Synthesis and properties of a novel phosphorous-containing flame-retardant hardener for epoxy resin

An aryl phosphinate dianhydride 1,4-bis(phthalic anhydride-4-carbonyl)-2-(6-oxido-6H-dibenz[c,e][1,2]-oxaphosphorin-6-yl)-phenylene ester (BPAODOPE) was synthesized and its structure was identified by FTIR and 1H-NMR. BPAODOPE was used as hardener and flame retardant for preparing halogen-free flame-retarded epoxy resins when coupled with another curing agent. Thermal stability, morphologies of char layer, flame resistance and mechanical properties of flame-retarded epoxy resins were investigated by thermogravimetric analysis, SEM, limiting oxygen index (LOI), UL-94 test, tensile, and charpy impact test. The results showed that the novel BPAODOPE had a better flame resistance, the flame resistance and char yield of flame-retarded epoxy resins increased with an increase of phosphorus content, tensile strength and impact strength of samples gradually decreased with the addition of BPAODOPE. The flame-retarded sample with phosphorus contents of 1.75% showed best combination properties, LOI value was 29.3, and the vertical burning test reached UL-94 V-0 level, tensile strength and impact strength were 30.78 MPa and 3.53 kJ/m2, respectively. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013