A Phosphorus-Containing Inorganic Compound as an Effective Flame Retardant for Glass-Fiber-Reinforced Polyamide 6

A novel inorganic compound, aluminum hypophosphite (AP), was synthesized successfully and applied as a flame retardant to glass-fiber-reinforced polyamide 6 (GF-PA6). The thermal stability and burning behaviors of the GF-PA6 samples containing AP (flame-retardant GF-PA6) were investigated by thermogravimetric analysis, vertical burning testing (with a UL-94 instrument), limiting oxygen index (LOI) testing, and cone calorimeter testing (CCT). The thermogravimetric data indicated that the addition of AP decreased the onset decomposition temperatures, the maximum mass loss rate (MLR), and the maximum-rate decomposition temperature of GF-PA6 and increased the residue chars of the samples. Compared with the neat GF-PA6, the AP-containing GF-PA6 samples had obviously improved flame retardancy: the LOI value increased from 22.5 to 30.1, and the UL-94 rating went from no rating to V-0 (1.6 mm) when the AP content increased from 0 to 25 wt % in GF-PA6. The results of CCT reveal that the heat release rate, total heat release, and MLR of the AP-containing GF-PA6 samples were lower than those of GF-PA6. Furthermore, the higher additive amount of AP affected the mechanical properties of GF-PA6, but they remained acceptable. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2379-2385, 2011