Preparation And Properties Of Flame Retardant Rigid Polyurethane Foam Plastics

In china, building energy consumption has account for one-third of the total socialenergy consumption. With the fast rates of urbanization and industrial structure adjustment,building energy consumption will be beyond industry and transportation energy consumption,and eventually be the first place of the social total energy consumption. Therefore，thereseaches on saving building energy consumption are of great importance. Rigid polyurethanefoam (RPUF) is a kind of heat insulation materials with outstanding performance, which has aremarkably broad range of applications in building insulation field. But the popularization andapplication of RPUF is limited for its flammability and toxicity of smoke. Therefore, takeingthe research of new environmentally friendly flame retardant rigid polyurethane foam plasticshas very important practical significance.In this paper, polarization microscope, SEM, mechanical performance testing, horizontaland vertical combustion, oxygen index, cone calorimeter test, thermal stability analysis andother analysis methods are used to investigate the influence of the three different flameretardant systems (UC, DMMP/UC, DMMP/EG) on RPUF structure and performance, andthe flame retardant mechanism of three kinds of flame retardant system was analyzed anddiscussed. Several main conclusions which are listed thereinafter were obtained.(1) Urea (UC) can speed up the foaming reaction of RPUF, deteriorate its cellularstructure and reduce its compression strength. With the increase of UC adding amount, thistrend is strengthening. UC can improve only the flame retardant performance of RPUFslightly, but the addition of urea could significantly improve the smoke suppressionperformance and carbon residue rate under800℃, and with the increase of adding amount ofUC, smoke suppression effect is enhanced, the late thermal stability of RPUF is improved.From the view of flame retardant smoke suppression effect, UC is a kind of nitrogen flameretardants which place gas phase flame retardant first, condensed phase flame retardantsecond.(2) Dimethyl methyl phosphonate (DMMP) cooperate with UC filled RPUF exist varioussynergism.When the mass ratio of DMMP to UC is10to30, the pore structure, compressionstrength and time to ignition (TTI) of the composite are the best, the peak of heat release rate (PHRR) and total heat release (THR) of the composite reach the minimum, the synergisticeffect of the two is the best. While the mass ratio of DMMP/UC is30/10, the limiting oxygenindex (LOI) of RPUF reaches the maximum. There is no synergism between DMMP and UCin the smoke suppression and thermal stability, but the addition of DMMP/UC cansignificantly increase carbon residue rate of the RPUF. DMMP/UC is a kind of the compositeflame retardants which has gas phase and condensed phase bipolar synergistic flame retardantmechanism.(3) DMMP and EG have obvious synergistic effcet in flame-retardant RPUF. WhenDMMP/EG is10/30, the synergism of the two is the best. RPUF has the best flame retardantperformance; the TTI, LOI, PHRR, THR, smoke produce rate (SPR) and total smokeproduction (TSP) of RPUF reach optimal values. But in improving the pore structure, thecompression strength and thermal stability of composite materials, they have no synergisticeffect. The addition of DMMP could increase the density and strength of "vermicular"expansion carbon layer, and significantly improve the flame retardant and smoke suppressionperformance of composite materials. The decomposition products (PO and PO2) can alsoplay a role in gaseous phase, and make DMMP/EG become a kind of composite flameretardants which give priority to condensed phase flame retardant and take gas phase flameretardant as a supplement.