Short noteNovel high Tg flame retardancy approach for epoxy resins

A novel halogen-free phosphorus- and nitrogen-containing heterocyclic flame retardant - 5,10-dihydro-phenophosphazine-10-oxide (DPPA) - was synthesised and characterised by NMR, MS, and XRD analyses. DPPA and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were successfully incorporated in the backbone of diglycidyl ether of bisphenol A (DGEBA). The resultant prepolymers were cured with 4,4′-diaminodiphenylmethane (DDM) and diethyldiamino toluene (DETDA 80). The burning behaviours of the thermosets obtained were studied by UL 94 and LOI and compared to each other. Also their glass transition temperatures (Tgs) were determined by differential scanning calorimetry (DSC). Due to the bridging incorporation of DPPA in DGEBA by fusion process, high Tgs for these samples were achieved.