Melaminium molybdate smoke and fire retarders for poly(vinyl chloride)

Melaminium molybdates are shown to be very effective smoke and fire retarder additives for PVC. In a simple tin stabilized rigid PVC compound the preferred melaminium β‐octa‐molybdate outperformed MoO3 and other common molybdenum smoke retarders. Combinations of melaminium molybdates with compounds of copper formed very efficient smoke‐reducing and char‐forming synergistic additive systems for PVC. For example, combining the octamolybdate with a series of different copper compounds consistently gave smoke reductions of about 85% in the flaming mode of the NBS Smoke Chamber at a total additive level of 5 parts per hundred parts of PVC. These large reductions in smoke were accompanied by large increases in the amount of char formed and retained as combustion residues.