A Tough, Water-Resistant, High Bond Strength Adhesive Derived from Soybean Meal and Flexible Hyper-Branched Aminated Starch

Abstract

Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving crosslinking density is generally accompanied by a toughness reduction of the adhesive. Herein, we developed a flexible long-chain starch with a hyper-branched structure (HD), and incorporated it with SM and a crosslinking agent to prepare a novel SM adhesive. Results showed that this adhesive exhibited both excellent water resistance and enhanced toughness. The wet bond strength of plywood fabricated using this adhesive was 354.5% higher than that of SM adhesive. These achievements are because introducing HD with hyper-branched groups enhanced crosslinking density, while HD’s flexible long-chain structure improved toughness of the adhesive. This HD can promote the development of tough and hydrophobic bio-based composites.

Improving Bond Performance and Reducing Cross-Linker Dosage of Soy Protein Adhesive via Hyper-Branched and Organic–Inorganic Hybrid Structures

“…Among the chemical methods, cross-linking is preferred by most researchers [ 15 ]. Effective cross-linking agents include triglycidylamine [ 16 ], polyamidoamine-epichlorohydrin [ 17 , 18 ], and other epoxy cross-linking agents. These modified adhesives have been successfully used to fabricate high water-resistant plywood and blockboard in the wood panel industry [ 19 , 20 ].…”

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

“…Other chemical additives are also known to modify the properties of protein‐based adhesives. For example, sodium dodecyl sulfate (SDS) acts as a surfactant to denature protein chains, 19 thereby exposing more reactive functional groups. In a recent study, Liu et al 20 demonstrated that the acidic hydrogen of imidazole, which was added as a curing agent, was shown to form hydrogen bonds with the carbonyl group of the amide bonds of the adhesive.…”

Comparative Study of Plywood Boards Produced with Castor Oil-Based Polyurethane and Phenol-Formaldehyde Using Pinus taeda L. Veneers Treated with Chromated Copper Arsenate

“…Phenolic resins are acknowledged as the oldest synthetic thermosetting polymers [12]. The formaldehyde-based adhesives normally demonstrate high bond strength and still dominate the wood-based panel industry, especially given their low costs [13,14]. However, due the concerns about the potential indoor pollution, the development of environmentally friendly adhesives that are nontoxic and renewable is meaningful [12,13].…”

“…The formaldehyde-based adhesives normally demonstrate high bond strength and still dominate the wood-based panel industry, especially given their low costs [13,14]. However, due the concerns about the potential indoor pollution, the development of environmentally friendly adhesives that are nontoxic and renewable is meaningful [12,13]. Along with chemical versatility, high reactivity and excellent adhesive performance, the formaldehyde-based resins are related to some problems, such as free formaldehyde in the adhesives and the formaldehyde emission from the wood composites, as the volatile organic compounds are carcinogenic to humans and harmful to the environment [15].…”

“…Cai et al [21] prepared a high-performance resin from soy protein isolate and hybrid biomaterial to replace harmful formaldehyde adhesives for plywood production. Zhang et al [13] tested a tough, water-resistant, high bond strength resin derived from soybean meal and flexible hyper-branched aminated starch for plywood. Peng et al [22] designed a new method by using tannin for partial substitution of urea formaldehyde resin and inserted plasma pretreatment of wood to strengthen the bonding performance of plywood.…”