Submitted to: Industrial Crops and Products
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2013
Publication Date: 1/3/2014
Citation: Holt, G.A., Chow, P., Wanjura, J.D., Pelletier, M.G., Wedegaertner, T. 2014. Evaluation of thermal treatments to improve physical and mechanical properties of bio-composites made from cotton byproducts and other agricultural fibers. Industrial Crops and Products. 52:627-632. Interpretive Summary: Previous studies evaluating waste material from cotton gins, known as cotton burs, as a wood replacement for use in composites such as particleboard, revealed high water absorption rates compared to wood. A review of the literature showed numerous studies where agricultural residues/fibers were treated chemically or with heat (thermally) to minimize the water absorption properties of the material. This study evaluated three heat treatment methods on pressboards made from cotton burs, cotton stalks, kenaf, flax, and southern yellow pine. Boards were also made from 50/50 blends of cotton burs and the other agricultural fibers. Results showed the 100% cotton bur board had improved water resistance as a result of the heat -treatment and performed comparable to the pine board. The board made from 50% cotton bur and 50% pine perfomed equivalent to the 100% pine board. The cotton bur composite that had the best overall performance was the 50% blend with flax which has significantly lower water absorption than any of the pine composites. Overall, results showed that cotton burs can be used successfully in blended composites.
Technical Abstract: Demand for wood products continues to grow at levels that challenge the available resources. Alternative materials are sought to sustainably supplement the wood fiber industry. Experiments were conducted on composite boards made from agricultural residues. The boards were subjected to thermal treatments to improve mechanical properties. Board construction was accomplished by pressing fibers in a 10% resin matrix with 1.5% wax at 166°C and 3.45MPa. Composite boards were produced using cotton carpel, cotton stalks, kenaf, flax, and southern yellow pine, and cotton carpel blended 50%/50% with kenaf, cotton stalks, flax and southern yellow pine. In one thermal treatment, fiber was heated to 185C for 30 min. before the boards were made. In the other thermal treatment, finished boards were heated to 185°C for 30 min. Four specimens from each board were subjected to water absorption, thickness swelling, internal bond, and stress testing modulus of rupture and modulus of elasticity in accordance with methods described in the American Society for Testing and Materials (ASTM) D 1037-06a. Thermal-treating the fibers post-fabrication reduced water absorption in all boards compared to untreated specimens. Thermal-treating had mixed effects on MOE, MOR, and internal bond with some fiber composites having improved values while others had lower values. Kenaf had significantly higher water absorption and swell properties compared to the other materials. Southern yellow pine and flax had equivalent water resistance. Composite blends with cotton carpel exhibited equal or improved mechanical properties compared to non-blended treatments.