Synthesis and Application Studies of DOPO‐Based Organophosphorous Derivatives to Modify the Thermal Behavior of Polybenzoxazine

Abstract

The DOPO‐based flame‐retardant additives DOPO‐HQ, DOPO‐AP and DOPO‐Van were synthesized in varying numbers of phenolic hydroxyl groups and amine groups. Moreover, their influence on the polymerization of a bisphenol F‐based benzoxazine, as well as the thermal properties of the resulting materials, were studied. All DOPO‐based derivatives influenced the polymerization temperature onset with a reduction of up to 20 °C, while thermo‐mechanical properties re-mained high. Surprisingly, phosphorous content below 0.4 wt% significantly improved the reaction against small flames yielding an increase in the limited oxygen index by 2% and a V‐0 rating in the UL‐94 test. DOPO‐HQ proved to be the most effective additive regarding the reaction against small flames at an astonishingly low phosphorous concentration of below 0.1 wt%, whereas DOPO‐AP and DOPO‐Van simultaneously lowered the polymerization temperature.