Phosphorus‐containing terephthaldialdehyde adducts—Structure determination and their application as flame retardants in epoxy resins

Abstract

Abstract Two novel phosphorus‐rich prepolymers based on epoxy novolac and terephthaldialdehyde and potential flame retardants, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and 2,8‐dimethyl‐phenoxaphosphin‐10‐oxide (DPPO) were synthesised. The resultant flame‐retardant epoxy resins were cured with 4,4′‐diaminodiphenylmethane (DDM) and 4,4′‐diamino‐dicyclohexylmethane (PACM). Their flammability and burning behavior were characterised by UL 94 and LOI and compared with analogue prepolymers based on diethylphosphite (DEPP). The glass transition temperatures were determined by DSC measurements. Furthermore, the structures of two exemplary molecules based on p ‐tolylaldehyde adducts were examined by XRD and NMR analysis to determine the possibilities of linking the two novel DOPO and DPPO derivatives to the backbone of the epoxy resin. Additionally, the char yields were determined by TG analysis and thermal desorption mass spectroscopy of the thermosets used and compared with each other to obtain more information about the possible mode of flame‐retardant action of the different phosphorus compounds. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008