Toxic gas and smoke measurement with the British Fire Propagation test. III: UPTV formulations with reduced HCl evolution

A range of basic fillers has been incorporated into UPVC formulations and assessed for effectiveness in suppressing HCl evolution and influence on other fire properties. Investigations were carried out with the British Fire Propagation test (BS 476 Part 6) in a room previously used for assessing the fire behaviour of UPVC building products. HCl evolution was also studied following degradation in a pyrolysis tube furnace. Despite notable differences in these methods of assessment, good correlation was found between them. Varying degrees of HCl suppression were obtained and for formulations containing stronger bases effectiveness was found between them. Varying degrees of HCl suppression were obtained and for formulations containing stronger bases effectiveness was approximately stoichiometric to the amount of base present. Lithium hydroxide was thus the most effective HCl absorber on a weight basis. A formulation with 40 parts per hundred resin of this filler evolved only 2% of its theoretical HCl, although at the expense of increased fire propagation indexes. Smoke properties were not greatly influenced by the formulations. Precipitated calcite was considered the most promising acid‐absorbing filler for practical use. At 40 parts per hundred resin it reduced HCl evolution to 34% of theoretical and markedly delayed the onset of incapacitating HCl concentrations in the room, with little influence on fire propagation properties of the UPVC.