2007 Research Highlights

Research Area:
Strategic Goal: 1
SPA: Fire

Enhanced the performance of wood flour and fiber filled-plastic composites (WPCs) against moisture, decay, and termites through chemical modification.

Key Contact: Rebecca Ibach ribach@fs.fed.us
Partner: Teel-Global Resource Technologies, Harrison Experimental Forest, Saucier, Mississippi

Although laboratory evaluations of wood-plastic composites (WPCs) are helpful in predicting long term durability, field studies are needed to verify the overall long term durability. Field exposure can encompass numerous degradations i.e. fungal, UV light, moisture, wind, temperature, freeze/thaw, wet/dry cycling, termites, mold, etc. that traditionally are studied separately in the laboratory. Moisture sorption of WPCs is slower than in unmodified solid wood, but it affects the strength, stiffness, and ultimately the decay of the material.

The objectives of this study were to: 1) investigate several methods of reducing moisture sorption and, consequently, fungal degradation, 2) compare the effects of moisture and fungal decay on wood-flour-filled and wood-fiber-reinforced HDPE, and 3) perform laboratory and field evaluations of WPCs specimens. The methods used to reduce moisture were: 1) acetylation of the wood component and 2) use of a coupling agent. Acetylating wood esterifies the hydroxyl groups, making the wood more hydrophobic, dimensionally stable, and biologically durable. Coupling agents are known to promote bonding between the plastic and unmodified wood fibers when added to WPCs and have been shown to reduce moisture.

Acetylating the wood component in WPCs reduced moisture sorption and related performance losses such as decay and flexural property loss in laboratory tests. Reduction in moisture sorption and decay with addition of coupling agent were significant but not as large as acetylation. Early findings in field tests were consistent with laboratory results but considerably more time is needed to adequately assess the different formulations.