American Society for Testing and Materials

Changes in both formaldehyde legislations and voluntary requirements (e.g. Germany RAL) are currently the driving factors behind research on alternatives to amino-based adhesives; moreover, consumer interest in healthy and sustainable products is increasing in bio-based adhesives. Sources of formaldehyde emissions in wood-based panels as well as different emission test methods have been discussed, and the main focus of this review is on the research conducted on sustainable bio-based adhesive systems for wood panels. Lignin, tannin, protein, and starch have been evaluated as both raw materials and adhesive alternatives to existing amino-based thermosetting adhesives. Adhesion improving modifications of these bio-based raw materials as well as the available and experimental crosslinkers have also been taken into account.

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Development of sustainable bio-adhesives for engineered wood panels – A Review

Camelina uses, genetics, genomics, production, and management

Different kinds of biorenewable materials are rapidly emerging as potential alternatives to conventional petroleum-based synthetic materials. Among these materials, soy protein and its derivatives are of utmost interest and importance due to their advantages such as low cost, biodegradability, environmental friendliness, biocompatibility, renewability, and wide availability to name few. However, the poor physicochemical/mechanical properties as well as high moisture sensitivity of different soy based materials limit their successful applications in many fields. Different methodologies to produce new soy based materials with suitable functional groups are highly desired to increase their range of applications. So, in this Review, we have focused on the recent advances in the various graft copolymerization strategies involving soy and its applications. The synthesis, characterization, and methodology of graft-copolymer processing and resulting properties of the copolymers are fully covered. In this Review, ...

Synthesis and Applications of Biodegradable Soy Based Graft Copolymers: A Review

There has been a rapid growth in research and innovation of bio-based adhesives in the engineered wood product industry. This article reviews the recent research published over the last few decades on the synthesis of bio-adhesives derived from such renewable resources as lignin, starch, and plant proteins. The chemical structure of these biopolymers is described and discussed to highlight the active functional groups that are used in the synthesis of bio-adhesives. The potentials and drawbacks of each biomass are then discussed in detail; some methods have been suggested to modify their chemical structures and to improve their properties including water resistance and bonding strength for their ultimate application as wood adhesives. Moreover, this article includes discussion of techniques commonly used for evaluating the petroleum-based wood adhesives in terms of mechanical properties and penetration behavior, which are expected to be more widely applied to bio-based wood adhesives to better evaluate their prospect for wood composites application.

https://www.mdpi.com/2073-4360/9/2/70/pdf

Bio-Based Adhesives and Evaluation for Wood Composites Application.

Adhesion properties of soy protein adhesives enhanced by biomass lignin

Physicochemical properties of soy protein adhesives modified by 2-octen-1-ylsuccinic anhydride

Utilization of sorghum lignin to improve adhesion strength of soy protein adhesives on wood veneer

The objective of this research was to study the adhesion properties of sodium bisulfite (NaHSO3)-modified canola protein. Protein was extracted from canola meal through alkali solubilization and acid precipitation methods, then modified with different concentrations of NaHSO3 (0–15 g/L) during the isolation process. As NaHSO3 concentration increased, canola protein purities decreased. Amino acid profiles showed that the hydrophobic amino acids in canola protein constituted only 27% of total protein, indicating that canola protein is mostly hydrophilic. The reducing effects of NaHSO3 were exerted on canola protein through the breaking of disulfide bonds in both its cruciferin and napin components, as reflected by the protein electrophoresis profile, DSC data, and morphological images. The wet protein isolates were used as adhesives. The greatest wet shear strength of canola protein adhesive without modification was 3.97 MPa with 100% wood cohesive failure (WCF), observed at a curing temperature of 190 °C. NaHSO3 had slight weakening effects on the adhesion performance of canola protein. Canola protein modified with 3 g/L NaHSO3 exhibited wet shear strength similar to the control at 190 °C and higher strength at 150 and 170 °C. The NaHSO3 modification significantly improved handling and flowability of canola protein adhesives.

Physicochemical Properties and Adhesion Performance of Canola Protein Modified with Sodium Bisulfite

Distillers dried grains with solubles (DDGS) is the main co-product from grain-based ethanol production. The objective of this research was to compare the adhesive performance of three types of sorghum proteins: acetic acid-extracted sorghum protein from DDGS (PI), aqueous ethanol-extracted sorghum protein from DDGS (PII) and acetic acid-extracted sorghum protein from sorghum flour (PF). Physicochemical properties including amino acid composition, and rheological, thermal and morphological properties also were characterized. Results showed that PI had the best adhesion performance in terms of dry, wet and soak adhesion strength, followed by PF and PII. The wet strength of PI at a concentration of 12% protein assembled at 150 °C was 3.15 MPa, compared to 2.17 MPa and 2.59 MPa for PII and PF, respectively. DSC thermograms indicated that the PF protein isolates contained higher levels of carbohydrates than PI and PII; such non-protein contaminants in the PF isolate could be the reason for its lower adhesion strength than PI. In addition, PI might have more hydrophobic amino acids aligned at the protein-wood interface than PII, which could explain the better water resistance of PI. The optimum sorghum protein concentration and pressing temperature for maximum adhesion strength was 12% and 150 °C. PI had a significantly higher wet strength (3.15 MPa) than unmodified soy protein (1.63 MPa for soy protein). The high percentage of hydrophobic amino acids in PI (57%) was likely a key factor in the increased water resistance of PI compared with soy protein (36% hydrophobic amino acids). These results indicated that sorghum protein has huge potential as an alternative to petroleum-based adhesives.

Ningbo Li

Papers

Adhesion properties of soy protein adhesives enhanced by biomass lignin

Physicochemical properties of soy protein adhesives modified by 2-octen-1-ylsuccinic anhydride

Utilization of sorghum lignin to improve adhesion strength of soy protein adhesives on wood veneer

Physicochemical Properties and Adhesion Performance of Canola Protein Modified with Sodium Bisulfite

Adhesive Performance of Sorghum Protein Extracted from Sorghum DDGS and Flour