Preparation of a New Type of Expansion Flame Retardant and Application in Polystyrene

Polystyrene (PS) is a widely used building insulation material with good mechanical strength and strong temperature adaptability. However, PS itself is highly flammable and displays poor flame retardancy. At present, building fires caused by organic external wall thermal insulation materials prepared from PS represent a new fire hazard. In this study, the addition of an intumescent flame retardant (IFR) to reduce the flammability of PS was achieved. Using melamine (MEL), acrylonitrile-styrene-acrylate (ASA), and phytic acid (PA) as raw materials, a new type of flame retardant (MAP) was prepared by an electrostatic self-assembly method and was introduced to modify PS. Its effect on the flammability of PS composites was also investigated. The flammability of the PS composites was characterized using the limiting oxygen index (LOI) and vertical combustion. The effect of MAP on the morphology of the carbon layer formed from polymer decomposition was studied using scanning electron microscopy (SEM). By adding MAP to a PS/20%N-IFR flame-retardant composite, the flame-retardant property was significantly improved, the limiting oxygen index reached 37, and the vertical combustion reached a V-0 level. The fire performance index (FPI) of the PS/20%N-IFR composite reached 0.0054, which was significantly higher than that of the control PS (0.037) as determined by the cone calorimetry test. The SEM results showed that the introduction of MAP can increase the density of the carbon layer after combustion. The heat release rate for combustion was reduced. In addition, the mechanical properties of the PS/20%N-IFR composites were compared with those with no flame retardant. The tensile strength of the PS/20%N-IFR composite was 26.1 MPa and the elongation of the PS/20%N-IFR composite remained at 2.2%. The PS/20%N-IFR composite displayed better flame retardancy than the untreated material and good mechanical properties. The presence of MAP prevented the heat and oxygen transfer and interrupted the releasing of flammable products, thus protecting the PS from burning. This flame-retardant material may find broad applications in building insulation materials.