Thermal decomposition behaviour of polyamide fire-retardant compositions containing magnesium hydroxide filler

The thermal analysis of polyamides modified with magnesium hydroxide fire retardant filler is studied. Using combined TGA, DSC EGA and on-line FTIR techniques, it is shown that on thermal breakdown magnesium hydroxide exerts a significant pro-degraditive action on polyamides, attributed to water release and resulting hydrolysis of the polymer chain. Evolved gases released are shown to be water, carbon monoxide, carbon dioxide, ammonia and various hydrocarbon fragments. Similar results are obtained for both filled and unfilled PA compositions. However it is evident that in PA-6,6, polymer degradation occurs before magnesium hydroxide breakdown, whereas there is much greater overlap between thermal decomposition of PA-6 and the fire retardant filler.