The effect of zinc borate in combination with ammonium octamolybdate or zinc stannate on smoke suppression in flexible PVC

The effect of combinations of zinc borate with ammonium octamolybdate or zinc stannate on smoke suppression upon combustion of flexible PVC was studied. Effects on Oxygen Index and on residual char after ten minutes at 560°C were also evaluated. These studies were done using both a conventional dioctyl phthalate (DOP) plasticizer and a mixed plasticizer consisting of a 1:1 combination of DOP and an alkyl aryl phosphate ester. For both plsticizer systems, results showed that combinations of the zinc borate with either ammonium octamolybdate or zinc stannate gave an improved effect with respect to smoke reduction upon combustion. Thermogravimetric analysis (TGA) of PVC containing these additives showed no indication of interactions to explain this effect. TGA analyses indicated that PVC samples made with the mixed plasticizer had final decompositon temperatures which were slightly higher than those made with DOP as the plasticizer.