by Dr. Dilpreet Bajwa
Mechanical Engineering, North Dakota State University
Building products, construction and the furniture industry are the largest users of particleboards. The particleboard market grew at the rate of 6% during 2009-2016 period, reaching $17 billion in 2016. Typically, particleboard is made from wood particles, adhesive (glue) and wax. There are different types of glue that can be used to bind wood particles. The most common types of glue are fossil fuel derived, such as phenol formaldehyde, urea formaldehyde, melamine formaldehyde and methylene diphenyl diisocynate (MDI). They are widely popular as they are economical, abundant and their performance characteristics are well understood.
One of the major issues with formaldehyde types of glue is the formaldehyde emission. In 1987, the U.S. Environmental Protection Agency (EPA) classified formaldehyde as a probable human carcinogen. Formaldehyde is reported to cause allergies, asthma and reaction with skin. The 2010 Formaldehyde Emission Standard for Composite Wood Products brought formaldehyde emissions under the Title VI, Toxic Substance Control Act. Thereafter, the quest for natural, safe and reliable glue alternatives that can be used as a binder in particle boards started.
Natural feedstocks for manufacturing glues include proteins, starches, gums, plant oils and etc. Epoxidized plant oils have become popular feedstocks for manufacturing glues as they are locally available, abundant and reliable. However, some weaknesses in these glues are their performance and cost. Plant oil derived glues are expensive, susceptible to moisture and have a short shelf life, therefore, they haven’t reached their full potential. There is continuing research and development efforts to improve the quality and performance of these resins.
At North Dakota State University our group is exploring another abundant raw material, corn distillers dried grains with solubles (DDGS), a byproduct from ethanol plants as a source of natural glue and fibers in the particleboards. DDGS contains roughly 30% proteins, 13% fat and 39% fibers. The research began four years ago with funding from North Dakota Corn Utilization Council to explore the potential of DDGS as value added filler in particleboards. The results of our first study (published in Industrial Crops and Products) showed that DDGS can help to reduce the amount of glue and wax in the particleboards. This information helped us to believe that zein proteins in DDGS carry the potential to act as binders in particleboards. Since DDGS proteins are globular and inert their surface needs to be functionalized, so they can couple with wood particles. We selected sodium hydroxide (alkali), acetic acid and formic acid to treat DDGS proteins. The process of functionalizing DDGS involved micronizing DDGS to 120 and 250 micrometer particles to increase their surface area followed by acid or alkali treatment. The treated DDGS were blended with pine wood flour at 10, 25 and 50 % rate and hot pressed into particleboards.
The results of this project showed that DDGS proteins can be decoupled by acid and alkali treatments. Chemical concentration of acid and alkali influenced the flexural and internal bond strength of particleboards. Acetic acid treated DDGS at 50 weight % filler content exhibited best water resistance. Superior flexural properties of particleboards occurred when pressed at 190 °C, identical to commercial processing conditions. Test results also showed that the internal bond strength exceeded the minimum requirement by the ANSI A208.1-2009 standard. This research verified that DDGS have strong potential to act as a natural adhesive for manufacturing medium density particleboards. The results of this project led to the filling of an invention disclosure in July 2018 with NDSU Technology Transfer office. For more information please contact –