ISPA Synthesis And Mechanism Investigation And Its Flame Retardancy Research On Cotton

Cotton fabric is the most widely used textile in the world becouse it is soft and comfortable to wear and has good water permeability and breathability. But its limiting oxygen index value is low, it is highly flammable, it would burn when exposed to combustion source and resulted in fires. Statistics show that50%of fires were caused by burning textile each year. A wide attention is paid to the flame-retardant textiles. The most widely used halogen flame retardant meet Dioxin problem, some EU countries took part containing halogen flame retardant for the hazard assessment. People’s request of improving the life quality and healthy standard becomes higher that urgently needs to replace halogen series flame retardant. After halogen flame retardant, halogen-free flame retardant are constantly emerging, such as phosphorus based flame retardant, nitrogen flame retardant and inorganic nanocomposite material.A novel intumescent flame retardant, imidazole spiro-cyclic phosphoramidate(ISPA) has been synthesized by the reaction of spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride(SPDPC) with imidazole. The ultraviolet and visible spectrophotometer was used to determine the optimum reaction conditions which is dichloromethane as the solvent, triethylamine as catalyst, reflux6hours, raw material molar ratio (SPDPC:imidazole) was1:2.4. And the product was characterized by elemental analysis and fourier transform infrared spectroscopy.ISPA was used as the flame-retardant to finish cotton fabric in the presence of catalyst and crosslinking agent. Orthogonal experiment was designed to find out the best experimental conditions combining with the combustion performance and mechanical performance. The influence of flame tetardant, crosslinking, catalyst agent and curing temperature on the flame retardant properties and mechanical properties was discussed. The thermal degradation behavior, buring behaviour and surface morphology of the flame retardant finishing cotton under optimum condition were investigated. The results showed the better flame retardant finishing process is30%ISPA,1.5%catalyst,1%crosslinking agent and pre-baking time is5min under80℃, curing time is3min under150℃. For the flame retardant finishing cotton under optimum condition, LOI is33.96%, afterflame time is0s, afterglow time is0s, damaged length is64mm, breaking force is312.05N which reaches B1level of the fabric flame retardant standard. The thermal analysis results show that the initial decomposition temperature of flame retardant cotton significantly reduced than that of untreated cotton. Untreated cotton fabric has almost no residue at600℃and the treated cotton fabric has30%carbon residue that means ISPA has a good char formation quality. Cone calorimetry test results show that the flame retardant cotton has lower heat release rate(HRR) than that of untreated cotton. Total heat release(THR) of untreated cotton is4.02MJm-2kg-1, reduce to2.48MJm-2kg-1of the flame retardant cotton fabric, was reduced by38.3%. Effective heat of combustion(EHC) of finished cotton was reduced and the specific extinction area(SEA) was increased proved improving the flame retardancy of the cotton fabric.The surface morphology of the untreated and treated cotton before and after cone calorimetry were assessed by scanning electron microscopy(SEM). Finished cotton with metal oxide suppressed the smoke release, reduced the fire hazard. Comparing the surface morphology of untreated and flame retardant cotton fabric, it can be seen that the flame retardant has been adhered to the cotton fiber. Untreated cotton fabric shrinked after incomplete combustion and larger gaps were formed between the yarns, in the meantime the surface morphology of carbon residues of the flame retardant cotton fabric after combustion is uniform, continuous, compact.