Effect of hydrated fillers and red phosphorus on the limiting oxygen index of poly(ethylene-co-vinyl actate)-poly(vinyl butyral) and low density polyethylene-poly(ethylene-co-vinyl alcohol) blends

The limiting oxygen index (LOI) values of EVA-PVB and low density polyethylene (LDPE)-poly(ethylene-co-vinyl alcohol) (EVOH) polymer blends containing hydrated filler-type flame retardants and red phosphorus were measured. When used as the sole flame retardant, magnesium hydroxide [Mg(OH)(2)] and alumina trihydrate (ATH) performed best in EVA and PVB, respectively. Magnesium hydroxide addition had a limited effect on the LOI of plasticized PVB, and addition of red phosphorus made little difference. This result is attributed to a mismatch between the decomposition temperature of Mg(OH)(2) and the temperature at which the PVB plasticizer vaporizes. Otherwise, low-level addition of red phosphorus significantly improved LOI values. The presence of hydroxyl groups on the polymer backbone had a beneficial effect with respect to LOI values in ATH-filled blends. An LOI value of 30 was achieved in EVOH with as little as 32% of ATH and 3% of red phosphorus.