Synthesis And Application Study Of Phosphorus Containing Flame Retardants And Curing Agents For Epoxy Resin

Two phosphorous/nitrogen containing diphenylphosphine oxide(DPO)derivative(DPO-SS)was designed and synthesized in this paper:(((sulfonyl bis(4.1-phenylene))bis(azanediyl))bis((2-hydroxyphenyl)methylene))bis(diphenylphosphine oxide)(DPO-SS)and((1,4-phenylene bis(azanediyl))bis(methylene))bis(diphenylphosphine oxide)(DPO-N).Their structures were confirmed by Fourier transform infrared spectroscopy(FTIR),nuclear magnetic resonance(NMR)and mass spectra(MS).Then a series of flame retardant epoxy resin with different phosphorus content were prepared by using DPO-SS and DPO-N as phosphorus-containing flame retardant and co-curing agent,4,4-diamino diphenyl sulfone(DDS)as curing agent.Thermal properties of flame retardant epoxy resin(F-EP)were investigated by thermogravimetric analysis(TGA)and dynamic thermomechanical analysis(DMA).DMA results indicated that both DPO-SS and DPO-N modified F-EP had little fluctuation in glass-transition temperature(Tg).The Tg of DPO-SS and DPO-N modified F-EP with 0.5 wt%P were 143.2 and 142.6 C respectively.While the Tg of pure EP was 148.5 C.DMA results showed that DPO-SS and DPO-N would be decomposed in advance and promote the decomposition of epoxy resin(EP)in low temperature zone.But they could prevent the further decomposition of the EP and lead to a higher char residual mass in the high temperature zone.The flame retardance property of F-EP were tested by vertical burning test(UL94)and limited oxygen index(LOI).The results showed that both DPO-SS and DPO-N could endow EP with excellent flame retardant properties.DPO-SS and DPO-N modified F-EP with 0.5 wt%P could reach UL94 V-0 level.And the LOI value were 29.1 and 29.2%respectively.The results of cone calorimeter test manifested that both DPO-SS and DPO-N could decrease the release of heat and smoke during burning.The flame retardant mechanism of DPO-SS and DPO-N modified F-EP were studied by video screenshots during UL-94 test,pyrolysis/gas chromatogram/mass spectrometry(Py-GC/MS),FTIR spectra of the char residues after UL94 test,digital images and scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS)images of residual char after cone calorimeter test.The results manifested that DPO-SS and DPO-N had flame retardance effect both in gas phase and condensed phase.Water absorption and dielectric properties testing results showed that DPO-SS and DPO-N could reduce the water absorption,dielectric constant and dielectric loss.of the epoxy resin under the appropriate adding amount.