A zinc oxide – organic triazine compound (OTCA-ZnO) was prepared and tested as a flame retardant in EVA (ethylene-vinyl acetate polymer) in combination with APP (ammonium polyphosphate) at total loading of 25% (App 0-25%, OTCA-ZnO 25-0%) by melt-mixing. OTCA-ZnO particles showed average size around 100 nm and better dispersion in EVA than zinc oxide (reaction of the ZnO surface hydroxyl groups). At 16-20% APP and 9-5% OTCA-ZnO, UL94-V0 (3.2 mm) was achieved, LOI was increased from 17% to 30%, melt-dripping was reduced and peak smoke production rate was reduced by more than 60%. These effects are considered by the authors to result from retention of P, N and Si in the char, so strengthening the char structure.
“Enhancement of an organic–metallic hybrid charring agent on flame retardancy of ethylene-vinyl acetate copolymer”, B. Xu et al., Royal Society Open Science, 6: 181413, http://dx.doi.org/10.1098/rsos.181413