A High-Performance and Low-Cost Soy Flour Adhesive with a Hydroxymethyl Melamine Prepolymer

et al. 2020

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Bio-based adhesives have low water resistance and they are less durable than synthetic adhesives, which limits their exterior applications. In this study, a bio adhesive was developed from soybean meal and larch tannin that was designed for exterior use. Phenol hydroxymethylated tannin oligomer (PHTO) was synthesized and then mixed with soybean meal flour in order to obtain a soybean meal-based adhesive (SPA). The results showed that the moisture absorption rate, residual rate, and solid content of SPA with 10 wt % PHTO (mass ratio with respect to the entire adhesive) were improved by 22.8%, 11.6%, and 6.8%, respectively, as compared with that of pure SPA. The wet shear strength of plywood with SPA with 10 wt % PHTO (boiling in 100 °C water for 3 h) was 1.04 MPa when compared with 0 MPa of pure SPA. This met the bond strength requirement of exterior-use plywood (GB/T 9846.3-2004). This improved adhesive performance was mainly due to the formation of a crosslinked structure between the PHTO and the protein and also PHTO self-crosslinking. The formaldehyde emission of the resulting plywood was the same as that of solid wood. The PHTO-modified SPA can potentially extend the applications of SPAs from interior to exterior plywood.

Section: Thermal Stability and Ftir Analysissupporting

confidence: 84%

Soybean Meal-Based Wood Adhesive Enhanced by Phenol Hydroxymethylated Tannin Oligomer for Exterior Use

Chen

et al. 2020

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“…Between the depletion of global petrochemical resources and the increasingly serious environmental pollution problems they cause, development of renewable and environmentally friendly wood adhesives has become an important consideration for the wood industry going forward. Protein adhesives are made from raw materials that are available in abundance [3]. Moreover, they have the advantages of being non-toxic, renewable, and environmental- friendly [4,5]; and as such, have become a research hotspot in recent years.…”

Section: Introductionmentioning

confidence: 99%

Effects of Different Denaturants on Properties and Performance of Soy Protein-Based Adhesive

Meng

et al. 2019

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Chemical modification of soy protein, via crosslinking, is the preferred method for creating non-toxic, renewable, environmentally friendly wood adhesives. The denaturing process of protein is important for the adhesive performance improvement. In order to investigate the effect of different denaturing agents on the performance of soy protein-based adhesives before and after crosslinking modification. In this study, three different denaturing agents—urea (U), sodium dodecyl sulfate (SDS), and sodium hydrogen sulfite (SHS) and an epoxide crosslinking agent—Triglycidylamine (CA) were used to prepare soy protein-based adhesives. The results showed: (1) The denaturing agent unfolded protein molecules and exposed more hydrophobic groups to prevent water intrusion, which was mainly a contribution for the water resistance and performance improvement of soy protein-based adhesives. The wet shear strength was improved up to 91.3% (denaturing by urea). (2) After modifying by the crosslinking agent, the properties and performance improvement was due to the fact that the active groups on soybean protein molecules reacted with the crosslinking agent to form a crosslinking structure, and there is no obvious correlation with the hydrophobic groups of the protein. (3) The unfolded soybean protein molecules also expose hydrophilic groups, which facilitates the reaction between the crosslinking agent and protein to form a denser crosslinking structure to improve the performance of the adhesive. Particularly, after denaturing with SHS, the wet shear strength of the plywood bonded by the SPI-SHS-CA adhesive increased by 217.24%.

“…By incorporating 2 g of TGIC into the SM adhesive, the moisture uptake decreased by 15.1%. These reductions were attributed to the crosslinked network formation in adhesive system, preventing water intrusion [34]. When the DAS was introduced into the SM/TGIC, the SM/TGIC/DAS-5 exhibited a negligible increase in moisture uptake compared with the SM/TGIC sample, which confirmed that the DAS did not react with the SM/TGIC adhesive.…”

Section: Resultsmentioning

confidence: 99%

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

Chen

et al. 2019

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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.