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Intumescent Flame Retardant Epoxy Resins Based on Condensation Polymers of P-Phenylenediamine and Bispirocyclic Pentaerythritol Diphosphate

Copolymer of p-phenylenediamine and bispirocyclic pentaerythritol diphosphate was synthesized and characterized by FTIR and 1H NMR. This polymer was used to prepare epoxy resin/SPDA composites. Thermal stability of SPDA and epoxy/SPDA composites were investigated by thermogravimetric analysis (TGA), and their flammability were investigated by the LOI test. TGA results showed that the addition of SPDA improved the char residue of epoxy resin. SEM investigation showed that the residual chars have a honeycomb-like structure, indicating an intumescent ﬂame retarding effect of SPDA in composites. In addition, all of above results confirmed that accelerate carbonization play a key role in improving flame retardancy of epoxy resin.