| Polyurethane（PU）,a widely used polymer materials,has been applied to various areas.However,polyurethane burns rapidly that have a potential threat to the safety of human life and property security.Many researches about flame retardancy of polyurethanes have been reported.With the increasing awareness of environmental protection,halogen-containing flame retardants with potential pollution risks have been gradually replaced.The development of flame retardant systems from bio-based resources is suitable for supporting the requirements of sustainable development and environmental protection.In this paper,eight bio-based intumescent flame retardants have been successfully prepared,which based on the characteristics of polyhydroxyl structure of starch and high phosphorus content of phytic acid.1.A novel starch based flame retardant（PSTM）has been prepared by the reaction of hydrolyzed starch,phytic acid and melamine.The effects of the dosage of sodium phytic acid,reaction temperature,reaction time and pH on phosphorus content have been explored.The product structure was characterized by FT-IR,31PNMR,XRD and SEM.Thermal performance was characterized by TGA/DTG.2.A series of Schiff bases were synthesised by reacting of PST and amino.Through the addition of P-H bond and imide group（C=N）reaction,seven oxidized starch based flame retardants with high phosphorus content（POSTM,POSTE,POSTH,POSTP,POSTA,POSTY,POSTD）were synthesized respectively.The structure and thermal properties of the compounds were measured by FT-IR,31P NMR,XRD and TGA/DTG.3.Based on entire water foaming craft,the PU/IFR had been prepared by adding different proportions of PSTM,POSTM,POSTP and POSTA respectively to Polyether polyol（4110）and isocyanate（PM200）.Their structures of PU/IFR were characterized by FT-IR and SEM.Limiting oxygen index（LOI）tests,vertical burning（UL-94）tests,and cone calorimetric（Cone）tests were carried out to investigate the combustion of the PU/IFR.Char residue yield of the PU/IFR composites is enhanced in TGA test and the values of LOI are increased significantly,suggesting the improvements in thermal stability and flame retardancy.When the usage of PSTM,POSTM,POSTP and POSTA reaches 30%,the LOI of flame retardant PU is achieved25.6%,26.9%,25.7%,25.1%respectively,and UL-94 rating could reach to V-0without melt dripping.Char morphology observation demonstrated that PU/IFR could promote the formation to form more intact intumescent char structure.Due to the presence of-NH2 or-OH in PU/POSTM-30%and PU/POSTP-30%flame retardant structure,they can bond with raw materials of PU and form the carbon layer with a better continuous density and high expansion.Moreover,the flame retardancy of the PU/IFR composites was enhanced,which was evidenced by the markedly reduced heat release rate（HRR）,total heat release rate（THR）,smoke production rate（SPR）and total smoke release（TSR）obtained from Cone tests.It is worth noting that PU/POSTM-30%has the best flame retardant effect whose HRR and THR are 23.2%and 19.7%,which are lower than pure PU respectively.In addition,PU/POSTP-30%has the best smoke suppression effect,with SPR,RSR,TSR,and TSP reduced by39.7%,32.5%,44.1%,and 38.7%compared to pure PU,respectively。... |
