Preparation of a high-strength, hydrophobic performance starch-based adhesive with oxidative cross-linking via Fenton's reagent

"Isocyanates and isocyanides - life-threatening toxins or essential compounds?"

Isocyanides and isocyanates are some of the most reactive compounds in organic chemistry, making them perceived as compounds with high potential for use in both the laboratory and industry. With their high reactivity also comes several disadvantages, most notably their potentially high toxicity. The following article is a collection of information on the toxic effects of the isocyanide group on the human body and the environment. Information on the mechanism of how these harmful substances affect living tissues and the environment, worldwide information on how to protect against these chemicals, current regulations, and exposure limits for specific countries is compiled. The latest research on the application uses of isocyanates and isocyanides is also outlined, as well as the latest safer and greener methods and techniques to work with these compounds. Additionally, the presented article can serve as a brief guide to the organic toxicity of a group of isocyanates and isocyanates.

Development of environmentally friendly glyoxal-based adhesives with outstanding water repellency utilizing wheat gluten protein

To reduce the release of volatile organic compounds (VOCs) from formaldehyde-based adhesives at the source, the use of low-toxicity and biodegradable glyoxal instead of formaldehyde for the preparation of novel urea-glyoxal resins is a simple and promising strategy. The limited water resistance and adhesive strength of the new urea-glyoxal resins (UG) restrict their extensive application. This study prepared a high-performance, water-resistant WP-UG wood adhesive by combining UG prepolymer with wheat gluten protein (WP). FTIR, XRD, and XPS confirmed the existence of a chemical reaction between the two components, and thermal analysis showed that WP-UG plywood had better thermal stability. Evaluation of the gluing properties revealed that the dry and wet strengths of WP-UG adhesive bonded plywood reached 1.39 and 0.87 MPa, respectively, which were significantly higher than those of UG resin by 35 % and 314 %. The bond strength increased from 0 to 0.89 MPa after immersion in water at 63 °C for 3 h. The results indicated that the introduction of WP promoted the formation of a more complex and tightly packed crosslinking network and developed a glyoxal-based adhesive with high bond strength and water resistance. This study provides a new green pathway for novel urea-formaldehyde binders to replace harmful formaldehyde-based binders, which helps to increase their potential application value in the wood industry.

Valorization of a by-product of the yerba mate industry by assembling with cassava starch adhesive for packaging material production

Yerba mate industrial processing produces tons of powder as a by-product, this yerba mate powder (YMP) is an excellent source of biomass to develop biodegradable materials. Cassava starch modified with 1,2,3,4-butane tetracarboxylic acid (BA) in the presence of sodium propionate as a catalyst is an eco-friendly option to obtain bioadhesives. This work aimed to develop sustainable laminates from starch-based adhesives and yerba mate powder and to study their physico-chemical, structural, and mechanical properties. Blends of bioadhesive and YMP were prepared (1:1, adhesive:YMP). Monolayer materials were obtained by thermo-compression and later assembled with adhesive to obtain bilayer laminates. Bioadhesive was able to bind the yerba mate by-product fibers, as evidenced by SEM microstructure analysis, the interactions of adhesive:substrate were elucidated by ATR-FTIR and supported by chemometrics analysis. The incorporation of the catalyst decreased the rugosity of materials and their mechanical performance was improved by the action of both acid concentration and catalyst presence, requiring higher energy for puncture. Thus, it was feasible to obtain mono and bilayer laminates as an eco-compatible alternative for the design of sustainable tray-like materials based on the industrial by-product of yerba mate.

Preparation of reed fibers reinforced graft-modified starch-based adhesives based on quantum mechanical simulation and molecular dynamics simulation

Starch is a biomass polymer material with a high yield and comprehensive source. It is used as a raw material for preparing adhesives because of its highly active hydroxyl group. However, poor adhesion and water resistance hinder the application of starch-based adhesives (SBAs). Based on this, the starch was modified through graft copolymerization with itaconic acid as a cross-linking agent, methyl methacrylate and methyl acrylate as copolymers. Additionally, reed fibers were synergistically modified with polydopamine deposition to prepare an environmentally friendly SBA used in plywood production. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H NMR), X-ray diffraction (XRD), and thermogravimetric analysis (TG) demonstrate that copolymerization of methyl methacrylate and methyl acrylate with starch improves the shear strength, water resistance, and thermal stability of the SBA. Compared to unmodified starch, the modified SBA exhibits a 129 % increase in dry strength and achieves a wet strength of 1.36 MPa. Fukui function, Frontier orbit theory, and molecular dynamics simulation have shown that itaconic acid promotes the copolymerization of starch and acrylate monomers. The modified starch has fewer hydrogen bonds, less order, and a denser macromolecular network structure, which provides a reference for studying the molecular interaction mechanisms of SBAs.

Modification of biological starch macromolecule with phosphate and dimethylammonium chloride acyloxylate substituents confers good desizability, film properties, paste stability and adhesion

This study revealed the influence of phosphorylation-dimethylammonium chloride acyloxylation (PDACA) on the desizability, film properties, paste stability, and adhesion of biological starch macromolecules. A new starch-based sizing agent, phosphorylated-dimethylammonium chloride acyloxylated starch (PDACAS), was synthesized with degrees of substitution (DS) ranging from 0.033 to 0.065. Compared to control phosphorylated-quaternized starch (PQS, 87.4 %), the desizing efficiency of cotton yarns sized with PDACAS was ~94 %, exceeding the industrial minimum requirement of 90 %. The PDACAS film tensile properties were as follows: elongation at break of 3.31 %-3.78 %, bending endurance of 1131-1537 cycles, and tensile strength of 35.83-28.31 MPa, compared with those of acid-thinned starch (ATS) film (2.74 %, 957 cycles, and 38.12 MPa). The PDACAS had paste stability of ~92 %, compared with 83.3 % for ATS. The bonding forces (an indicator of adhesion to fibers) ranged from 107.1 N to 125.3 N for cotton roving, and 128.3 N to 148.7 N for polyester/cotton roving, which were significantly better than those of ATS (95 N for cotton and 117.9 N for polyester/cotton roving). Overall, PDACA treatment effectively avoided the adverse effect of high DS quaternization on the desizability of PQS and imparted good film properties, paste stability, and adhesion to starch.