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Forest Service Researchers Develop Water-Resistant Soy-Based Wood Adhesive

North America's annual consumption of petroleum-based phenol formaldehyde adhesive resins for composite wood panels is forecast to grow more than 20% in the next seven years from 4.4 million pounds currently, which is valued at $2.82 billion, according to the Iowa Soybean Promotion Board.

The challenge for researchers from the laboratory — who were collaborating with Heartland Resource Technologies of Oelwein, IA — was to formulate a product with better water resistance than the soy-based glues that became popular in the early 20th century for plywood panels. Those products failed when wet, so their use was limited to internal applications.

Researchers developed several formulations of soy and phenol hybrid adhesives and used them in the face section of strandboard. To test how well the sample glues would hold up, boards were immersed in water for 24 hours and boiled for two hours. The adhesive that successfully emerged from these trials is three-fourths soy, with the remainder composed of phenol and natural gas-based formaldehyde.

Researchers say that their product is not only durable, performing equally well as those manufactured today, but it can be made through a process that is very similar to what manufacturers are already using. It has been successfully demonstrated in oriented strand board, particleboard, plywood and molded products.

The prototype product is good for the environment, according to James Wescott, chief operations and technical officer at Heartland, because it contains less petroleum and maximizes the use of soy, which is grown and harvested primarily for its oil. The glue is made up of the flour, or soy meal, that remains after the oil is extracted, and that product is currently used mostly as animal feed.

Heartland projects it will be using as much as one million bushels of soybeans annually for soy adhesives by their fifth year of production.

The research on the soy glue was conducted under the Cooperative Research and Development Agreement (CRADA).

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