Study On Fire Security Of Rigid PIF By Phosphorus-containing Polyol And EG-based Additives

Isocyanate-baesd polyimide foam(IBPIF)is a kind of functional materials obtained by free-foaming method.Compared with polyimide foam via two-pot process,IBPIF has the possibility of application in the general civilian field due to its lower cost of production and simpler preparation process.Ususally,IBPIF has poor fire safety and soft texture,which cannot match the performance requirement of building insulation material in civilian field.These defects greatly limit the application of IBPIF.To address the two problems of poor fire safety and insufficient mechanical properties at present,the density of RPIF materials can be effectively iproved by closed mold method in this thesis.In addition,the rigid IBPIF(RPIF)materials with sufficient fire security are prepared by introducing additives with the effect of flame retardancy and smoke suppression.The main research contents are as follows.Firstly,the reactive flame retardant phosphate-containing polyol(PPCP)is prepared by hydroxylation modification of dimethyl methylphosphonate via transesterification.It can be efficient grafted on the RPIF resin skeleton,solving the serious volatilization problem of phosphorus-containing liquid flame retardants in the preparation process of RPIF.It is found that PPCP can not only effectively enhance the mechanical properties of RPIF materials,but also greatly improve the flame retardancy of RPIF.Obviously,the self-extinguishing of RPIF-0-5 can be achieved after leaving the flame and total heat release(THR)reduces to 3.98MJ/m~2.In addition,the limit oxygen index(LOI)reaches to 25.9%,having the highest growth rate.However,the addition of PPCP will increase the amount of smoke toxic gas released.Among it,the peak of smoke production rate(PSPR),total smoke production(TSP),total CO production(TCOP),HCN concentration,and flameless maximum smoke density(Ds max)of RPIF-0-10 are 0.048 m~2/s,0.95 m~2,0.38 g,32.57 ppm,and 40.96,respectively.It seriously affects combustion security of RPIF.Secondly,to solve the existent problem caused by individual addition of PPCP,expandable graphite(EG)are further added into slurry.The series of RPIF materials are prepared by the combination of EG and PPCP.It is found that the introduction of EG will damage the mechanical properties of RPIF.However,the synergy effect of PPCP and EG can significantly improve the fire safety of RPIF,solving the shortage of the two flame retardants separately used.RPIF-10-5 has the best fire safety,the LOI,PHRR,PSPR,TCOP,flameless Ds max,and HCN concentration are 30.9%、85 k W/m~2、0.025 m~2/s、0.22 g、23.15,and 13.64ppm,respectively.Thirdly,in order to further reduce smoke emission behavior of RPIF,EG/MH are encapsulated by magnesium hydroxide(MH)nanosheets.It is used in combination with PPCP to prepare series RPIF by adjusting the packaging amount of MH.The research show that EG/MH can better disperse in white slurry than EG,which effectively improve the mechanical properties of RPIF materials.Unfortunately,with the dosage of MH,flame retardancy of RPIF materials is reduced.The LOI of RPIF-10(30)-10 decreases to 28.0%,as well as PHRR and THR increase to 88 k W/m~2 and 4.17 MJ/m~2,respectively.However,EG/MH has a very obvious effect on smoke elimination,which can respectively decrease the PSPR and TSP of RPIF-10(30)-10 to 0.032 m~2/s and 0.74 m~2 and reduce the smoke density of RPIF-10(30)-10by about 80%.