,which effectively solved the problems of agglomeration and weak bonding of LDH nanosheets on the surface of fabric,and improved the flame retardancy and suppressed the smoke release of fabrics.The flammability characterization showed that,compared with that of the untreated cotton fabrics,the p HRR and THR of the treated fabrics decreased by 38.2%and15.9%,respectively,and the total smoke release（TSR）decreased by 98%,and the toxicity of the released smoke also decreased.The analysis of char residue and smoke particles confirmed that,on the one hand,LDH played a catalytic role to reduce the release of the smoke,and on the other hand,the rough structure acted as a"multi path barrier",reducing the smoke release.The cotton fabrics were endowed with stable superhydrophobicity by the combination of PDMS.The durability of the coating was improved,which had a great potential to be applied in the field of oil-water separation.4.A flame-retardant cotton fabric which can filtrate particulate matter（PM）was prepared by thermal stable inorganic LDH with high specific surface area,the phytic acid（PA）,and the Fe³⁺organic complex.The LOI value of the treated fabrics reached 33.9,the damaged length was 6.3 cm,and the THR decreased by 78.2%.The early decomposition of Fe³⁺PA promoted the formation of carbon cross-linked network in the condensed phase.LDH enhanced the oxidation resistance of the char layer,and the metal salts formed at high temperature improved the thermal stability of the char layer.The introduction of LDH further enhanced the inhibition effect of the self-assembled layer of PA and Fe³⁺on smoke toxicity.Moreover,the TSP was decreased by 51.0%,and the release of CO caused by Fe³⁺PA was inhibited in a rate of 47.7%.In addition,the adsorption and filtration performance of the treated cotton fabrics to PM was improved by 13%compared with that of the untreated fabrics,and long-term filtration could be achieved.5.A cotton aerogel interpenetrating network was obstain by in situ construction of calcium-zirconium double-ion crosslinked sodium alginate（SA）aerogels with cotton fabrics as a skeleton structure.Silver nanowires（Ag NWs）were introduced into the middle layer to obstain a tertiary structure with external thermal insulation and internal thermal conductivity.Meanwhile,a cotton fabric labeled as C-Ag-SA（Ca/Zr）with flame retardant,hydrophobic,antibacterial and electromagnetic shielding functions was obtained.The results showed that the LOI value of C-Ag-SA（Ca/Zr）reached31.5.Compared with that of the control cotton fabrics,the p HRR decreased by 37.1%and the ignition time was delayed by 34 s.The design of"transverse heat conduction and longitudinal heat insulation"was achieved to reduce the fire risk of flame retardant coating.In addition,the electromagnetic shielding effectiveness（SE_T）of C-Ag-SA（Ca/Zr）was 56.3d B,which was increased 37.0 d B compared with that of the fabrics samples deposited with Ag NWs but without SA.Moreover,due to the hydrophobic characteristics caused by Zr²⁺crosslinking treatment and the adhesion of SA,the SE_Tof C-Ag-SA（CA/Zr）still reached 44.4 d B after 12 h water washing cycle.In terms of antibacterial properties,Zr²⁺and Ag NWs played a synergistic role,showing a good antibacterial ability.This work has a great commercialized potential in the field of special protective scenarios.