Resin Distribution in Hardboard: Evaluated by Internal Bond Strength and Fluorescence Microscopy

J. A. Youngquist, G. C. Myers, L. L. Murmanis


Product performance, to a large extent, depends upon the uniformity of resin deposition on or through the hardboard product. Presently, destructive testing of the hardboard, by measuring its internal bond (IB) strength, is the only method that will provide information about adhesive bond performance.

The objective of our research was to compare IB test results with resin distribution patterns observed by microscopy of wet- and dry-formed medium- and high-density hardboards formed under varying conditions of pre- and post-blending variables.

Using fluorescence microscopical techniques, we found that differences in resin distribution can be clearly detected. We observed that decreasing the resin solids content, mechanically increasing the fiber rubbing action with the resin, and changing the rate of resin application were effective ways for improving resin distribution in hardboard furnish. Our microscopic technique also showed that uniform distribution of the resin throughout the hardboard produced boards with the highest IB strengths.

This research provides guidelines for estimating levels of IB strength based on the use of a developed fluorescence microscopical technique.


Resin;distribution;hardboard;internal bond;microscopy

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