Thermo-oxidative degradation behavior and fire performance of high impact polystyrene/magnesium hydroxide/microencapsulated red phosphorus composite with an alternating layered structure

High impact polystyrene (HIPS) based composite filled by magnesium hydroxide (MH) and microencapsulated red phosphorus (MRP) with an alternating layered structure was prepared through layer-on-layer laminating. One of the two alternating layers consists of HIPS matrix filled by MH and MRP and the other layer is composed of pure HIPS. Thermo-oxidative degradation behavior and fire performance of the alternating composite were investigated in detail. It is shown that the flame retardants are dispersed alternately along the thickness direction of the composite. Thermo-oxidative degradation of the alternating composite is hindered appreciably. The alternating composite can not only produce more residue upon thermal degradation and burning, the residue is also more continuous and compact than that produced by its homogeneous counterpart with identical loading of flame retardant. Due to shielding effect of the compact char residue layer, thermal transmission along the thickness direction of the alternating composite is impeded noticeably under forced flaming conditions. On the whole, the alternating composite exhibits better thermo-oxidative stability, flame retardancy, smoke suppression and decreased toxic gas release in contrast with its homogeneous counterpart containing the same amount of flame retardant. This work provides another method to further improve the flame retardancy and smoke suppression of polymer composites.