Soy Proteins as Wood Adhesives

Protein-based adhesives have a long and ingenious history. Animal protein, casein from milk, soy flour, and even blood have historically been used as bonding agents for wood product applications. These proteins have allowed for the development of bonded wood products such as plywood and glued-laminated timbers in the early 20th century.


Casein proteins from milk were used to make glued-laminated arches, seen here in the construction of the former Building Two at FPL (1930s).

Petrochemical-based adhesives replaced proteins in most wood bonding applications because of lower cost, improved production efficiencies, and enhanced durability. Technological and environmental factors, however, have led to a resurgence of proteins, especially soy flour, as an important adhesive for interior nonstructural wood products. Among other factors, more stringent regulations limiting formaldehyde emissions from composite and wood panels have driven renewed interest in soy adhesive technology.

Charles Frihart and Christopher G. Hunt, both Forest Biopolymer Science and Engineering chemists at FPL, along with co-author Michael Birkeland, of AgriChemical Technologies, describe the value of soy proteins as wood adhesives in a chapter of Recent Advances in Adhesion Science and Technology (Gutowski & Dodiuk, eds.).

Their paper discusses important aspects of protein structure and recent successful advances in higher performance soy flour adhesives for wood bonding. Protein wood adhesives have recently displaced fossil fuel-based adhesives in some markets and have the potential to replace a significant percentage of fossil fuel-based wood adhesives worldwide.