Silica micropearls (several nm diameter) were surface modified with three different phosphorus compounds (phosphoric acid, dihydrogen ammonium phosphate and diammonium phosphate) by reacting in ethanol with treatment agents.
10% of neat modified silica was tested in PBT (polybutylene terephthalate) polymer. The three phosphorus modified silica is showed high effectiveness as flame retardants in PBT, reducing peak heat release by up to 60% and also increasing time to ignition, due to char generation and bubbling of PBT in melting, so limiting heat transfer. The authors conclude that the synergy of phosphorus and silica can be effective in flame retarding the performance engineering plastic PBT, because the silica slows down polymer decomposition as well as favouring char formation.
“Effect of phosphorous-modified silica on the flame retardancy of polybutylene terephthalate based nanocomposites”, J. Courtat et al., Polymer Degradation and Stability 143 (2017) 74e84 http://dx.doi.org/10.1016/j.polymdegradstab.2017.06.014