The optimization of the smoke suppressant and flame retardant properties of flexible PVC

Abstract

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

ZnS as fire retardant in plasticised PVC

“…Antimony oxide (Sb 2 O 3 ) has been established as a suitable flame retardant for PVC‐P by exploiting the synergism between Sb 2 O 3 and organic halide compounds 3–6. Different combinations of flame retardant Sb 2 O 3 with smoke suppressants like iron oxides,7–10 zinc borate11, 12 or zinc hydroxystannate13–16 have been discussed with the objective of optimising flame retardancy in respect to fire risks and fire hazards. Recently, zinc sulphide (ZnS) was proposed as a promising fire retardant for PVC‐P especially in mixtures with Sb 2 O 3 creating synergism of ZnS and Sb 2 O 3 17.…”

Flame retardant flexible poly(vinyl chloride) compound for cable application

“…In recent years zinc compounds were used widely because of the high flame retardancy and smoke suppression, of compounds such as zinc borate (ZB), 8 -12 zinc sulfate (ZnSO 4 ), 13 and Ongard, 14 and ZnO/MgO solid solution, 15,16 Use of solid solution flame retardants (SSFR) is reported in several patents, but work on the system and the mechanism of SSFR has not been reported on yet. In this respect some work has been done by us was to check the effect of ZnO/MgO, ZnO/CaO, and ZnO/MgO/CaO solid solution on flame retardancy, thermal degradation, mechanical and electrical properties of plasticized PVC compounds that are required for power cables.…”

A study on properties and morphological structure of ferrocene-filled PVC

“…Some publications show that addition of a small amount of ferrocene can improve both flame retardance and visible smoke suppression of PVC. [5][6][7] Concerning its mechanism, Lawson 11 describes how the formation of ferricenium ions from ferrocene in the condensed phase takes place in the presence of HCl and traces of oxygen. Ferricenium ion acts as a Lewis acid and catalyzes dehydrochlorination, crosslinking, and charring of PVC.…”

“…Its Cl (2p) XPS spectrum divides into two peaks, Cl (2p1/2) and Cl (2p3/2), with binding energies of 201.6 and 200.0 eV, respectively. 6 A new peak appears in the Cl (2p) XPS spectrum of PVC/ferrocene. The Cl electron binding energies and area percentages of the two kind of Cl atoms in PVC/ferrocene blends are listed in Table IV, indicating the presence of the above structural formula.…”