Evaluation of wood bonding performance of water-washed cottonseed meal-based adhesives with high solid contents and low press temperatures

Authors: He, Zhongqi; Cheng, Huai

Submitted to: Journal of Adhesion Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2017
Publication Date: 8/21/2017
Citation: He, Z., Cheng, H.N. 2017. Evaluation of wood bonding performance of water-washed cottonseed meal-based adhesives with high solid contents and low press temperatures. Journal of Adhesion Science and Technology. 31(23):2620-2629

Interpretive Summary: Adhesive bonding plays an increasing role in the forest product industry and is a key factor for efficiently utilizing timber and other lignocellulosic products and resources. Recently, we prepared water-washed cottonseed meal (WCSM) on a pilot scale for promotion of its industrial application. In this work, we tested the wood bonding performance of WCSM with high solid contents and low press temperatures per industrial input. Increasing the WCSM content did not substantially change the adhesive strength but increased the viscosity of WCSM slurries dramatically. The shear strength at break of the maple wood pairs bonded at low temperatures (40 and 60 oC) was lower than that of maple pairs bonded at 100 oC. However, the shear strength of the pairs bonded at lower temperatures could be improved by extending the press time. The addition of denaturing reagents showed impacts on the adhesive strength and viscosity. Based on these observations, eight adhesive slurries were formulated and tested. These formulations could be used as the basis for developing low temperature WCSM-based wood adhesives to meet the criteria of both operational flowability and shear strength of the domestic furniture and small utensils niche markets for forest products.

Technical Abstract: Water-washed cottonseed meal (WCSM) has been shown as a promising bio-based wood adhesive. Recently, we prepared WCSM on a pilot scale for promotion of its industrial application. In this work, we tested the bonding strength of WCSM slurries with high solid contents and low press temperatures per industrial input. Increasing the WCSM content from 11% to 20% and 30% did not substantially change the adhesive strength but increased the viscosity of WCSM slurries dramatically. The shear strength at break of the maple wood pairs bonded at 40 and 60 oC was lower than that of maple pairs bonded at 100 oC. However, the shear strength of the pairs bonded at lower temperatures (40 and 60 oC) could be improved by extending the press time from 20 min to 120 min. Addition of citric acid (CA) improved the viscosity of the WCSM adhesive at 20% solid content, but lowered the adhesive strength. The addition of denaturing reagent sodium dodecyl sulfate (SDS) showed reverse impacts on the adhesive strength and viscosity, compared to CA addition. Based on these observations, eight adhesive slurries were formulated with 20 and 30% of WCSM, 3% of CA or SDS, or 9.6% or 19.1% of denaturing reagent guanidine hydrochloride (GdmCl), and their bonding strengths were tested. These formulations could be used as the basis for developing low temperature WCSM-based wood adhesives to meet the criteria of both operational flowability and shear strength of the domestic furniture and small utensils niche markets for forest products.