A nitrogen heterocyclic/phosphaphenanthrene derivative as a reactive additive for simultaneous improvement of flame retardancy, mechanical and dielectric properties of epoxy resins

Various approaches have been successfully applied to solve the flammability of epoxy resin (EP) materials, but enhanced flame retardance of EP is often along with deteriorated glass transition temperature (Tg) and mechanical property. In order to prepare EP composites with good comprehensive performance, we synthesized a phosphorus-containing triazole derivative named TBO from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 3,5-diamino-triazolz and salicylaldehyde, and attached it into epoxy framework. With 0.75 wt% phosphorus loading, the 0.75-TBO/EP composite had a V-0 rating and a limiting oxygen index of 33%. 1.0-TBO/EP composite also had a V-0 rating and acquired a decrease of 37.6% in peak heat release rate. In addition, the tensile strength and flexural strength of 0.75-TBO/EP increased to 63.9 MPa and 146 MPa from 59 MPa and 134 MPa of EP respectively. Meanwhile, the Tg values of TBO/EP elevated to some certain compared to EP. In a word, EP modified with TBO composites owned strong mechanical property, higher Tg and excellent flame retardance, indicating great potential for application.