Research And Development Of Novel Formaldehyde Free Wood Adhesives From Biomass

The plywood paneling and furniture industry consume millions of tons of adhesives each year. Current industrial wood adhesives are made solely from petroleum and natural gas. They contain many environmental- and health-hazardous chemicals such as formaldehyde. The goal of our research was to develop biodegradable and formaldehyde-free wood adhesives. The specific objectives of the present thesis were to develop processes to make formaldehyde-free wood adhesives from soy flour and corn starch, and to evaluate these biobased wood adhesives under different conditions. Some important chemical and physical aspects of the ingredients, reactions and products were studied in order to understand the fundamentals underlying the processes and product properties. Such understanding of the fundamentals is critical to the design and control of the processes and products.1.Research and Development of Soy Protein-based Formaldehyde-free Water Resistant Wood Adhesive.The conventional soy protein-based adhesives production processes use a large amount of alkali for soy globulin denaturation. The use of excess alkali often results in poor water resistance, short pot-life, alkali-induced stain in the plywood, and short shelf life. In this study, a two-step process, which includes a denaturation step and a homogenization step, was developed to produce formaldehyde-free water resistant wood adhesives from soy flour using significantly less alkali.1.1. Effect of Alkali (Sodium Hydroxide) on Soy Protein DenaturationOur research showed that proper alkaline denaturation of soy globulin increased the viscosity and adhesiveness of the products probably due to the protein unfolding and increased number of active hydrosulfide groups in the product. However, excessive use of alkali would increase the residual alkali in the products, causing deamination of basic amino acid and hydrolysis of the peptide linkages, which would gradually reduce bonding strength of the adhesives. Therefore it is important to control the alkali used in soy globulin denaturation. It was found that for the ratio of liquid denaturant to dry mass of soy flour of 1.25, the alkali concentration (expressed as gram sodium hydroxide / gram dry mass of soy flour, w/w) should be controlled within 2.25%-3.0% in order to stabilize the water resistance of the soy adhesive.1.2. Effect of Urea-alkali Combination on Soy Globulin Denaturant...