Fumed Silica Enhances the Flame Retardancy of Ammonium Polyphosphate/Urea/Di-Pentaerythritol Doped Silicone Acrylic Emulsion Coating

Abstract

In this study, a new intumescent flame-retardant coating based on silicone-acrylic emulsion is prepared using KH550-modified fumed silica, ammonium polyphosphate, urea, and di-pentaerythritol. The cone calorimeter (CC) test demonstrates that 0.50 wt% fumed silica significantly improves the flame retardancy of the coating. Compared with the coating without fumed silica, 0.50 wt% fumed silica reduces the total heat release (THR) of the coating from 18.00 to 16.38 MW m⁻², and the flame retardant index (FRI) increases from 1.00 to 2.03. Fumed silica enhances the strength of residues, as demonstrated by binding force compression curves and other tests. The yield force and compressive strength of residues increase by 91.26% and 94.12%, respectively. Moreover, thermogravimetric (TG) analysis shows that 0.50 wt% fumed silica enhances the thermal stability of the coating. In the pyrolysis kinetic analysis, the three-stage deceleration function (F₃) is selected as the pyrolysis function. The activation energy (E _α ) of the coating with 0.50 wt% fumed silica increases from 155.28 to 234.86 kJ mol⁻¹ at 370°C–410°C. The above conclusions show that fumed silica has great potential to improve flame retardancy and provides a new strategy for expanding the research field of flame retardant coatings.