How Overdrying Wood Reduces Its Bonding to Phenol-Formaldehyde Adhesives: A Critical Review of the Literature. Part I. Physical Responses


  • Alfred W. Christiansen


Drying, inactivation, adhesive, bonding, review, extractives, mechanism, wettability


This review critically evaluates literature on the ways in which excessive drying (overdrying) inactivates wood surfaces to bonding, primarily for phenolic adhesives. In Part I of a two-part review, three inactivation mechanisms involving physical responses to overdrying are considered: (1) exudation of extractives to the surface, which lowers the wettability or hides the surface; (2) reorientation of wood surface molecules, which reduces wettability or places for bonding; and (3) irreversible closure of large micropores in cell walls. I believe that extensive evidence from wood bonding and paper sizing research supports the mechanism of extractives-induced low wettability as the cause for inactivation of Douglas-fir and southern pines. Molecular reorientation and irreversible micropore closure are proposed wood inactivation mechanisms that involve loss of wettability and bonding sites.


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