| Cellulose fabrics,cotton fabrics and viscose fabrics,have been widely used due to their excellent softness,comfort,moisture permeability and dyeability,occupying a large market share in the textile industry.However,cellulose fabric is extremely flammable and easy to cause fire hazard,which greatly limits its application in some fields.In order to meet the fire safety requirements of textiles in the current market and application fields,flame retardant modification of cellulosic fabrics is particularly important.In recent years,with the increasing demand for high-quality flame retardant textiles,the flame retardant is promoted to develop in the direction of high efficiency,low toxicity and green.Phosphorus-nitrogen synergistic flame retardant is one of the main development directions of non-halogenated flame retardant technology.Nhydroxymethyl-dimethylacrylamide phosphate(Pyrovatex CP),as a typical representative of its commercialization,can give cellulose fabric high efficiency and durable flame retardant performance.However,there is formaldehyde release problem during the preparation and use process,which seriously endangers human health.Therefore,how to realize the halogen-free and formaldehyde-free high-performance design of flame-retardant cellulose fabric has become a research hotspot and difficulty at present.1,2,3,4-butanetetracarboxylic acid(BTCA)is a cross-linking agent commonly used in textile finishing.By utilize that excellent reactivity of BTCA with hydroxyl and amino groups,phosphorus-nitrogen flame retardant containing hydroxyl group/amino group can be covalently bonded with hydroxyl group of cellulose,and green and durable flame retardant cellulose fabrics can be prepared.In this paper,cotton fabric and viscose fabric were taken as research objects.Firstly,polyhydroxy branched phosphoramide(BPAE)was synthesized with phosphorus oxychloride and diethanolamine,and BTCA was used as cross-linking agent for flame retardant finishing.Although the flame retardant effect was good,the strength loss of fabric was serious.In order to reduce the influence of BTCA finishing system on the strength of fabric,the polyamino branched phosphoramide(BPEI-DP)with different phosphorus content and primary amino content was synthesized by introducing phosphate groups into branched polyethyleneimine molecules.The strong acid environment of BTCA was neutralized by BPEI-DP to reduce the strong damage caused by BTCA finishing system.In addition,the effects of flame retardant concentration,BTCA dosage,curing temperature and curing time on the flame retardancy and durability of the fabric were investigated,and the optimal flame retardant finishing process was determined.the flame retardant fabric with good performance was prepared.The flame-retardant property and washability were systematically studied,and compared with the Pyrovatex CP flame retardant on the market.The thermal stability,combustion behavior,physical and mechanical properties and flame retardant mechanism were also analyzed.The main research results are as follows:(1)BPAE and BPEI-DP4 flame retardant cotton fabrics have good flame retardant properties,with LOI values of 29.0% and 27.9% respectively,which can successfully pass the vertical combustion test and completely eliminate afterglow.The peak heat release rate(pHRR),total heat release(THR)and average effective heat of combustion(Av-EHC)all decreased,especially the pHRR and THR of BPAE flame retardant cotton fabric decreased by 63.5% and 37.3% respectively.In addition,the carbon forming ability of the treated fabric was improved obviously,and more char residues can be retained in the nitrogen/air atmosphere at 800 ?,and the char residue can maintain the complete fabric structure.The content of C/P element were increased and the content of O/N element were decreased,which indicated that the flame retardant had condensed phase and gas phase flame retardant mechanism.The LOI values of BPAE and BPEI-DP4 flame retardant cotton fabrics after 1 washing cycle were 27.0% and 26.4%respectively,and decreased to 25.8% and 24.9% after 20 washing cycles,which indicates that flame retardant fabrics have certain washing durability.However,the strength of BPAE flame retardant cotton fabric decreased obviously,while the strength of BPEI-DP4 flame retardant cotton fabric retained about 80%.(2)BPAE and BPEI-DP6 flame-retardant viscose fabrics show similar properties to flame-retardant cotton fabrics,with LOI values increased to 28.9%,successfully passed the vertical combustion test and eliminated afterglow,pHRR decreased by 59.5%and 33.5% respectively,but THR did not decrease significantly.Both BPAE and BPEI-DP6 can effectively promote the charring of viscose fabric,so that more residual char can be retained in the high temperature environment.In addition,a large number of bubbles were observed on the surface of char residue,and it was found that the content of C/P element were increased,while the element content of O/N were decreased,which proves that the flame retardant exhibits condensed phase and gas phase flame retardant mechanism.The LOI values of BPAE and BPEI-DP6 flame retardant viscose fabrics after 1 washing cycle were 26.6% and 26.1% respectively,and decreased to 25.3% and24.9% after 20 washing cycles,which indicates that flame retardant viscose fabrics have certain washing resistance.Besides,compared with BPAE flame retardant viscose fabric,the strength of BPEI-DP6 flame retardant viscose fabric can be better preserved. |
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