Strategies for improving the performance of plywood adhesive mix fillers from southern yellow pine bark
Southern yellow pine bark was obtained from an industrial source and subjected to grinding and classification operations to ultimately afford finely ground bark fractions for evaluation as plywood adhesive mix fillers. Specifically, by grinding in a laboratory blender, we were able to generate a bark fraction rich in periderm tissue with its interlocking spiculate stone cells (sclereids). Another significant bark fraction was comprised of cellular debris from the obliterated phloem tissues in bark that are partitioned by the periderms. Through the grinding and classification operations employed in this study, the filler rich in periderm tissue had superior performance ( 90% wood failures) over both the filler rich in obliterated phloem tissue and that prepared directly from the bark as received. This appears to be related to the removal of extractive-rich bark components that likely promote resin undercure. The periderm-rich filler had the added benefit of an ash content (2.5%) that was significantly lower than that for the whole bark filler (9.4%).