Davis-Standard: Woodtruder update

The program for the Coast Guard involves the development of a new decking material and retaining wall system as a replacement for pressure treated wood. The AEWC Center recently developed a 5/4-inch by 6-inch decking product installed at one Coast Guard pier and is now working on the retaining wall. A project being funded by a USDA wood utilization research grant is evaluating post die process conditions to determine how cooling rates impact product development. A second USDA funded project deals with the formulation of nylon wood composites. This project is in its infancy with the intention of product development for automotive-type applications. Proprietary work for private companies involves development using a variety of non-wood composites, additives and formulations.
“Our clients have been very pleased with the Woodtruder’s capabilities and performance,” said Doug Gardner, professor of wood science at the University of Maine. “We’ve had even more contracted research than we had originally anticipated, which has been beneficial. The machine has also been an excellent tool for expanding our curriculum and giving students hands-on experience with wood-fiber technology.”
The Woodtruder’s processing range is made possible by its unique tandem extrusion arrangement consisting of a primary 28:1 parallel twin screw extruder and mounted single screw, side-injection extruder. The first section of the primary extruder utilizes a heating and vacuum venting system to eliminate moisture and volatiles from the wood fiber. The side-injection extruder, mounted midway through the primary extruder, separately heats and mixes the desired polymers. Depending on the wood fiber-to-polymer ratio, the polymers are then injected into the primary extruder homogenizing the mixture. Since the polymer joins the fiber in a molten state, it encapsulates the wood fibers, resulting in a thoroughly mixed, high quality composite of up to 60 percent wood fiber.
This set-up enables the AEWC Center to process a wide range of fibers including sawdust, wood (both hard and soft woods), sisal, rice husks, flax, peanut shells, recycled car tires and others, while eliminating expensive wood drying equipment. These materials can be combined with a variety of basic polymers including polypropylene, polystyrene, High-Density Polyethylene (HDPE) and Poly Vinyl Chloride (PVC), which are found in many consumer goods such as milk jugs, house siding and plumbing materials. The Center is also examining wood fiber processes using engineering thermoplastics.
“The expertise of our researchers, our modern facility, and the capabilities of the Woodtruder make it possible for us to investigate and determine the best fiber-polymer combinations for any given application,” added Gardner. “Our Center is fully equipped for prototype development. Each new material produced by the Woodtruder undergoes strenuous evaluation, like being repeatedly stressed to evaluate durability and being exposed to the equivalent of years of ultraviolet radiation, moisture and freeze-thaw cycles.”
For more information about the research and development capabilities at the AEWC Center at the University of Maine, contact Doug Gardner at (207) 581-2846 or at [email protected] For more information about Davis-Standard’s Woodtruder, contact Wendell Whipple at [email protected]

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