Mechanical and water-resistant properties of rice straw fiberboard bonded with chemically-modified soy protein adhesive

Edible, strong, and low-hygroscopic bacterial cellulose derived from biosynthesis and physical modification for food packaging

BACKGROUND

The pervasive presence of plastic packaging has led to significant environmental contamination due to excessive reliance on petrochemicals and the inherent non-biodegradability of these materials. Bacterial cellulose (BC) films present a viable alternative for food packaging applications, owing to their environmentally friendly synthesis process, non-toxic nature, robust mechanical strength, and biodegradability. However, the high hygroscopicity of such bio-based materials has limited their widespread adoption, as it results in diminished strength and barrier properties. In this study, a novel approach for creating edible, transparent, robust, and high-barrier BC-based composite packaging was proposed through biosynthesis with the incorporation of soy protein isolate and the physical interpenetration of calcium alginate-polyethylene glycol as a composite coating.

RESULTS

The finding demonstrated that the synthesized bio-based composite material exhibits stability in water, high optical transparency, complete oil resistance, and full degradability within 1 to 2 months. Furthermore, the composite material displayed enhanced mechanical properties in both dry and wet conditions, with a tensile strength of approximately 84 MPa, outperforming commercially available kraft paper and low-density polyethylene.

CONCLUSIONS

Soy protein isolate established a rigid, coherent, and homogeneous network with BC fibrils, thereby augmenting mechanical properties. Calcium alginate can be effectively combined with BC, utilizing polyethylene glycol as a binder and plasticizer, to generate a densely packed structure with reduced hygroscopicity. This bio-based composite material demonstrated considerable potential for application in food packaging and other value-added sectors as a substitute for non-degradable plastics. © 2023 Society of Chemical Industry.

Modeling the Bending Strength of MDF Faced, Polyurethane Foam-Cored Sandwich Panels Using Response Surface Methodology (RSM) and Artificial Neural Network (ANN)

The present study evaluates and compares predictions on the performance and the approaches of the response surface methodology (RSM) and the artificial neural network (ANN) so to model the bending strength of the polyurethane foam-cored sandwich panel. The effect of the independent variables (formaldehyde to urea molar ratio (MR), sandwich panel thickness (PT) and the oxidized protein to melamine-urea-formaldehyde synthesized resin weight ratio (WR)) was examined based on the bending strength by the central composite design of the RSM and the multilayer perceptron of the ANN. The models were statistically compared based on the training and validation data sets via the determination coefficient (R2), the root mean squares error (RMSE), the absolute average deviation (AAD) and the mean absolute percentage error (MAPE). The R2 calculated for the ANN and the RSM models was 0.9969 and 0.9960, respectively. The models offered good predictions; however, the ANN model was more precise than the RSM model, thus proving that the ANN and the RSM models are valuable instruments to model and optimize the bending properties of the sandwich panel.

Improved performance of soy protein adhesive with melamine-urea-formaldehyde prepolymer

In recent years, soy protein adhesive, as an environmentally friendly bio-based adhesive, has attracted extensive attention. In this study, in order to ameliorate the bonding quality of soy protein isolate (SPI) adhesive, the melamine–urea–formaldehyde prepolymer (MUFP) was synthesized, and different amounts of it were introduced into the SPI adhesive as a cross-linking agent. Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analyze (TGA), and scanning electron microscopy (SEM) were used to analysis the mechanism of modification. The results of plywood test indicated that the wet bonding strength of the adhesives was first increased and then decreased with an increase in the amount of MUFP additive. FT-IR, TGA, and SEM tests suggested that the introduction of MUFP could promote the establishment of a cross-linking structure in the cured adhesive layer to improve the bonding quality of adhesives, but presence of excessive MUFP could introduce hydrophilic groups and adversely affect water resistance.

In recent years, soy protein adhesive, as an environmentally friendly bio-based adhesive, has attracted extensive attention.

Biomimetic water-in-oil water/pMDI emulsion as an excellent ecofriendly adhesive for bonding wood-based composites

In this study, a novel and environmental strategy inspired by mussels is reported for the construction of a high-performance water-in-oil water/pMDI adhesive with strongly adherent catechol groups. It is found that the design of the biomimetic water-in-oil emulsion significantly increases the apparent viscosity and storage stability of the adhesive, which in turn influences the handling and bonding performance in practical application. Additionally, although the biomimetic emulsion design consumes part of active isocyanate groups in the pMDI, the contained catechol can serve as a reactive platform to induce secondary crosslinking interactions with the wood substrate to further improve the mechanical and adhesion performances of the modified pMDI adhesives. Consequently, compared to the pristine pMDI sample, the wet shear strength of the biomimetic water-in-oil water/pMDI adhesive is increased by 129.7 %, exhibiting that the obvious optimization of adhesion and water resistance properties. Overall, our findings provide new insights into exploiting novel and superior wood adhesives, and the constructed high-performance adhesive presents potential applications for sustainable wood products.

A Tough and Mildew-Proof Soybean-Based Adhesive Inspired by Mussel and Algae

Despite the recent advances in protein-based adhesives, achieving strong adhesion and mold resistance in wet environment is challenging. Herein, a facile fabrication technology of preparing tough bio-adhesive by incorporating soybean meal and blood meal is presented. Inspired by the marine mussel byssi and brown algae, metal coordination was introduced into a loosely bound protein system to construct multiple chemical cross-linking networks. Mixed alkali-modified blood meal (mBM) was mixed with soybean meal, then 1,6-hexane dioldiglycidyl ether (HDE) and zinc ion were introduced to fabricate soybean meal and blood meal-based adhesives. The attained adhesives exhibited good thermal stability, water resistance (the wet shear strength is 1.1 MPa), and mold resistance, with appropriate solid content (34.3%) and relatively low moisture uptake (11.9%). These outstanding performances would be attributed to the reaction of 1,6-hexane dioldiglycidyl ether with protein to form a preliminary cross-linking network; subsequently, the coordination of zinc ions with amino or carboxyl strengthened and toughened the adhesive. Finally, the calcium ions gelled the adhesives, providing cohesion force and making the network structure more compact. This study realized the value-added utilization of protein co-products and developed a new eco-friendly bio-based adhesive.

Sodium dodecyl sulfate improves the properties of bio-based wood adhesive derived from micronized starch: Microstructure and rheological behaviors

Enhancing the performance of starch-based wood adhesive is vitally important for its practical applications. Accordingly, we designed the use of micronized starch (MS) to prepare micronized starch-based wood adhesive (MSWA) by incorporating 0, 2, 4 and 6% (w/w, dry basis starch) sodium dodecyl sulfate (SDS). The results showed that 2% SDS exhibited remarkable improvement in shear strength and viscosity of MSWA. The grafted reaction was demonstrated by ¹H NMR and the steady shear results indicated that the adhesive possessed a pseudoplastic behavior under yield stress conditions. Besides, dynamic rheological measurements were applied to evaluate the structure of MSWA under varying frequencies, temperatures and constant stain. The transmission electron microscopy (TEM), Zeta potential and surface tension indicated that SDS could improve the surficial properties. Meanwhile, the microstructure of adhesive films and fracture surfaces of glued wood veneers by scanning electron microscopy (SEM) demonstrated that the migration of SDS led to the formation of surfactant layer. Furthermore, element analysis revealed the distribution of S/N in latex slices. The results of this study provide the detailed information about the influence of SDS on the rheological properties and microstructures of MSWA, which may facilitate the preparation of high performance bio-based adhesive for wood applications.