Flame-retardant and thermal degradation mechanism of low-density polyethylene modified with aluminum hypophosphite and microencapsulated red phosphorus

Aluminum hypophosphite (AHP), a novel flame retardant, was used to improve the flame retardancy of low-density polyethylene (LDPE) with microencapsulated red phosphorus (MRP). The synergistic effect between MRP and AHP was investigated by the limiting oxygen index (LOI), vertical burning test (UL-94), and thermogravimetric analysis. When the contents of MRP and AHP were 10 and 30 phr, the LOI of LDPE/10MRP/30AHP composite was 25.5%, and it passed the UL-94 V-0 rating (the number before "MRP" and "AHP" is the loading of MRP and AHP, In LDPE/10MRP/30AHP, the content of the LDPE, MRP and AHP is 100phr, 10phr and 30phr, where phr refers to parts per hundreds of resin). The results of cone calorimetry testing show that the heat release rate of the composites was significantly reduced, and the strength of the char layer improved when the loading of AHP increased. The thermal stability of the LDPE/10MRP/30AHP composite was enhanced. The structure of the char was investigated by Fourier transform infrared spectrometry and scanning electron microscopy/energy-dispersive spectrometry. The results indicate that AHP promoted the formation of stable char. This research provided a good way to prepare flame-retardant materials with a halogen-free flame retardant and contributed to environmental protection. (c) 2015 Wiley Periodicals, Inc.