FLAMMABILITY CHARACTERISTICS OF WATER-BASED POLYCRYLIC AND OIL-BASED POLYURETHANE COATED OAK VENEER PLYWOOD SAMPLES SUBJECTED TO INCIDENT HEAT FLUXES
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The flammability characteristics of oak veneer plywood were evaluated in the Cone Calorimeter. Samples of 6.35 mm (1/4 in.) thick and 19.05 mm (3/4 in.) thick oak veneer plywood were coated with 3, 6, and 9 coats of either oil-based polyurethane or water-based polycrylic clear finishes and tested at incident heat fluxes of 35, 50, and 75 kW/m2 along with uncoated samples. Both the type of finish and the number of coatings were found to influence the ignition time, the measured peak heat release rate, and the minimum flux for ignition of the samples. The ignition times for the coated samples were 2 to 3 times lower than the unfinished samples. Predicted times to ignition differed by a factor of 2 to 3 from the measured values (with the exception of the samples with nine coats of finish.) The predicted ignition temperatures differed by as much as 100 ºC from the measured temperatures. The Quintiere flammability parameter, b, was found to be positive for all testing scenarios, suggesting a propensity for flame spread at the incident heat fluxes evaluated.