A exp 119m Sn Mossbauer Study of Tin/Molybdenum Oxidic Systems as Flame Retardants and Smoke Suppressants for Rigid PVC

Tin(IV) oxide, either alone or in combination with melaminium beta -octamolybdate or Mo(VI) oxide, has been found to be an effective flame retardant/smoke suppressant for rigid PVC. exp 119m Sn Mossbauer spectroscopy has been used to study the chemical changes undergone by the Sn species during: (a) thermal degradation and (b) combustion. Under these conditions, the SnO sub 2 is partially reduced to Sn(II) species (SnCl sub 2 and SnO) and metallic beta -Sn. Elemental analysis of the char residues indicates that a proportion of the Sn and Mo is lost from the polymer (possibly as volatile metallic chlorides or oxychlorides) and it is suggested that these metals can operate as fire retardants in both the condensed and vapour phases. 35 ref.--AA