Influence of Polyphosphate Flame Retardant Couple with Ammonium Polyphosphate on Epoxy Resin?
A novel polyphosphate flame retardant, poly ( 2-10-hydrogen-9-oxa-phosphaphenanthrene hydroquinone phenyl phosphate) (POPP), aimed at improving the flame retardancy of EP was prepared. POPP and ammonium polyphosphate(APP) at the mass ratio of 1:2 were added into EP to form a series of flame retardant modified epoxy resin( FR-EP ) . The chemical bond adsorptions of FR-EP were investigated by infrared spectroscopic analysis. The thermal stability was study by thermal gravimetric analysis( TGA) . Flame retardant properties as well as burning behavior of epoxy resin composites have been investigated by limited oxygen index ( LOI ) and vertical burning test ( UL-94 ) . Fire properties of modified epoxy resin were test by Cone calorimeter. The morphological characteristics of char residue after Cone test were studied by scanning electron microscope( SEM) . The result shows that POPP increase burning behavior at lower adding amount, which help epoxy resin to pass UL-94 V-0 at 5%. But POPP modified epoxy resin gave out only 24. 2% of LOI value. POPP/APP flame retardant increase not only UL-94 grade but also much higher LOI value. A UL-94 V-0 grade was obtained when 5% POPP/APP were added into the epoxy matrix and 27. 7% LOI value. When adding amount of POPP/APP are increased to 15%, a higher LOI value of 33. 8% can be get. Results of TGA test indicate that decomposition temperature of FR-EP decrease along with increase of flame retardant amount. But modified samples give out more char residue. By incorporation of POPP/APP, THR, HRR, EHC, TSR and COP of FR-EP were reduced obviously, and promote char residue dramatically. PkHRR decrease from 831. 5 kW/m2 to 346. 8 kW/m2 at 15% of adding amount. Morphology study shows that good flame retardant property of FR-EP is contributed to well-formed char residue structure. These structures of char are net-like and type may prevent little burning product from moving out to the surface of matrix. Moreover, this char residue protects inner material from heat.
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