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Douglas-fir or southern yellow pine? Why choose?


By Audrey Zink-Sharp

March 18, 2014 – Research being conducted by Kyle Mirabile, Elizabeth Parcell Sharp, Scott Renneckar, and Audrey Zink-Sharp is shedding some light on what features of Douglas-fir versus southern yellow pine are likely leading to the inability of certain adhesives to qualify for use in structural applications that must withstand cyclic moisture conditions. Douglas-fir and southern yellow pine are two of the most widely used woods for structural applications and specialty composites, yet a lack of fundamental knowledge has limited improvement of adhesives that can work equally well on both wood types. The research is sponsored by the Wood-based Composites (WBC ) Center and includes Henkel, Momentive, Georgia-Pacific Chemicals, and Ashland as technical partners. 

This past summer, southern yellow pine trees (Pinus taeda) were harvested from the Reynolds Homestead Forest in Critz, VA. In late December, 2013, WBC colleagues at Oregon State University assisted with harvest and transport of Douglas-fir logs to Blacksburg. Boards were sawn from the logs using our department’s portable sawmill and then dried in the kiln. Various and numerous (!) specimens have been prepared from each tree type and are awaiting further processing.

   

Kyle Mirablile at the microtome Kyle Mirablile at the microtome

Currently underway are analyses of cellular anatomy, wood density, surface wettability, and chemical composition. Very soon, bonded assemblies will be constructed and tested for bond strength, bond durability, bondline thickness, adhesive penetration, and dimensional stability while enduring cyclic moisture fluctuations. Exploration of bondline chemistry with 2D and 3D mapping is also planned. 

Results from the project could lead to adhesive formulations that meet qualification requirements when the adhesives are applied to either Douglas-fir or southern yellow pine composites destined for structural laminated wood products located in exterior exposure situations. New formulations that function equally well with either wood type likely will decrease production cost, improve production efficiency, and enhance composite performance. Kyle Mirablile at the microtome.


 

   

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