Submitted to: Journal of Adhesion Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2012
Publication Date: 6/3/2012
Citation: Hojillaevangelist, M.P. 2013. Evaluation of corn germ meal as extender in plywood adhesive. Journal of Adhesion Science and Technology. DOI:10.1080/01694243.2012.696958.
Interpretive Summary: We used corn germ meal as extender in sprayline glues for plywood and developed a formulation that will serve as alternative glue for plywood manufacturers. About 5 million kg (10.6 million pounds) of corn germ meal can potentially be consumed per year in the production of this adhesive, thus generating additional income to corn growers in the United States. Glues from vegetable and animal proteins were used in wood products more than a century ago, but they were eventually replaced by cheaper, petrochemical-based synthetic resin adhesives after the Second World War. However, the wood products industry has maintained its interest in these natural glues to minimize disruptions in production during periods when high petroleum prices correspondingly raised resin prices and limited its supply. Our laboratory was previously successful in developing foamed plywood adhesive that used soybean flour. In the present study, we focused on corn germ meal and evaluated its performance as protein extender in plywood glues. Corn germ meal has substantial protein (about 24%) and is made up of protein groups that have excellent functional properties. We selected plywood glue intended for sprayline coaters or roll coaters as the media for testing its effectiveness as extender. These types of glue are more tolerant of non-protein components of the extender, like oil, than other plywood glues. We substituted the corn germ meal for the standard extender in the industry glue (wheat flour) on a protein content basis; that is, the amount of corn germ meal provided the same amount of protein as that contributed by wheat flour in the standard glue mix. We found that the corn germ-based glue had satisfactory mixing properties and produced equally strong bonds as the industry standard glue. Our results indicated that corn germ meal has strong potential to be an alternative protein extender in plywood glues for sprayline coater.
Technical Abstract: This study was conducted to evaluate the potential of corn germ meal as protein extender in plywood adhesive. Partially defatted dried corn germ, containing 2.1% (dry basis, db) crude oil and 24.7% (db) crude protein, was ground to 40-mesh particle size. The corn germ meal was then substituted (on protein content basis) for wheat flour in the standard glue mix for sprayline glue. Mixing and adhesion properties of the corn germ-based glue were compared with those of the industry standard glue. The glue containing corn germ meal showed satisfactory mixing performance and had a final viscosity (2400 cP) that was almost identical to that of the standard glue (2300 cP). The mean tensile strength of the corn germ-based glue (195 psi) was likewise close to that obtained for the standard glue (201 psi) and to the threshold value of 200 psi considered as indicator of strong bonding. These results indicated that corn germ meal has strong potential to be an alternative protein extender in plywood glues for sprayline coater.