Iben Hansen-Bruhn, Aarhus University, Denmark, and University of Central Lancashire, UK
Two different ammonium phosphate based PIN flame retardants were applied to 12 mm pine plywood: vacuum impregnation of aqueous mono ammonium phosphate solution and intumescent surface coating of ammonium polyphosphate based. Both resulted in total heat release significantly lower than for untreated plywood (-34% and -20% respectively), in both cases achieving Euroclass B-s1, d0 (versus D-s2, d0 for untreated plywood). Peak smoke toxicity was however three times higher with impregnation compared to coating in under-ventilated fires (smoke from FR coated plywood was similar to untreated). The conclusion is that fire protection by intumescent PIN FRs, which generate char, can be effective in reducing heat release without significantly increasing smoke toxicity.