Preparation And Properties Of Durable Flame Retardant Wool Fabrics With Low Smoke And Toxicity

As a natural textile material,wool is often used to make high-end clothing and household items.Wool fabrics contain high nitrogen,sulfur,and moisture contents,which makes them have a certain flame retardancy performance(LOI value=24-26%).However,for many areas with high standard requirements,such as seats,carpets,etc.in high-speed train,the flame retardant performance of wool fabrics is not enough.Therefore,it is necessary to conduct further flame retardant finishing of wool fabrics to expand its application fields.In this context,phosphorus-containing flame retardant systems and different metal salt solutions were used as flame retardant finishing agents to fabricate efficient and durable flame retardant wool fabrics.The main research contents are as follows:(1)A phosphoramide flame retardant(dimethyl N,N-bis(2hydroxyletheylphosphoramidate),DMBHP)and crosslinking agent(1,2,3,4butanetetracarboxylic acid,BTCA)were combined to impart durable flame-retardant property to wool fabrics using the pad-dry-cure method.The results of the VFT and LOI tests indicated that the LOI value of wool fabrics was 30.1%after treating with 200 g/L DMBHP and 60 g/L BTCA,and the self-extinguishing of wool fabrics was still achieved after 25 washing cycles.The combustion behavior of wool fabrics was characterized by cone calorimeter test(CCT),and the results showed that the peak heat release rate(PHRR)of the flame-retardant wool fabrics decreased by 49.7%.These results indicated that DMBHP/BTCA treatment could significantly improve the flame retardant property and reduce the heat release of wool fabrics.Besides,the results of smoke density test and smoke toxicity analysis suggested that the DMBHP/BTCA treatment could reduce the release of smoke and and the concentration of released toxic gases was low.Based on the analysis of the TG,CCT and TG-IR test results of the fabrics after the flame retardant treatment,the DMBHP/BTCA system had the effect of flame retardant in condensed phase.(2)The phosphorus-containing poly carboxylic acid(2-phosphate-1,2,4tricarboxybutane)(PBTCA)was applied to improve the flame retardant performance of the wool fabrics by the pad-dry-cure way.The optimum process was obtained through single factor experiment:the concentration of PBTCA was 60 g/L;the immersion temperature was 60℃;the pH value of the immersion solution was 1;the curing temperature was 170℃;the curing time was 3 min.The results of the LOI test and VFT indicated that the damaged char length and LOI value of the treated wool fabrics with a weight gain of 11.8%was 40 mm and 40%,respectively,and the treated wool fabrics can still achieve self-extinguishing after 30 washing cycles.The combustion behavior of the finished wool fabrics was characterized by CCT,and the results showed that the PHRR and THR of the wool fabrics treated with PBTCA decreased by 38.6%and 37.0%,respectively.The above results indicated that the PBTCA treatment could effectively improve the flame retardant properties and reduce the heat release of the fabrics.The results of smoke density test and smoke toxicity analysis suggested that the addition of PBTCA could hinder the smoke production and the concentration of released toxic gases was low.In addition,combined with heat treatment,TG,DSC and other methods,it was found that PBTCA had the effect of increasing crosslinking and promoting char formation on wool fabrics.(3)A series of metal salt solutions were employed to wool fabrics by a simple technique to fabricate high-efficiency flame-retardant wool fabrics.There results of the LOI test and VFT indicated the wool fabrics finished with FeCl3 had the best flame retardant properties and the washability.That was to say,the LOI value of wool fabrics treated with 6%FeCl3 solution increased from 24.2%to 35.3%,and the wool fabrics can achieve self-extinguishing after 30 washing cycles.In addition,the combustion behavior of wool fabrics was investigated by CCT,and the PHRR of the treated wool fabrics were reduced by 49.6%,indicating that Fe3+ can effectively inhibit the heat release of wool fabrics.The results of smoke density test and smoke toxicity analysis suggested that the addition of FeCl3 could hinder on the smoke of wool fabrics and the concentration of released toxic gases was low.In addition,by comprehensively analyzing the TG test results of treated fabrics,the changes of residue morphology after CCT and LOI tests,and the XRD changes of wool treated at corresponding temperatures,it was found that Fe3+ catalyzed wool fibers to form char layer(below 450℃)and was transformed into form FezO3 layer(above 450℃),which both acted as a protective barrier,preventing further burning of the fibers and improving the flame retardant properties of the fabrics.In addition,the flame retardant properties and smoke suppression properties of wool fabrics treated with phosphorus-containing flame retardant agents and metal salts were investigated,finding that there was no phosphorus-metal synergy.