Preparation And Performance Of Flame Retardant Lignosulfonate Based Rigid Polyurethane Foam

Lignonsulfoante,a natural macromolecule containing aromatic rings and abundant phenolic and aliphatic hydroxyl groups,was used to substitute part of diethylene glycol and copolymerized with isocyanate to produce lignonsulfonate based rigid polyurethane foams with foam formation once.Thermogravimetric analysis,the limiting oxygen index,cone calorimeter test,scanning electron microscopy and other analysis methods are used to investigate the thermal properties and flame retardancy based on additive ratio of flame retardant trichloropropylphosphate and dimethyl methylphosphonate,the lignosulfonate content and the ratio of lignosulfonate/ammonium polyphosphate intumescent flame retardant system.The flame retardant mechanism was analyzed and discussed.Several main conclusions which are listed thereinafter were obtained.?1?By using single-factor lignosulfonate content analysis lignonsulfonate was used to substitute part of diethylene glycol to synthesize and optimized lignonsulfonate based rigid polyurethane foams.Results showed that when the diethylene glycol was replaced by 15 wt% lignin,the thermal stability and flame retardant characteristics of lignonsulfonate based rigid polyurethane foam LRPUF3 were the best.Moreover,the limiting oxygen index of lignonsulfonate based rigid polyurethane foam LFRPU2 with additive some flame retardants trichloropropylphosphate and dimethyl methylphosphonate was 26.5% as well as water absorption and dimensional stability,which can be satisfied with the B2 level materials of GB/T 8624-2012.And the flame retardant mechanism was contributed to gas phase flame rearant.?2?Lignonsulfonate/ ammonium polyphosphate flame retardant system was investigated on the thermal properties and flame retardancy of rigid polyurethane foam.The limiting oxygen index of lignonsulfonate/ ammonium polyphosphate flame retardant rigid polyurethane foams were increased with an increase of lignonsulfonate content which indicated that lignonsulfonate can use as a flame retardancy materials due to is aromatic structures and carbon-to-carbon bonded.When lignonsulfonate based rigid polyurethane foam containing 15 wt% of lignosulfonate L₁₅ RPU give rise to the best thermal stability.The mean heat release rate and the total heat release decreased in same trends of rigid polyurethane foams L₁₅ RPU and L20 RPU which are 46% and 50%,respectively.And the effective heat combustion decreased 23% and 31%,respectively.What's more,the L₁₅ RPU foam of the time-to-peak carbon monoxide production postponed 96 s than that of pure rigid polyurethane foam,suggesting that lignosulfonate would be mainly act on the flame retardancy with higher char production within the function of ammonium polyphosphate.Also with a stable quality of the water absorption and dimensional stability.Fourier transform infrared spectroscopy characterization was conducted to study the change of hydrogen bonding during the formation of urethane bond after polymerization.When the lignonsulfonate content was between 15%²0 wt% based on diethylene glycol the intensity of hydrogen bonded in carbanyl group of urethane increased respectively,which affect the thermal performance and combustion properties of lignosulfonate/ ammonium polyphosphate intumescent flame retardant rigid polyurethane foams.?3?Lignosulfonate as employed as carbonization agent and ammonium polyphosphate as acidic source and a blowing agent,the lignonsulfonate/ ammonium polyphosphate intumescent flame retardant system was investigated on the thermal properties and flame retardancy of rigid polyurethane foam,with the flame reradancy mechanisim.A suitable phosphorus/nitrogen/carbon ratio in the intumescent flame retardant system was studied for its flame retardancy.Results showed that at the lignosulfonate to ammonium polyphosphate ratio of 1:5,the limiting oxygen index of lignosulfonate based rigid polyurethane LRPU5 was reached 30.5% and LRPU5 give rise to the lowest effective heat combustion value,less smoke release rate and total smoke production,mean carbon monoxide production and char residue,with 10%,26%,25%,68% and 35%,respectively.The best fire retardancy is obtained at 1:5 of lignosulfonate to ammonium polyphosphate ratio,which can be satisfied with the B1 level materials of GB/T 8624-2012.Moreover,the flame retardant mechanism of the intumescent flame retardant system was referring to condense phase flame rearant.