The Flame Retardancy Improvement And Preparation Of Sodium Lignosulfonate Flame Retardant Polyurethane Foam

Polyurethane foam(PUF)has many advantages such as low density,high compressive strength,stable chemical properties,and good thermal insulation effect,which is applied to all aspects of human life.However,PUF materials without flame-retardant treatment were extremely easy to burn,and a large amount of toxic gas would be generated during the combustion process,which greatly limits its application range.At the same time,as the shortage of petroleum resources had become more and more serious,biomass-based composite functional materials had received widespread attention,lignin and was the second largest natural polymer material in nature after cellulose.Which had become current research hotspots.Therefore,the research and development of new environmentally friendly polyurethane flame-retardant foam has extremely high application value.This paper first used sodium lignosulfonate(SLS)as an additive and directly added it to PUF materials to prepare sodium lignosulfonate-based polyurethane foam(PUF/SLS)materials.The experimental results showed that when the addition amount of SLS was 10wt%,the limiting oxygen index(LOI)value of PUF/10wt%SLS material reacheed 20.7%.The TGA test showed that the addition of SLS reduced the initial thermal decomposition temperature of the material,but also reduced the maximum thermal degradation rate of the material,and at the same time the carbon residue content of the material at 700? had also increased to 26.8%.The CONE test results show that,compared with pure PUF materials,the heat release rate(HRR)and total heat release(THR)of PUF10wt%/SLS material were significantly reduced,and the residual carbon content after the test was also slightly increased.The addition of SLS maked the surface of the carbon layer more continuous and uniform after burning,and at the same time the firmness of the carbon layer was increased.The formed carbon layer protected the internal PUF material,thereby improving the flame retardant performance of the material.In terms of compressive strength performance,the compressive strength of PUF/SLS material is significantly reduced.When the addition amount of SLS is 10wt%,the compressive strength of PUF/SLS material is only 51.91 kPa.In order to further expand the utilization rate of SLS,SLS was used to replace part of the polyether polyol,and dimethyl methylphosphonate(DMMP)was added as a flame retardant to prepare PUF/SLS/DMMP flame retardant materials through the "one-step method".The experimental results showed that when the substitution rate of SLS was 80wt%and the addition amount of DMMP was 30wt%,the LOI value of PUF/80wt%SLS/30wt%DMMP material reached 27.3%.The TGA test results showed that the addition of SLS and DMMP reduced the maximum thermal degradation rate of PUF materials and increased the carbon residue content of the materials at 700?.CONE test results showed that the addition of SLS and DMMP reduced the heat release rate,total heat release and total smoke release of the material.After the test,the residual carbon content of the material had also increased to 37.3%.After the test,the surface of the residual carbon was smooth,continuous and dense,and the firmness of the carbon layer was also improved,so as to achieve the purpose of flame retardant modification.Compared with pure PUF material,the compressive strength of PUF/80wt%SLS material is greatly reduced to only 38.51 kPa,while the compressive strength of flame-retardant modified PUF/80wt%SLS/30wt%DMMP material gradually recovered to 126.82 kPa.SLS and ammonium polyphosphate(APP)were used to form an intumescent flame retardant(IFR)and applied to the flame retardant modification of PUF materials to prepare new flame retardant PUF materials.The experimental results showed that when the compound ratio of SLS and APP was 1:1 and the addition amount of IFR was 30wt%,the LOI value of the flame-retardant PUF material reached 27.3%.The TGA test results showed that the addition of IFR reduced the maximum thermal degradation rate of the material,and greatly increased the amount of carbon residue in the material at 700?.The CONE test results showed that the addition of the flame retardant IFR reduced the heat release rate of the material,and the total heat release was also reduced from the original 12.7 MJ·m-2 to 9.8 MJ·m-2,a reduction of 22.8%.After testing,the residual carbon content of PUF/30wt%IFR material had also been greatly increased,from 20.2%to 35.9%.The formed carbon layer was more expanded,continuous,dense and smooth.The carbon layer could play a role of better insulation and protection,thereby inhibiting further combustion and degradation of internal materials,and improving the thermal stability and flame retardancy of the materials.Compared with pure PUF material,the compressive strength of PUF/30wt%IFR material is significantly improved,reaching 216.71 kPa,which meets the requirements of category ? of insulation materials in the national standard for rigid polyurethane foam materials for building thermal insulation.In order to further improve the flame retardant properties of PUF materials,DMMP and IFR were used to form a synergistic flame retardant(FR)synergistic flame retardant PUF material to prepare PUF/FR materials.The experimental results showed that when the synergistic mass ratio of IFR and DMMP was 1:1 and the addition amount of FR was 30wt%,the LOI value of PUF/30wt%FR material reached 29.2%.The TGA test results showed that the addition of the synergistic flame retardant system advanced the initial thermal decomposition temperature of the material,reduced the maximum thermal degradation rate of the material,increased the carbon residue of the material at 700?,and improved the thermal stability of the material.The CONE test results showed that the synergistic flame retardant system reduced the heat release rate and total heat release of the material by 66.2%and 43.3%,reaching 82.8 kW·m-2 and 7.2 MJ·m-2.At the same time,the material had been tested The residual carbon content had also increased to 32.3%.From the results of the analysis of the carbon residue morphology,it could be seen that the addition of the synergistic flame retardant promotes the carbon formation of the material,and the formed carbon layer was firmer,more continuous and dense,and could play a more excellent protective effect.Compared with pure PUF material,the compressive strength of PUF/30wt%(DMMP+IFR)material is increased to 214.21 kPa.Compared with PUF/30wt%IFR material,the compressive performance is slightly reduced.