An aluminium hypophosphite showed better overall performance in PA66 than magnesium or zinc hypophosphites. Lab scale tests of dicylohexyl hypophosphites of aluminium, magnesium and zinc were tested in polyamide 66 (PA66). The PIN FRs were blended into melted PA66 at 250°C, press moulded to sheets, then tested for fire performance (LOI, UL 94), tensile and flexural strength. All three metal salts showed a flame retardant effect in PA66. The magnesium salt showed the lowest thermal stability and lowest fire performance. The dicylohexyl aluminium hypophosphite showed the best overall performance, maintaining material strength and achieving UL 94 V-0 (3 mm) at 10% loading. LOI increased from 28% to 32% at 15% (nearly +50%) at 15% loading.
“Comparative Study on the Flame-Retardant Properties and Mechanical Properties of PA66 with Different Dicyclohexyl Hypophosphite Acid Metal Salts”, H. Zhang et al., Polymers 2019, 11, 1956; https://dx.doi.org/10.3390/polym11121956