Red oak flakeboard

Figure 2. Red oak flakeboard with Desmodur PU-1520A 20 binder.

Renewed interest in bark particleboard was evidenced by a short article written by Murphey and Rishel (39). They reported results of preliminary studies on relative strengths of various bark species compared to aspen flakeboard. Bark species included aspen, black locust, green oak, white pine, oak and locust, poplar, red oak, and mixed oak. Overlaying was suggested as a means of increasing bending strengths. 

In three-layer flakeboards based on five softwood and hardwood species of 4, 10, and 18% moisture content, with press temperature of 177 °C, 6-min press time, and 3% isocyanate binder, the results showed that moisture content of wood was the most important variable at 18% moisture level, IB and bonding properties were lowest. Species of wood influenced strongly the bonding efficiency. In almost all cases the bending properties were the key characteristic of the panel performance. Southern pine produced the boards with lowest IB (81-116 psi), and red oak gave the highest IB values (98-213 psi) (J95). 

The wood raw material used was red oak flakes. Red oak, an abundant species in the North Central United States, is a relatively dense hardwood, known to be rather difficult to bind. The ultimate goal was the development of a roof decking panel which required a 1-1/8 inch (29mm) board, considerably thicker than typical flakeboard products. An exterior grade binder had to be used but conventional aqueous phenolics are relatively slow curing resins. Polymeric MDI was evaluated in an attempt to achieve the necessary exterior durability without the excessively long press times otherwise needed for curing such thick boards. 

We wish to thank Dr. Darrell D. Nicholas, Mr. Roy D. Adams and Ms. Susan Mateer of the Institute of Wood Research at Michigan Technological University for their work in conducting the mixed hardwood flakeboard experimental program. We also wish to thank Dr. Michael 0. Hunt of Purdue University and Dr. William F. Lehmann of Weyerhaeuser Corporation for their help in the red oak flake-board work and Mr. Otto G. Udvardy of Borden Chemical for the aspen waferboard study. Finally, we would like to thank Dr. Ronald Taylor of Mobay Chemical Corporation for his considerable advice and help with the multiple correlation analysis. 

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