Preparation and Characterization of a Robust, High Strength, and Mildew Resistant Fully Biobased Adhesive from Agro-Industrial Wastes

Abstract

Recent decades have witnessed an increasing trend of replacing conventional formaldehyde-based adhesives with sustainable and ecofriendly biobased adhesives in the commercial wood industry. The present study developed a full biomass utilization design for adhesives consisting of a cheap soybean meal and a lignin-based crosslinking agent (EXL). The primary component of the latter, i.e., epoxidized lignin, was synthesized using alkaline lignin and epichlorohydrin under simple reaction conditions. The Fourier transform infrared, proton nuclear magnetic resonance, and carbon-13 nuclear magnetic resonance analyses revealed the epoxy characteristic peaks in EXL, further validating the efficacy of the design developed. This simple design successfully synthesized the EXL with more epoxy groups. Moreover, a fully biobased adhesive with a wet bonding strength of up to 0.96 MPa was produced by incorporating the EXL as a sole crosslinking agent, which satisfies the requirements for interior plywood use. Furthermore, the effect of the lignin-based crosslinking agent with more epoxy groups on the structural changes, thermal stability, and micromorphology of the resulting adhesive was investigated. The incorporation of EXL exhibited a beneficial impact on the soy adhesive with improved wet bonding strength and thermal stability. Additionally, the antimold observation experiment under a high humidity environment demonstrated that the EXL contributed to the excellent antimold performance of the adhesive.

An Eco-Friendly Wood Adhesive Consisting of Soybean Protein and Cardanol-Based Epoxy for Wood Based Composites

“…It indicated that 8% of CBE was too much for cross-linking soybean protein. The reactions between soybean protein and CBE will form a three-dimensional cross-linking structure, resulting in the improvement of mechanical properties and wet-cohesion of the cured CBE-modified soybean protein-based adhesives [ 25 , 26 ]. However, the residual CBE in the cured adhesive might have acted as a plasticizer to decline its mechanical properties.…”

An ionic liquid‐enhanced soy protein adhesive with high bonding strength and antibacterial activity

“…Scientists have studied a variety of bio-based adhesives, including starch, 8 soy protein, 9 cottonseed protein, 10 tannin, 11 and lignin. 12 Among these materials, soy protein is especially attractive because it is renewable, biodegradable, economical, can be obtained in high yield, and is rich in reactive functional groups. 13 However, soy protein adhesives have a number of shortcomings, including poor water resistance, low bonding strength, easy deterioration, and susceptibility to mold, all of which have large adverse effects on the durability and bonding strength of the product.…”

“…In recent years, bio‐based adhesives have attracted the attention of the research community. Scientists have studied a variety of bio‐based adhesives, including starch, 8 soy protein, 9 cottonseed protein, 10 tannin, 11 and lignin 12 . Among these materials, soy protein is especially attractive because it is renewable, biodegradable, economical, can be obtained in high yield, and is rich in reactive functional groups 13 .…”

Preparation and Characterization of Plant Protein Adhesives with Strong Bonding Strength and Water Resistance

“…Trialdehyde adhesive (urea formaldehyde resin, melamine formaldehyde resin, and phenolic resin) was widely used in the traditional wood industry [ 1 ]. However, trialdehyde adhesive had some problems, such as relying on oil resources, releasing formaldehyde, and polluting the environment [ 2 ].…”