Experimental evaluation of tri‐hydrated aluminium in fire‐retardant properties of glass fibre reinforced polymers

Summary This paper presents an experimental investigation of alumina trihydrate (ATH) in glass fibre reinforced polymers (GFRP), aiming to determine the influence of ATH concentration on improved flame‐retardant properties. For this research, different concentrations of ATH: 37 phr (parts per hundred resin), 40, 47.5, 50 and 55 phr, were added in isophthalic polyester matrix composites reinforced with E‐glass fibre through a pultrusion process. These composites were tested for flammability and flame propagation using the mass loss calorimeter cone (MLCC), limiting oxygen index (LOI) and glow wire tests. Simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) was performed to evaluate the thermal stability and enthalpy. These analyses assessed the effectiveness and influence of each ATH concentration. It was observed in the MLCC tests that the ATH concentration of 40 phr reduced the peak heat release rate (PHRR) by 27% compared to a composite with 37 phr. All specimens showed the desired commercial result for wires and cables in the glow wire test since the composites reached the maximum glow wire flammability index (GWFI) of 960 °C and a glow wire ignition temperature (GWIT) above 900 °C. Thus, the addition of ATH above 40 phr leads to an improvement in the flame‐retardant properties of glass fibre reinforced polymers.