Synthesis of a novel phosphorus-containing polysiloxane and its use as the modifier of thermal properties of an epoxy resin

A novel epoxy resin modifier, phosphorus-containing epoxide siloxane (PES) with pendant epoxide and cyclic phosphorus groups in the side chains of the polysiloxane backbone, was synthesized via the ring-opening, reaction of epoxy siloxane (ES) with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). H-1 NMR and FT-IR measurements were employed to characterize its chemical structure. The PES at various ratios was used to modify a bisphenol A epoxy resin (Ep828) by pre-reaction with curing agent 4,4'-diaminodiphenylmethane (DDM). The cured samples were investigated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and limited oxygen index (LOI). The results showed that the epoxy resins modified with PES exhibited higher glass transition temperatures (Tg), higher initial degradation temperatures (T-d 5 %) and better flame retardancy than the unmodified.