Preparation and Testing of Plant Seed Meal-based Wood Adhesives
Summary
To facilitate the effort in seeking more economic and environment-friendly formulations of natural product-based wood adhesives, this work demonstrates the preparation and testing of plant seed-based wood adhesives. This protocol allows one to assess plant seed-based agricultural products as suitable candidates for the substitution of synthetic-based wood adhesives.
Abstract
Recently, the interest in plant seed meal-based products as wood adhesives has steadily increased, as these plant raw materials are considered renewable and environment-friendly. These natural products may serve as alternatives to petroleum-based adhesives to ease environmental and sustainability concerns. This work demonstrates the preparation and testing of the plant seed-based wood adhesives using cottonseed and soy meal as raw materials. In addition to untreated meals, water washed meals and protein isolates are prepared and tested. Adhesive slurries are prepared by mixing a freeze-dried meal product with deionized water (3:25 w/w) for 2 hr. Each adhesive preparation is applied to one end of 2 wood veneer strips using a brush. The tacky adhesive coated areas of the wood veneer strips are lapped and glued by hot-pressing. Adhesive strength is reported as the shear strength of the bonded wood specimen at break. Water resistance of the adhesives is measured by the change in shear strength of the bonded wood specimens at break after water soaking. This protocol allows one to assess plant seed-based agricultural products as suitable candidates for substitution of synthetic-based wood adhesives. Adjustments to the adhesive formulation with or without additives and bonding conditions could optimize their adhesive properties for various practical applications.
Introduction
Adhesive bonding of wood plays an increasing role in the forest product industry and is a key factor for efficiently utilizing timber resources1. Interest in the use of natural product-based adhesives for wood increased steadily from the 1930s to reach a peak around 19602. After this period, the price of petroleum-based adhesives became so low that they displaced protein adhesives from several traditional markets. 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 protein3-5, cottonseed protein6, rice bran7, wheat gluten8, distillers grain protein9, canola protein and oil10-12, lignin from sorghum and sugar cane bagasse13,14, and polysaccharides derived from shrimp shells15.
Whereas seed protein isolates have been widely evaluated as potential wood adhesives, the isolation procedure involves corrosive alkaline and acidic reagents and it makes isolate-based adhesives relatively expensive and less environment-friendly16. Thus, some defatted seed meals (flours) with or without treatment have also been tested for the adhesive purpose, even though the adhesive properties of these meals do not perform as well as protein isolates17-19. We have sequentially fractionated cottonseed meal (CM) into different fractions, and examined their adhesive strength in bonding wood veneers20,21. The water-insoluble solid fraction (hereinafter washed cottonseed meal-WCM) could be used as wood adhesives, comparable to cottonseed protein isolate (CSPI), and would be less costly to prepare than CSPI.
Adhesive strength and water resistance are two critical parameters in evaluating the performance of a potential adhesive material. Here, the adhesive strength is reported as the shear strength at break of the lap bond of each wood specimen. Water resistance of the adhesive is measured by the change in lap shear strength of the bonded wood specimen at break due to water soaking. Using defatted cottonseed and soy meals as raw materials, this protocol provides a simple and straightforward way to prepare and test plant seed-based products as wood adhesives. This protocol would be helpful in facilitating the effort in seeking more economic and environment-friendly formulations of natural product-based wood adhesives.
Protocol
Representative Results
Discussion
This paper presents a basic procedure to prepare and test plant seed-based products as wood adhesives. The adhesive slurries exampled in this protocol are simply the defatted seed meal product and water. Various adhesive formulations can be reached by addition of testing reagents (such as sodium dodecyl sulfate, sodium bisulfite or tung oil)5,6,23 and/or changes in mixing conditions (such as pH, ratio of solid and water)3,24,25. Adjustment of the adhesive formulation is also needed if the rheologica…
Divulgations
The authors have nothing to disclose.
Acknowledgements
Data reported in this work are part of the USDA-ARS National Program 306 Project ‘Values-Added Products from Cottonseed’ research supported by the Agency’s in-house funding. Publication of this paper is supported in part by the Journal of Visualized Experiments. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer. We acknowledge the constructive comments from JoVE science editor and peer reviewers in the review and revision process.
Materials
| Material and Equipment | Supplier/Manufacturer | Address | |
| defatted cottonseed meal | Kentwood Co-op | Kentwood, LA, USA | |
| defatted soy meal | Kentwood Co-op | Kentwood, LA, USA | |
| wood veneers | Certainly Wood, Inc. | East Aurora, NY, USA | |
| cyclone sample mill (model 3010-014) | UDY Corporation | Fort Collins, CO, USA | |
| Benchtop Heated Press (Model 3856) | Carver, Inc. | Wabash, IN. USA | |
| Materials Tester | Zwick GmbH & Co. | Ulm, Germany |
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