Flammability of Polymers (Inhibition of Flame Reactions)

Abstract

All commercial plastics will burn under the right conditions. To overcome this problem incorporation of flame retardant additives and chemical modification to the polymer have been used with varying success. These measures may affect solid phase pyrolysis of the resin or the burning of volatile fragments in the gas phase. The present research was devoted to development of methods for studying the gas phase reactions in a manner applicable to burning conditions. The performance of a range of commercial flame retardant additives was assessed in an unsaturated polyester resin system using test methods which reflect burning and ignition properties. A marked synergistic effect was noted between halogenated compounds in the presence of antimony trioxide. On heating antimony trioxide with chlorinated paraffin antimony trichloride was shown to be the chief reaction product. Weight loss experiments indicated that some mixtures should have been more effective than was observed in the early experiments. It was concluded that these test methods provided conditions of too low thermal stress and a number of resin formulations were subjected to the more severe BS.476 fire propagation test. A diffusion flame apparatus suitable for burning model fuels was set up and a number of inhibitors were studied but practical difficulties occurred in attempting to disperse metal halides quantitatively in the flame. An apparatus was designed for burning premixed model fuel/air flames to study materials such as metal halides. Antimony trihalides and a number of other metal halides were shown to be effective inhibitors. The particular efficiency of antimony trihalides was attributed to their ability to undergo oxidation providing solid particles which were effective in abstracting reactive flame species. A number of techniques have been established using known technological effects, these have been used in obtaining some new information which is applicable on a broader basis.