Low density polyethylene (LDPE) is widely used industry, construction, electronics, furniture and elsewhere because of its low weight, low toxicity, electrical insulation and performance, but is highly flammable.
Aluminium hypophosphite (AHP) was tested as a flame retardant at 30-60 phr (parts per hundred resin) showing improvement of limiting oxygen index (LOI) from 19% in neat LDPE to 27.5% and achieving UL 94-V0 (4 mm) at 50 phr. FTIR (Fourier transform infrared spectrometry) showed that AHP reduces the content of olefins (and so of combustible gases) in fire gases. The aluminium and > 96% of the phosphorus remain in the char, which is compact and includes P-O-C bonds which improve its thermal stability.
“Study of using aluminum hypophosphite as a flame retardant for ‐density polyethylene”, S. Tian et al., Fire and Materials. 2017;1–10, http://dx.doi.org/10.1002/fam.2443