Combinations of cuprous oxide (Cu2O) and modified ammonium APP (EDA-APP ethanediamine ammonium polyphosphate) were tested as PIN flame retardant systems in epoxy/polyamide resin. The load of EDA-APP was 16-21% with 0-4% cuprous oxide. UL94-V0 (3.2mm) was achieved with 21% EDA-APP or 16.3% EDA-APP plus 1.7% cuprous oxide, whereas 25% APP was needed to achieve this.
The cuprous oxide showed to be effective in reducing smoke production rate, total smoke production and carbon monoxide (toxic gas) production, both in neat resin without flame retardant, and in combination with EDA-APP (PIN FR). The use of the PIN flame retardant plus cuprous oxide reduced both smoke and carbon monoxide emissions by a factor of around three, compared to neat resin. Analysis suggests that this is due to the synergistic and catalytic effects of cuprous oxide in accelerating char formation and improving the char structure.
“The synergistic effect of cuprous oxide on an intumescent flame-retardant epoxy resin system”, M-J. Chen et al., RSC Advances, issue 57, 2017 http://dx.doi.org/10.1039/C7RA05482C