Functionalizing mesoporous silica with a nano metal–organic phosphonate towards mechanical-robust, thermal-resistant, and fire-safety epoxy resin

Epoxy resin (EP) has featured many industrial and practical applications, but was plagued by its inherent flammability. Herein, a hybrid flame retardant (mSiO 2 @TETP) was fabricated by in-situ immobilizing tin ethylenediamine tetramethylene phosphonate (TETP) on the mesoporous silica (mSiO 2 ) surface, and was used to prepare mechanical-robust, flame-retardant, and thermal-resistant EP composites. It is found that the introduction of only 1.0 wt% mSiO 2 @TETP into EP leads to a 20.5%, 19.7%, and 12.8% incremental tensile modulus, tensile strength, and impact strength, respectively. The EP composite with 5.0 wt% mSiO 2 @TETP (EP/mSiO 2 @TETP-5) succeeds to the UL-94 V-0 grade, with a limiting oxygen index value of 29.0%. And the peak heat release rate, total heat release, peak smoke production rate, total smoke release, and peak CO production rate of EP/mSiO 2 @TETP-5 decrease by 54.0%, 52.1%, 53.9%, 51.1%, and 55.7%, respectively in contrast with the values of pure EP. Moreover, the introduction of mSiO 2 @TETP results in an improvement in both the charring capacity and the initial thermal resistance (an increment in the glass transition temperature) of EP.