Understanding Protein Behavior for Bio-Based Wood Adhesives and Forest Products

Photo Credit

Forest Service photo by Nayomi Plaza

Protein-based adhesive created by the Forest Products Laboratory.

Protein-based adhesives are already used in interior wood products across North America, including soy protein-based adhesives, which consume large volumes of soybeans each year. Their performance depends strongly on how the protein is structured and processed. This project focuses on the chemistry and material science of those systems: how proteins denature, coalesce, and form load-bearing networks during hot pressing, and how those changes influence dry strength, wet strength, and durability.

The central goal of this project is to improve fundamental understanding of protein adhesives. For example, rather than treating denaturation as a single “good” or “bad” event, the project examines the full pathway from raw protein materials to cured bond lines, so that scientists and industry can better predict which material characteristics lead to useful forest product applications.

Key Findings

• Protein adhesive performance depends on the interaction of temperature, moisture content, and press time during curing.
• Good wet strength of protein-based adhesives can be achieved through a cohesive protein network without relying on reactive chemistry for moisture resistance.
• Excessive protein fragmentation and high carbohydrate content can weaken bonds and lower water resistance of adhesives.
• Protein coalescence appears to occur only within a narrow processing window, showing that curing behavior is more controlled than a simple unfolding process.

Approach

Photo Credit

Forest Service photo by Nayomi Plaza

An Automated Bond Evaluation System (ABES) unit is used to test the strength of bioadhesives in veneer.

This project combines analysis of protein materials, formulation testing, and adhesive performance measurement to understand how protein properties affect bond behavior. The research looks at the bulk composition, secondary structure, molecular weight distribution, and functional characteristics of protein-containing materials left over from agricultural processing, then relates those measurements to curing behavior, rheology, and bond strength in wood products. 

A major focus of the project is how the adhesive changes during processing and how the bond forms. The team is testing how protein properties, plasticizers such as water, and hot-press temperature influence coalescence and network formation in the adhesive layer. Scientists are measuring shear strength after soaking in water, as well as characterizing the protein network to understand how proteins form stronger, more water-resistant bonds. This work is supported by funding from USDA and industry partners, including Solenis and the United Soybean Board, and is designed to help translate basic protein science into practical product specifications.

Expected Outcomes

The expected outcome is a clearer scientific basis for designing protein-based adhesive systems for forest products, including more reliable explanations of why some formulations perform well and others fail. The project will help identify which protein fractions, processing windows, and structural features are most important for dry strength, wet strength, and bond durability.

Longer term, the work is intended to support new and improved products made from U.S. agricultural commodities, expand market opportunities for farmers and processors, and strengthen domestic supply chains for bio-based materials used in forest products. It also provides industry-relevant guidance for manufacturers seeking to optimize protein-based systems already used at commercial scale.