Synthesis Of P-N-Si Flame Retardant Based On Nano-SiO₂ And Research Of Flame Retardant In Polyurethane

Polyurethane?PU?is one of the polymer materials that have been widely used in many different fields.However,its flammability is a serious threat to human life and property.Scientists have done a lot of researches on the flame retardant of PU.In recent years,with the development of nano-scientific technology?nanao-ST?,duing to their nanoscale effects,large specific surface area and strong interfacial interaction,nanocomposites have achieved far better performance than conventional materials obtained by blending methods.Nonacomposite material has become the focus of materials science.Nano silica has been widely used in the field of polymer flame retardants due to their low cost,excellent flame retardancy and smoke suppression.In this paper,eight P-N-Si flame retardants have been successfully prepared by using tetraethyl orthosilicate as the silicon source.Five flame retardants were selected for the modification of polyurethane according to the synthetic conditions and thermal properties.The main research contents are summarized as follows:1.Four silicon nanospheres with different topography are synthesized by different methods using tetraethyl orthosilicate?TEOS?as silicon source and ammonia?NH₃·H₂O?as catalyst.Silica microspheres?SiO₂?were synthesized by St?ber method.Mesoporous silica microspheres?mSiO₂?were synthesized by sol-gel method.Hollow silica microspheres?hSiO₂?were synthesized by hard template method.Hollow mesoporous silica microspheres?hmSiO₂?nanospheres were synthesized by ultrasonic stirring.Then,four kinds of silicon spheres were reacted with KH-550?APTES?to obtain four kinds of nanospheres of NH₂-SiO₂,NH₂-mSiO₂,NH₂-hSiO₂ and NH₂-hmSiO₂.The suitable conditions for amino modification of silica microspheres were investigated.The structures and morphology of the products were characterized by FT-IR,SEM and TEM.2.Twocyclicphosphorusoxychlorideintermediates3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphorus spiro[5.5]undecane 3,9-dioxygen?PDD?and 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide?DPPC?were obtained by Using pentaerythritol and neopentyl glycol as raw materials,respectively,and reacting with phosphorus oxychloride.The four aminated silica microspheres were reacted with two phosphoryl chlorides.Eight kinds of P-N-Si flame retardants?PDD-NH₂-SiO₂,PDD-NH₂-mSiO₂,PDD-NH₂-hSiO₂,PDD-NH₂-hmSiO₂,DPPC-NH₂-SiO₂,DPPC-NH₂-mSiO₂,DPPC-NH₂-hSiO₂,DPPC-NH₂-hmSiO₂?were obtained.Suitable reaction conditions were screened.The morphological characteristics of the flame retardant were characterized by SEM and TEM.The structures of products were characterized by FT-IR.The composition of products were characterized by EDX.The thermal properties of flame retardants were measuerd by TGA/DTG.3.Polyurethane foam was prepared by the enter water foaming craft using isocyanate?PM-200?and polyether polyol?4110?as main raw materials.By comparing the thermal properties of the eight flame retardants and the synthesis conditions,PDD-NH₂-SiO₂,PDD-NH₂-mSiO₂,PDD-NH₂-hSiO₂,PDD-NH₂-hmSiO₂and DPPC-NH₂-mSiO₂ were added to PU for modify flame retardant.The thermal properties of five flame retardant polyurethanes with different additions were investigated by vertical buring?UL-94?and limiting oxygen index?LOI?.Then the PU/PDD-NH₂-mSiO₂,PU/PDD-NH₂-hSiO₂ and PU/DPPC-NH₂-mSiO₂ were selected for Cone test to research its flame retardant properties more deeply.The structures of flame retardant polyurethane and carbon residue were characterized by FT-IR and SEM.Their thermal properties were characterized by TGA/DTG.Experiments show that the LOI of flame retardant PU increases with the increase of the amount of flame retardant.When PDD-NH₂-hSiO₂,PDD-NH₂-mSiO₂ and DPPC-NH₂-mSiO₂ are added in an amount of 30%,the LOI of of them reached 26.1%,25.9%and 24.0%,respectively,and UL-94 rating could reach to V-0 rating without melt dripping.SEM analysis showed that after combustion,the nanoparticles migrated to the surface of the carbon layer while forming a dense expanded carbon layer on the surface of the material.TGA/DTG tests show that all three flame retardant systems have good thermal stability.Moreover,compared with pure PU,the flame retardant have different degrees of decline in peak of total heat release rate?THR?,heat release rate?PHRR?,smoke production rate?SPR?and total smoke release?TSP?parameters of the three flame retardant systems.It is worth nothing that PU/PDD-NH₂-mSiO₂-30%has the best smoke suppression effect,which SPR,RSR,TSR and TSP reduced by39.7%,22.7%,41.5%and 41.9%compared to pure PU,respectively.Besides,PU/PDD-NH₂-hSiO₂-30%has the best flame retardant effect whose HRR and THR were 16.1%and 29.6%,which were lower than pure PU,respectively.