Preparation of flame retardant and thermal insulation polystyrene foams via high internal phase emulsion template

Expanded polystyrene foam (EPSF), valued for its excellent insulation properties, faces a significant flammability challenge due to its cellular structure. Traditional flame retardant methods such as physical blending and layer-by-layer assembly have poor applicability to EPSF. Therefore, it is necessary to find other more effective methods for synthesizing flame-retardant EPSF. The high internal phase emulsion (HIPE) template is one of the simplest and most commonly used methods for synthesizing porous materials, which have features such as adjustable pore structures and high porosity. In this work, ammonium polyphosphate (APP)/starch was added to the dispersed phase of the HIPE to prepare the flame-retardant EPSF by one-pot method. The morphology, thermal stability and flame retardancy of the foams were investigated. When the addition of APP/starch (the weight ratio is 1:1) reached 30 wt.%, the peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR) of the composite foam decreased by 74.7%, 65.9%, and 24.7%, respectively, compared to the pure PS foam. Meanwhile, its limiting oxygen index (LOI) value reached 25.8%, and the UL-94 rating reached V-1 level, indicating significant improvement in flame retardancy. This study provides an effective strategy for synthesizing flame-retardant porous materials.