A Novel Application of Silicone-Based Flame-Retardant Adhesive in Plywood
Mauro Zammarano, John R. Shields, Elizabeth D. Knowlton, Ickchan Kim, Matthew S. Hoehler
A silicone-based elastomer filled with vinyl-silane treated aluminum hydroxide was used as a flame- retardant adhesive for plywood, as a replacement for a conventional polyurethane-based adhesive. The shear strength and fire performance of such a silicone glued plywood (SI/plywood) were investigated and compared to those of the polyurethane-based adhesive glued plywood (PU/plywood). Shear strength tests showed that the shear strength of SI/plywood [(0.92 ± 0.09) MPa] was lower, but less sensitive to hot-water immersion (63 oC for 3 h, 62 % reduction for the PU/plywood and 30 % reduction for the SI/plywood), as compared to the PU/plywood. The fire performance of plywood was assessed by a simulated match-flame ignition test (Mydrin test), Lateral Ignition and Flame Spread Test, cone calorimetry, and thermocouple measurements. The results showed that the SI/plywood exhibited an obvious improvement in terms of ignition, burn-through, flame-spread, heat release rate, and thermal barrier efficiency as compared to the PU/plywood. The silicone-based adhesive generated an inorganic protective layer on the sample surface that visibly suppressed glowing and smoldering of the plywood during combustion. The silicone-based adhesive was also combined and reinforced with cellulosic fabric (CF) or glass fabric (GF) to prepare composite plywood (SI/CF/plywood and SI/GF/plywood) with improved fire performance. Cone calorimetry indicated that the use of CF or GF in SI/CF/plywood and SI/GF/plywood, respectively, suppressed the delamination of composite plywood and promoted the formation of an effective thermal barrier during combustion. Particularly, the composite plywood containing GF exhibited the most effective fire barrier and the lowest heat release rate among the plywood types investigated in this study.