Wheat gluten fractions as wood adhesives—glutenins versus gliadins

Abstract

Plant proteins, such as wheat gluten, constitute attractive raw materials for sustainable wood adhesives. In this study, alkaline water dispersions of the protein classes of wheat gluten, glutenin, and gliadin were used as adhesives to bond together wood substrates of beech. The aim of the study is to measure the tensile shear strength of the wood substrates to compare the adhesive performance of glutenin and gliadin and to investigate the influence of application method and penetration of the dispersions into the wood material. A sodium hydroxide solution (0.1M) was used as dispersing and denaturing agent. Dispersions with different protein concentrations and viscosities were used, employing wheat gluten dispersions as references. Two different application methods, a press temperature of 110 C and a press time of 15 min, were employed. The tensile shear strength and water resistance of the wood substrates were compared, using a slightly modified version of the European Standard EN 204. The bond lines of the substrates were examined by optical microscopy to study the penetration and bond-line thickness. The results reveal that the adhesive properties of gliadin are inferior to that of both glutenin and wheat gluten, especially in terms of water resistance. However, the tensile shear strength and the water resistance of gliadin are significantly improved when over-penetration of the protein into the wood material is avoided, rendering the adhesive performance of gliadin equal to that of glutenin and wheat gluten. V C 2011 Wiley Periodicals, Inc. J Appl

Protein-based adhesives for particleboards

“…Specially, for the dispersions with low concentration (low viscosity) overpenetration into the wood particles can cause poor glue bonds [19]. This is in accordance with previous studies of wheat gluten as glue for solid wood [20][21].…”

Preparation and Testing of Plant Seed Meal-based Wood Adhesives

“…Due to these variation and other known and unknown factors, it is not uncommon to see large standard deviations (>10%) observed in the shear strength measurements, as in Table 1 and the literature [6][7][8]12,25 , and this may undermine some statistical analysis at P ≤ 0.05. Thus, some papers simply present the data with standard deviations, then compare and discuss them without statistical significance analysis (e.g., 7,8,12,26 ). This approach still makes some sense by showing general trends of influence from test variables.…”

“…In the past two decades, this trend has reversed with renewed interest in the use of materials that are renewable, biodegradable, and more environmentally acceptable. These natural resources include, but are not limited to, soy protein [3][4][5] , cottonseed protein 6 , rice bran 7 , wheat gluten 8 , distillers grain protein 9 , canola protein and oil [10][11][12] , lignin from sorghum and sugar cane bagasse 13,14 , and polysaccharides derived from shrimp shells 15 .…”

Wetting and film formation of wheat gluten dispersions applied to wood substrates as particle board adhesives

“…Proteins have a long tradition as adhesives for wood applications, as an example casein has been used for more than a century [1]. Another protein that has obtained significant interest in this context is wheat gluten [2][3][4][5]. Wheat gluten (WG) is a by-product from starch production and is at present mainly used in the bakery industry and as animal feed.…”