Aluminium (AlW), tin (II) (SnW) and zinc (ZnW) tungstates were previously found to increase char formation in polyamide 6.6 (PA66), but have never before been studied for their potential as synergists when present with phosphorus-containing (PFRs) flame retardants. We investigate this gap in the scientific knowledge in this publication. Tungstate-PFR interactions of PA66 composites were investigated by thermal analysis, limiting oxygen index (LOI), UL94, cone calorimetry and evolved gas analysis (TGA-FTIR).

Of the three tungstates, AlW in the presence of aluminium diethylphosphinate (AlPi) or a mixture of AlPi and melamine polyphosphate (MPP), promotes the highest level of flame retardancy in terms of a balance of high LOI, V-rating and TGA residual char in air at 500 °C and reduction in cone calorimetric peak heat release rate (R_PHRR = 80%). This observation has been related to AlW having the highest Lewis acidic properties. While zinc tungstate displays the lowest levels of interaction with either PFR, it shows significant smoke suppressant properties.

Elemental analysis of cone calorimetric chars suggests that while some loss of phosphorus occurred from SnW/AlPi/MPP-containing composites, most likely via volatile diethyl phosphinic acid formation, nearly 10% reduction also occurred in the Sn/W molar ratio indicating some volatilisation of tin. The TGA (in air)-FTIR results for carbon dioxide, ammonia and hydrocarbon fuel species evolution enabled discussions of the effect that each tungstate had on the flame retardant mechanisms operating.

先前发现铝（AlW），锡（II）（SnW）和锌（ZnW）钨酸盐会增加聚酰胺6.6（PA66）中的炭形成，但以前从未研究过它们与含磷的增效剂的协同作用（ PFRs）阻燃剂。我们在此出版物中调查了科学知识方面的这一差距。通过热分析，极限氧指数（LOI），UL94，锥形量热法和逸出气体分析（TGA-FTIR）研究了PA66复合材料的钨酸盐-PFR相互作用。

在这三种钨酸盐中，在高的LOI，V额定值和TGA残留炭的平衡方面，在二乙基次膦酸铝（AlPi）或AlPi和三聚氰胺多磷酸酯（MPP）的混合物存在下的AlW促进了最高的阻燃性。在500°C的空气中加热，并降低锥形量热峰放热率（R _PHRR  = 80％）。该观察结果与具有最高路易斯酸性的AlW有关。钨酸锌与两种PFR的相互作用最低，但具有显着的抑烟性。

锥形量热炭的元素分析表明，虽然含SnW / AlPi / MPP的复合材料发生了一些磷的流失，最有可能是通过挥发性二乙基次膦酸的形成，但Sn / W摩尔比也发生了近10％的降低，这表明了一定量的挥发。锡。TGA（空气中）-FTIR的二氧化碳，氨气和碳氢化合物燃料种类演变结果使人们能够讨论每种钨酸盐对阻燃机制运行的影响。