SynopsisThe combination of mixture diagrams and quality functions can be a straightforward and rapid method of simultaneously optimizing polymer formulations for both flame retardancy and smoke suppression. For a semirigid PVC formulation using a three-component additive mixture it was found possible to raise the limiting oxygen index by over 7 units, while simultaneously reducing smoke production by more than 20%.
INTRODUCTIONMetal oxides are widely used as either flame retardants (FR) or smoke suppressants (SS) for a wide range of combustible organic polymers. In a recent paper we reported the FR/ SS effects for a range of inorganic and organometallic iron-containing compounds, including iron oxides, incorporated into a flexible PVC formulation.' Antimony and zinc oxides were also studied. Organoiron derivatives were found to possess both FR and SS properties, and ferrocene itself, for example, in a formulation at 1.0 phr (part per hundred of PVC) was found to raise the limiting oxygen index, LOI, by about 3 units while depressing smoke production, as measured by the U.S. National Bureau of Standards (NBS) test, by 28%, whereas the metal oxides studied tended to exhibit either FR or SS properties but not both. Of the iron-containing additives investigated, the oxides were the most effective smoke-suppressants, with an effectiveness similar to the commercial zinc /magnesium oxide preparation Ongard 11, although the LO1 enhancement ( < 2 units) of both these additives is small. On the other hand, antimony (111) oxide is an excellent flame retardant, raising the LO1 by 6.8 units at 5.0 phr, but with substantially increased smoke production ( +40% ). We report here the results of an investigation into the threecomponent additive system, antimony/ iron /zinc oxides, which has used chemometric methods to identify synergic effects and to rapidly develop an optimum formulation for semirigid PVC which has both good SS and good FR properties.
Background Theory
