The Effects of Green Veneer Water Content, Dryer Schedules, and Wettability on Gluing Results for Southern Pine Veneer

Southern pine veneer dried by two appreciably different production schedules was evaluated for glue bond quality in relationship to: 1) water content of green veneer, 2) surface wettability by water drop absorption of adjacent unsanded (U) and sanded (S) springwood, and 3) unsanded vs. lightly sanded plywood panel interfaces. There were no differences in U or S values or in wet shear values between dryer schedules. Wood failure results were 84 vs. 64 percent for unsanded veneer and 88 vs. 72 percent for sanded veneer, for schedules 1 and 2, respectively. Decreasing wood failure was highly associated with decreasing wettability and decreasing water content. There was no quantitative relationship between U, U-S, and wood failure results or surface inactivation. Wet shear values did not decrease as surface inactivation or U-S values increased. Surface inactivation and poor wettability due to overdrying of low water content veneer were more detrimental to good adhesion than high permeability; panels of sanded veneer had superior wood failure results, especially for schedule 1.

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