A flame retardant containing dicyandiamide and aluminum hypophosphite for polyethylene

Polyethylene (PE) is a widely used industrial plastic, but its flammable feature limits its further application. A novel composite based on dicyandiamide (DICY) and aluminum hypophosphite (AHP) was integrated into PE. FT-IR confirmed the chemical structures of the composite. During vertical burning and limiting oxygen index tests, the UL-94 flame retardant grade reached level V-0 and the LOI index increased from 18.8% to 26.3% when the ratio of AHP and DICY was 4: 1 (occupying 20 wt% of PE). The CCT tests showed the peak heat release rate of 4-AHP/DICY (AHP: DICY = 4: 1) decreased from 620.3 to 323.4 kW/m2 compared with pure PE. Moreover, the carbon residue of 4-AHP/DICY was higher than that of other samples. After cone calorimetry tests, a compact and stable carbon layer formed on the surface of PE composites through the digital photographs and SEM images of the char residue.