Synthesis Of New Environment-friendly Flame Retardants And Its Application In Rigid Polyurethane Foam

Rigid polyurethane foam (RPUF) is a kind of heat insulation material with an excellentperformance in heat insulation, which have a remarkably broad range of applications inconstruction, pipe, cold storage, due to their desirable properties such as low density, finediffuse barrier properties, excellent shock absorption and strong adhesion with other materials.However, the RPUF is very easy to burn and can produce a lot of smoke. It not only easilycause casualties, but also will increase the difficulty of the fire-fighting, which limits theapplication of RPUF. One of the key problems that is imperious need to be solved is toimprove the flame retardant and smoke suppression performance of RPUF while keeping itsexcellent properties to make it adapt to the widely application of RPUF. In this paper, twoaspects for the flame retarded RPUF were studied including organic intumescent flameretardant and organic inorganic hybrid flame retardant.A kind of functional intumescent flame retardant, N-(P,P′-diphenyl) phosphorus-based-(3-triethoxysilicon) propylamine(DPTP), were synthesized and its molecular structure werecharacterized by elemental analysis, Fourier transform infrared spectroscopy(FTIR), nuclearmagnetic resonance (NMR).Thermal gravimetric analysis(TGA) and the high-temperatureignition experimental results show that DPTP have excellent char formation either in anitrogen or air atmosphere. The DPTP carbon residue is shown to have a perfect graphitecrystal structure by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Ramanspectroscopic analysis.DPTP can greatly improved retardant properties of RPUF. The limiting oxygen index(LOI) increased from18.2to27.3after adding10phr DPTP to RPUF, and significantlyreduce the heat release rate, Total heat release and mass loss rate. The compression strength ofRPUF closely related to the cell structure,and DPTP has "stabilizing the foam" and "theplasticizing effect". Adding a small amount of DPTP, the compression strength of RPUF canbe improved, however increasing the amount of DPTP, the compression strength of RPUFcould be reduced.DPTP was covalently grafted onto the MMT to obtain D-MMT, and its structure wascharacterized, results showed that the graft rate reached32.9%. The layer space of D-MMThave increased, and D-MMT having excellent thermal stability and char-forming ability. Thelayers of D-MMT were dispersed in RPUF with nano scale, which perfected the foam cellstructure, so as to enhance the compression strength for RPUF.Compared with pure RPUF, when adding10phr D-MMT, the PHRR of composite material was reduced by33.6%, the THR was reduced by47.1%, the PSPR was reduced by78.6%, and the TSP was reduced by68%, the compression strength of composite increased to203KPa. A composite with flame-retardant, smoke suppression and enhancement wasprepared.When the composite material were burning, the DPTP through formatting intumescentcarbon layer and releasing nonflammable gas to reach fire retardant, the nanoscale dispersedMMT extend the flammable gas transmission path through the "maze effect "and effectivelybarriered heat penetration to play the flame retardant. The carbon layer formed by DPTP canfill the gap and the spacing between the edge of MMT sheet layer to forming dense, completecarbon layer, Dispersion in carbon layer of MMT can have the effect of strong carbon layers.So, the flame retardant and smoke suppressing properties of material were greatly enhancedthrough organic-inorganic synergistic effect.