An Investigation Of The Halogen Free Flame Retardant Moisture-curing Sealants

During the last decade,there has been a considerable attention in moisture-curing MS sealant and PU sealant.However the application of MS sealant and PU sealant is restrained because of their poor flame resistence.The conventional IFRs usually require high loading,causing negative effect on mechanical properties of moisture-curing sealants.Therefore it is important and necessary to study flame retardant moisture-curing sealants.The main contents of this paper are as follows:(1)Synthesis and characterization of silane terminated polyether:silane terminated polyether was synthesized by the addition reaction between trimethoxy-silane and allyl polyether with Pt catalyst under no solvent condition.The silane terminated polyether structure was confirmed by FTIR and 1H-NMR;(2)Synthesis and characterization of intrinsic polyurethane prepolymer:The phosphorus-containing polyether was introduced into the polyurethane prepolymer to synthesize intrinsic flame-retardant polyurethane.The intrinsic flame-retardant polyurethane was confirmed by FTIR;(3)Halogen-free flame retardant of silane terminated polyether(MS)sealant:This paper mainly investigated the relationship between three kinds of fillers(Calcium carbonate(CaCO3),magnesium trisilicate(MTS)and mullite(AS))in sealant and the intumescent flame retardants(IFR).MCC date showed that IFR could decrease the peak heat release rate(PHR)and total heat release(THR)of MS/MTS/IFR and MS/AS/IFR.When the IFR addition was 54 phr,the LOI and the vertical burning level of the MS/CaCO3/IFR sample was 22.8%and no rating in the UL94 test.The MS/MTS/IFR sample had a LOI values of 22.8%and UL94 grade of VO;MS/AS/IFR sample was 22.8%and UL94 VO level.FTIR and XRD results indicated significant synergistic effects between silicates and IFR,enhanced the carbon layer formation and improved the flame retardant properties;The introduction of lanthanum to MTS and AS could cause negative effects on the flame retardancy in MS sealants.(4)The halogen-free flame retardancy of polyurethane sealants:The fire performance of flame retardant polyurethane prepolymer(P-PU)with different phosphorus content was investigated.The results showed that the flame retardancy of P-PU was improved with the increase of phosphorus content.when the phosphorus content was 2.05%,the LOI and the vertical burning level of P-PU reached 32.1%and VO respectively.Experiments showed that the flame resistance of P-PU sealant was better than that of PU sealant.IFR were then introduced into sealant to further enhance the flame resistance.The results showed the LOI and the vertical burning level of P-PU/TCP/AS/IFR(100/15/30/30)was increased to 28.4%and with a VO UL94 grade.It is suggested that IFR and P-PU can synergistically enhance the char formation of the PU sealant.