The Effect Of Aramid Fiber Honeycomb Core On The Fire Resistance And Mechanical Properties Of Isocyanate-based Polyimide Foam

Isocyanate-based polyimide foam(IBPIF)has great physical and chemical properties such as low density,heat insulation,great thermal stability,irradiation ressitance and sound absorption owning to imide rings and porous structure.The paper presents a one-step method to prepare IBPIFs,finds a kind of process that foams are filled in honeycomb core by free foaming in ambient temperature.And it successfully prepares aramid fiber honeycomb reinforced isocyanate-based polyimide foam(IBPIF/HC)with different honecycomb perforated size and its chemical structure,porous structure,thermal properties,fire resistance and mechanical properties are analyzed.First,by researching the effect of aramid fiber honeycomb core on chemical structure,porous structure,fire resistance and mechanical properties of IBPIFs,it finds that the honeycomb core has no effects on chemical and porous structure of polyimide foams but has some influence on its fire resistance and mechanical properties because of high flame retardant and spatial structure of honeycomb cores.So,IBPIF’s limiting oxygen index value improves 36.68%and pkHRR,pkSPR and TSR decrease 29.72%,40.82%and 30.20%,respectively.HRR and SPR curves become greatly slow.Honeycomb improves the foam’s compression strength of P,L and W direction 2700%O52.22%and 32.95%,respectively.Then,by researching the effect of spatial structure like honecycomb perforated size(d)and its angle(0)on fire resistance and mechanical properties,it finds that the wall of honeycomb hole has obstructing function to combustion.Flame suprresion becomes better with d decreasing.When 0 becomes smaller,the walls have crosswise and longitudinal obstructure functions,hinder the spread of flame from top to bottom.When 0=0°,pkHRR value decreases to 152.06 kJ.With d increasing,synergistic effect between honeycomb and foam becomes weaker and compression strength of IBPIF/HCs decrease.Finally,we study the effects of aramid honeycomb on fire resistance of IBPIFs with different imidization degree.The research demonstrates that the increase of imidization degree improves the heat duration,fire resistance but decreases its own mechanical properties.Then,we prepare IBPIF/HC.With increasing imidization degree,LOI arrives at 40%and pkHRR and pkSPR decrease.What’s more,HRR,SPR curves have a significant reduction.Aramid fiber honeycomb core has decreasing effects on improving the fire resistance of IBPIF but increasingly improves its mechanical properties with the increasing imidization degree.