Progress 05/15/04 to 03/31/05
Existing wood adhesives are derived from synthetic, petroleum-based materials. These products often contain volatile organics (VOCs) and other toxic chemicals. As wood adhesives, bacterial exopolymers distinguish themselves from all other products through their synthesis using renewable agricultural products, the absence of VOCs and other toxic chemicals, and favorable costs of production. Replacement of VOC-and other toxic chemical-containing synthetic wood adhesives will: 1) reduce the need for cabinet makers and other wood crafters to construct and maintain expensive ventilation systems to protect workers from VOC vapor intoxication, 2) reduce worker exposure in manufacturing plants to toxic materials, 3) eliminate the generation of toxic waste products, 4) provide health benefits to consumers with chemical sensitivities, and 5) create a new market for agricultural feedstocks. The Phase I SBIR project had 5 major goals: identification of optimal EPS composition,
formulation optimization, development of application methods and use parameters, evaluation of plywood applicability, and improving moisture resistance. We have substantially met all of these goals, and developed a series of commercially viable EPS adhesives. Shear strengths associated with maple wood bonding applications have exceeded 3,000 psi (wood failure) for the SBC adhesive. In a study of the setting rate (shear strength vs. time) of the SBC adhesive, maximum shear strength at either 23 or 53 % relative humidity (RH) was reached at 2 days while half of maximum strength was reached at 2 h. Finally, we instituted a molecular modeling program to explore the mechanism of interaction between wood surfaces and extracellular polysaccharide adhesives of microbial origin. The goal of the modeling effort is to improve EPS adhesive performance by developing a more robust theoretical framework that can better describe the fundamental mechanisms by which EPS interacts with wood and other
materials of interest. Specific objectives that were addressed in the modeling program at SBC included 1) predictions of which EPS adhesives interact most strongly with modeled wood surfaces, 2) describe the fundamental chemical mechanism(s) by which EPS adhesion to modeled wood surfaces takes place, and 3) determine the relationship between the type of EPS derivatization (e.g., acetylation, succinylation, etc.) and the theoretical water resistance of the adhesive bond. Overall, the performance of EPS-I meets many requirements of a wood adhesive but is lacking primarily in moisture resistance. In its present form, it may be suitable for interior, non-structural applications. Preliminary results with new, related compositions have shown the ability to improve moisture resistance by structural modification of the base polymer. Considering the compelling need for wood adhesives which are non-hazardous and based on renewable resources, continued research on improved EPS materials for this
application is justified.
For the first time, a microbially-produced extracellular polymer has been developed as a wood products adhesive. Many of the properties associated with this adhesive are similar to those of currently marketed products. The Specialty Biopolymers Corporation adhesive is effective, environmentally friendly, biodegradable, and produced from renewable resources. As such, this adhesive should serve as a prototype for future "green" adhesive products. We have had substantive discussions with a number of potential customers for our biologically-derived adhesives. The feedback from these discussions has been very positive, and has resulted in changes to the formulation chemistry to meet the specific requirements of particular applications. We have provided samples of various adhesive formulations to a number of small and large adhesive consumers. SBC has developed formal collaborations with two companies in the fine arts manufacturing business: both companies have very
specialized applications for our adhesives, and have found the products to be far superior to products currently marketed for their manufacturing operations.
- Haag, A.P., G.G. Geesey, and M.W. Mittelman. 2005. Bacterially derived wood adhesive. Int. J. Adhesion Adhesives (accepted 2/05).
- Geesey, G.G., M.W. Mittelman, A.P. Haag, and H. Ridgway. 2005. Wood adhesive derived from bacterial extracellular polysaccharides. Abst. Ann. Meet. Adhesion Soc. Am., February 13-16, Mobile, AL