Novel phosphorus-based flame retardants containing 4-tert-butylcalix[4] arene: Preparation and application for the fire safety of epoxy resins

A novel flame retardant (FR) containing phosphorus and 4-tert-butylcalix[ 4] arene was synthesized and characterized. The FR combined with ammonium polyphosphate (APP) was then incorporated into epoxy resins (EPs) at different ratios. The flame retardancy, thermal stability, and smoke-releasing properties were investigated. The limiting oxygen index was as high as 30.8% when the mass fraction ratio of the FR to APP was 1:2. The improved FR effect have been due to the combined FR effects between the FR and APP. The char residue content at 800 degrees C under a nitrogen atmosphere increased notably from 8.22% to 17.6% when the FR APP was incorporated into EP; this indicated an improvement in the thermooxidation resistance. From the cone test, we found that both the total heat-release and peak heat-release rate of the FR resins were reduced. Compared to the resins containing no FRs, the smoke-production rate and total smoke-production results indicate that the FR resins also exhibited good smoke-suppression properties. Generally, the stable char layer of the FR APP-EP not only effectively prevented the release of combustion gases but also hindered the propagation of oxygen and heat into the interior substrate. (C) 2017 Wiley Periodicals, Inc.