Preparation And Properties Of Flame Retardant Bio-Based Polyurethane Foam

At present,the raw materials for the preparation of polyurethane foam(PUF)are mostly petroleum-based.With the continuous advancement of the national carbon neutralization strategy,how to introduce biomass resources into the PUF system has attracted wide attention of researchers.In addition,because a large number of porous structures and organic components in the PUF system make it highly flammable,the limiting oxygen index(LOI)is only about 19.0%,which greatly limits its application.Therefore,it is of great significance to develop a kind of flame retardant polyurethane foam based on biomass raw materials.In this paper,cashew phenolic glycidyl ether was used as raw material to prepare cashew phenolic polyol,which was introduced into the polyurethane foam system.By changing the structure of isocyanate and the type and amount of flame retardant,the related properties were studied from the internal and external factors.Bio-based flame retardants were also synthesized using phytic acid as raw material to replace some petroleum-based phosphorus flame retardants.Sodium lignosulfonate was added to further improve the flame retardant properties of polyurethane foam and enhance the introduction of biomass resources.The main contents are divided into the following sections:(1)Study on the properties of bio-based PUF based on different isocyanates.Cardanol-based polyol was synthesized by the reaction of cardanol-based glycidyl ether and diethanolamine.The structure of the product was characterized by Fourier transform infrared spectroscopy(FT-IR)and nuclear magnetic resonance(~1H-NMR).A series of PUFs were prepared by mixing cashew phenolic polyols with polyether polyol PTMG-1000,adding toluene-2,4-diisocyanate(TDI),isophorone diisocyanate(IPDI)and hexamethylene diisocyanate(HDI),respectively,and adjusting the amount of flame retardant ammonium polyphosphate(APP).The physical structure,mechanical properties,thermal stability and combustion behavior were studied by scanning electron microscope(SEM),universal material testing machine and cone calorimeter.The results showed that as the structure of isocyanate changed from aliphatic chain to aromatic ring,the pores of PUF changed from open pores to closed pores,that is,from soft polyurethane foam to rigid polyurethane foam,and the addition of APP increased the pore size of PUF.Due to the low crosslinking degree caused by high reactivity,the thermal stability of PUF prepared by TDI is poor.The introduction of APP improves the final residual carbon rate of the system and thus improves the flame retardant performance.The limiting oxygen index can be increased from 17–18%to 22–23%.Among them,the comprehensive performance of PUF prepared by TDI,an aromatic isocyanate,is significantly better.After the addition of flame retardant,the total heat release(THR)and average effective combustion heat(Av-EHC)are 14.7 MJ/m~2 and 19.9 MJ/kg,respectively,which are lower than those of the other two.(2)Study on preparation of PUF based on cardanol polyol and phytic acid flame retardants.Modified phytic acid flame retardant(MPA)was prepared by triethylamine(TEA)modified phytic acid(PA).A series of PUFs were prepared by changing the feed ratio of cardanol polyol to polyether polyol PTMG-1000 and controlling the addition amount of MPA.The physical structure,basic properties,thermal stability and combustion behavior of PUF were studied by SEM,universal material testing machine and cone calorimeter.The results showed that with the increase of bio-based polyol content,the prepared PUF gradually became rigid polyurethane foam,and the pore size decreased first and then increased.The introduction of modified phytic acid also affected the morphology of PUF.Due to the unsaturated long carbon side chain of cardanol polyols,the thermal stability of PUF gradually decreased with the increase of its introduction amount.The introduction of MPA would reduce the thermal stability of PUF in the early stage,but it could improve the final carbon residue rate.The higher the content of cardanol polyols was,the higher the carbon residue rate was.The introduction of MPA can increase the limiting oxygen index from 17-18%to22-23%,and the higher the content of cashew phenolic polyols,the better the performance.The Av-EHC of PUF prepared by introducing pure cardanol polyol into MPA was 9.1 MJ/kg,which was much lower than that of PUF without MPA and with less cardanol polyol introduction,which also proved the effectiveness of MPA introduction.(3)The performance of bio-based PUF prepared by different content of sodium lignosulfonate.On the basis of introducing MPA,trichloropropyl phosphate(TCPP)was added as a flame retardant,and a series of PUFs were prepared by dispersing sodium lignosulfonate(S-L)in diethylene glycol(DEG)and taking cardanol polyols as the main body and changing the amount of sodium lignosulfonate.The physical structure,basic properties,thermal stability and combustion behavior of PUF were studied by SEM,universal material testing machine and cone calorimeter.The results showed that with the increased of sodium lignosulfonate content,the pore size of PUF increased first and then decreased.When the content exceeded 10 wt%,the porosity increase的,and the compressive strength increased first and then decreased,which was proportional to the change of PUF density.In addition,the thermal stability of PUF also decreased with the increase in the amount of sodium lignosulfonate,and the residual carbon rate showed an upward trend.The limiting oxygen index of PUF reached 28.1%and 30.0%when the amount of sodium lignosulfonate was 10wt%and 15 wt%,respectively,which reached the flammable standard.Av-EHC also decreased from the initial 26.2 MJ/kg to 19.1 MJ/kg.