Thermal conduction and fire property of glass fiber-reinforced high impact polystyrene/magnesium hydroxide/microencapsulated red phosphorus composite

A series of flame-retarded high impact polystyrene/magnesium hydroxide/microencapsulated red phosphorus (HIPS/MH/MRP) composites reinforced with different amounts of glass fiber (GF) were prepared by melt compounding. The thermal conduction behavior of the GF-reinforced HIPS/MH/MRP composite before ignition was studied by embedding thermocouples inside the composite at different depths along the thickness direction. The fire property of the composite was investigated by limiting oxygen index (LOI), UL-94, cone calorimeter test (CCT), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). It has been shown that the presence of GF promotes thermal conduction from surface area to the interior in the composite and the thermal inertia of the composite increases with GF loading. Because of increase in thermal conductivity and decrease in specific heat capacity, the heat on the sample surface can be transferred to the interior of composite more quickly than neat polymer and the temperature near the surface area of the GF-containing composite is reduced appreciably, which leads to delayed thermal degradation of polymers and increased difficulty of ignition. The incorporation of GF can increase the thermal stability, flame retardancy and smoke suppression of this composite simultaneously. The introduction of 2 wt% GF can hinder melt dripping of the HIPS/MH/MRP (100/30/10) composite and upgrade the UL-94 rating of this composite from V-1 to V-0. Thermal degradation of the polymer is retarded and no wicking effect occurs in this composite. Furthermore, the composite containing GF produces more residue and less smoke upon combustion. On the whole, the addition of GF not only increases thermal conduction and mechanical property, it also further improves fire safety of the flame-retarded HIPS/MH/MRP composite. The optimal mass fraction of GF is around 30 wt%.