Bond quality of phenol-based adhesives containing liquefied creosote-treated wood
Liquefaction of spent creosote-treated wood was studied to determine the technological practicability of its application in converting treated wood waste into resin adhesives. A total of 144 plywood panels were fabricated with experimental variables included 2 phenol to wood (P/W) ratios in liquefaction, 6 resin formulations (3 formaldehyde/liquefied wood (F/LW) ratios × 2 replications), 6 glue applications (2 glue spreads × 3 assembly times), and 2 panel replications. Average shear strength (235.6 psi) and wood failure (70.5%) for resin adhesives prepared from liquefied wood at P/W ratio of 2.0 were significantly higher than the shear strength (184.7 psi) and wood failure (53.1%) for that at P/W ratio of 1.5. On average, F/LW ratio of 2.25 yielded substantially lower shear strength and wood failure than that of F/LW ratios of 2.0 and 1.75. Differences in shear strength and wood failure between F/LW ratios of 2.0 and 1.75 were not significant. However, it is interesting to note that F/LW ratio interacted with P/W ratio to affect wood failure, but not shear strength. As shown in Fig. 2, at P/W ratio of 1.5, the F/LW ratio of 2.0 yielded the highest wood failure and the F/LW ratio of 2.25 resulted in the lowest wood failure. On the contrary, at P/W ratio of 2.0, the F/LW ratio of 2.25 resulted in highest wood failure and the F/LW ratio of 2.0 yielded the lowest wood failure. On the basis of wood failure, the resins prepared from liquefied wood at P/W ratio of 2., reacted at F/LW ratio of 2.25, and applied the glue at the rate of 90 pounds per 1000 square ft of double glue line met the standard of vacuum pressure soak cycle for exterior glueline (PS-1-66). Nevertheless, the first attempt to formulate a phenol-based adhesive made from liquefied creosote-treated wood produced encouraging results. With additional studies of resole formation and glue mix formulations, it is anticipated that a resin adhesive from liquefied creosote-treated wood with improved bond quality can be developed.