Novel flame-retardant epoxy composites containing aluminium β-carboxylethylmethylphosphinate

Abstract

A novel flame-retardant aluminum β-carboxylethylmethylphosphinate [Al(CEP)] was synthesizedby a simple process. The effect of Al(CEP) on the curing of epoxy resin (EP) was investigated with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. The flame retardancy and thermal properties of Al(CEP)/EP were analyzed by a limiting oxygen index (LOI), vertical burning test (UL-94), scanning electron microscopy (SEM) with energydispersive X-ray (EDX), gravimetric analyses, and DSC. Results disclosed that curing of EP is delayed by incorporating Al(CEP). The flexural strength of EP is reduced but the flexural modulus is increased by adding Al(CEP). Adding Al(CEP) depresses the decomposition of EP while leads to a increase in the glass transition temperature (Tg), in char formation and in flame retardancy of EP. EP containing 25 phr Al(CEP) provides LOI of 28.3% and passes UL-94 V-0 rating. SEM results show that the sample passing V-0 rating can form the condensed char whereas porous char is observed from the sample failing in V-0 rating after combustion. EDX analysis shows that the condensed char presents higher weight ratio of carbon to phosphorus than the porous char, indicating appropriate amount of Al(CEP) is necessary for formation of the stable char. POLYM. ENG. SCI., 55:657-663, 2015.