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    Author(s): Peter Koch
    Date: 1970
    Source: Forest Products Journal, Vol. 20(11): 28-31
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (793 KB)


    Plywood was made from eight loblolly pine trees selected to exhibit a range of specific gravity and growth rate. three-ply, 3/8-inch specimens were exposed outdoors for 3 years in central Louisiana; percentage of delamination was measured annually. Rings per inch and tightness of peel had minor effects. A low gluespread resulted in rapid delamination, particularly with high-density veneer or long assembly time. Of glues having a low percentage of resin solids, those extended solely with wheat flour resisted delamination. Glues extended with blood suffered more severe delamination, even when percentage of resin solids was high. High specific gravity wood delaminated more rapidly than low specific gravity wood, particularly if gluespread was low or assembly time long. Plywood given a long assembly time tended to delaminate, and dense veneer or light gluespread accelerated the effect. Rate of delamination decreased after the first year, but general conclusions about the primary variables were the same after 3 years as after 6 months. An 11-factor equation explained 35 percent of the variation in terms of wood properties and results of a standard shear test.

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    Koch, Peter. 1970. Delamination of Southern Pine plywood during three years of exterior exposure. Forest Products Journal, Vol. 20(11): 28-31

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