The flame retardancy and thermal degradation behaviors of trivalent metal-alginate films

Abstract

Alginate, one of the most abundant biodegradable and sustainable natural resources in the world, is an alternative to petroleum-based polymers (traditional plastics). The coordination structure, flame retardancy, thermal stabilities and degradation mechanism of aluminum alginate and iron alginate films were studied by Fourier transform infrared spectroscopy (FTIR), limited oxygen index (LOI), vertical burning (UL-94) and thermogravimetric analysis tests. The FTIR results showed that the coordination structures of aluminum alginate and iron alginate were correlated to the monodentate geometry and the bidentate chelating mode, respectively. The LOI values were 35·1 and 42·0 for aluminum alginate and iron alginate, respectively, and UL-94 of them achieved V-0 rating without any addition of other flame retardants, while the LOI value of sodium alginate was 24·5 with no UL-94 rating. The TG results showed that the addition of aluminum and iron cations catalyzed the decomposition of alginates in the lower-temperature zones, which exhibited the amounts of residues for aluminum alginate and iron alginate were less than that of sodium alginate. Compared thermal oxidative decomposition behaviors in air with those in N2, the oxygen in air did not take part in the thermal decomposition process in the lower temperatures.