Preparation and characterization on the eco-friendly corn starch based adhesive of with salient water resistance, mildew resistance

Starch adhesive is a commonly used bonding glue that is sustainable, formaldehyde-free and biodegradable. However, there are obviously some problems related to its high viscosity, poor water and mildew resistance. Hence, exploring a starch-based adhesive with good properties that satisfies the requirements of wood processing presents the context of the current research. Thus, corn starch was used as raw material to form oxidized starch (OCS) via oxidation using sodium periodate, it was reacted with a synthesis polyurea compound that prepared from hexanediamine-urea (HU) obtained by deamination to yield a oxidized starch-hexanediamine-urea adhesive (denoted hereafter as OCSHU). The oxidation process was optimized in terms of oxidant concentration, reaction time and temperature. Furthermore, the impact of HU addition on the mechanical properties of the adhesive was explored. Results indicate adhesive exhibited outstanding shear strength, when 13 % of NaIO4 was used as an oxidant to treat starch at 55 °C for 24 h, and involved in a subsequent reaction with 40 % of HU. The dry shear strength, 24 h cold water strength, 3 h hot water strength and 3 h boiling water strength are 1.84, 1.50, 1.32, and 1.31 MPa. Meantime, OCSHU adhesive solution revealed good storage stability whereas cured resin exhibited mildew resistance. The developed adhesive is a simple and green biomass wood adhesive.

Synthesis and characterization of a bio-aldehyde-based lignin adhesive with desirable water resistance

Wood-based panels find widespread application in the furniture and construction industries. However, over 90 % of adhesives used are synthesized with formaldehyde, leading to formaldehyde emission and associated health risks. In this study, an entirely bio-based adhesive (OSL) was innovatively proposed through the condensation of multi-aldehyde derived from the oxidization of sucrose (OS) with sodium lignosulfonate (L). This approach positioned oxidized sucrose (OS) as a viable substitute for formaldehyde, ensuring safety, simplicity, and enhance water resistance upon reaction with L. The optimization of the OSL adhesive preparation process involved determining the oxidant level for high sucrose conversion to aldehyde (13 % based on sucrose), the mass ratio of OS to L (0.8), and hot-pressing temperature (200 °C). Notably, the shear strength of 3-plywood bonded with the developed adhesive (1.04 MPa) increased to 1.42 MPa after being immersed in hot water at 63 ± 3 °C for 3 h. Additionally, the plywood specimens exhibited excellent performance after soaking in boiling water for 3 h, resulting in a shear strength of 1.03 MPa. Chemical analysis using Fourier-transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) confirmed an addition reaction between L and OS, forming a dense network structure, effectively enhanceing the water resistance of OSL adhesives. Furthermore, compared with lignin-formaldehyde resin adhesive (LF), the OSL adhesive exhibited superior wet shear strength. This study offered an innovative approach for developing lignin-based adhesives utilizing a biomass aldehyde (OS), as a promising substitute for formaldehyde in the wood industry. The findings indicated that this approach may advance lignin-based adhesives, ensuring resistance to strength deterioration under highly humid environmental conditions.

Developing high performance biodegradable film based on crosslinking of cellulose acetate and tannin using caprolactone

The use of metal catalysts during the production process of cellulose acetate (CA) film can have an impact on the environment, due to their toxicity. Diphenyl phosphate (DPP) was used instead of toxic metal catalyst to react with cellulose acetate, tannin (T) and caprolactone (CL) for preparation of cellulose acetate-caprolactone-tannin (CA-CL-T) film. The results show that DPP can produce a cross-linked network structure composed of tannin, caprolactone and cellulose acetate. The maximum molecular weight reached 113,260 Da. The introduction of tannin and caprolactone into cellulose acetate caused the resulting CA-CL-T film acquire excellent strengthening/toughening effect, in which a tensile strength of 23 MPa and elongation at break of 18 % were attained. More importantly, the resistance of the film to UV radiation was significantly improved with the tannin addition, which was corroborated by the CA-CL-T film still exhibiting a tensile strength of 13 MPa and elongation at break around 13 % after continuous exposure to UV radiation for 9 days. On the other hand, the insertion of caprolactone provoked enhancement of the overall moisture resistance. Five days treatment of the films with Penicillium sp. induced gradual drop in quality, indicating the CA-CL-T film show response to biodegradation. In all, the effective crosslinking between the components of the developed material is responsible for the acquired set of these distinct characteristics.

Development and Characterization of Bio-Based Formaldehyde Free Sucrose-Based Adhesive for Fabrication of Plywood

In order to solve the problem of excessive consumption of petrochemical resources and the harm of free formaldehyde release to human health, biomass raw materials, such as sucrose (S) and ammonium dihydrogen phosphate (ADP) can be chemically condensed in a simple route under acidic conditions to produce a formaldehyde free wood adhesive (S-ADP), characterized by good storage stability and water resistance, and higher wet shear strength with respect to petroleum based phenolic resin adhesive. The dry and boiling shear strength of the plywood based on S-ADP adhesive are as high as 1.05 MPa and 1.19 MPa, respectively. Moreover, is Modulus of Elasticity (MOE) is as high as 4910 MPa. Interestingly, the plywood based on the developed S-ADP adhesive exhibited good flame retardancy. After burning for 90 s, its shape remains unchanged. Meanwhile, it can be concluded from thermomechanical analysis (TMA) and thermogravimetric analysis (TGA) that the S-ADP acquired excellent modulus of elasticity (MOE) and good thermal stability. It is thus thought promisingly that the use of S-ADP adhesive as a substitute for PF resin adhesive seems feasible in the near future.

An Investigation into the Relationship between Density and Pulverization Ratio for Tannin-Furanic Foam

Four types of classical tannin-based foam samples were prepared via different methods in the current study with an attempt to find out the impact of each one on the physico-mechanical properties. The results of performed tests showed similarity to the general trend of related research, with typical negative relation between the foam density and mechanical strength. A critical point was found for each type of foam samples, for example, for tannin-formaldehyde foams (TFF), they were in the range of 85-95 kg/m3, while for tannin-glutaraldehyde foams (TGF), mechanically-generated tannin foams (MTF) and steam-driven tannin furanic foams (STDF), they were about 52-62 kg/m3, 53-63 kg/m3, and 73-83 kg/m3, respectively. This implies a significant change for density and mechanical strength, has been dig out by intensive experimental results and analysis. In addition, a non-liner relationship between density and pulverization ratio was obtained by fitting the curves obtained by the experiment results. Finally, visualization using scanning electron microscopy (SEM) together with evaluation of the compression strength presented a deeper insight to illustrate the different factors affecting foam density and pulverization ratio.

Preparation and Characterization of Biomass Tannin-Based Flexible Foam Insoles for Athletes

The exploitation of bio-based foams implies an increase in the use of renewable biological resources to reduce the rapid consumption of petroleum-derived resources. Both tannins and furfuryl alcohol are derived from forestry resources and are, therefore, considered attractive precursors for the preparation of tannin-furanic foams. In addition, toughening modification of tannin-furanic foams using polyvinyl alcohol (PVOH) results in a more flexible network-like structure, which imparts excellent flexibility to the foams, whose relative properties are even close to those of polyurethane foams, which are the most used for fabrication of insoles for athletes. In addition, the addition of PVOH does not affect the thermal insulation properties of the foams by testing the thermal conductivity, resilience, and elongation at break, while reducing the brittleness of the samples and improving the mechanical properties. Also, the observation of the morphology of the foam shows that the compatibility between PVOH and tannin-furanic resin is good, and the cured foam does not show fragmentation and collapse, while the bubble pore structure is uniform. The developed flexible foam derived from biomass resources endows the foam with good thermal insulation properties and high mechanical properties, and the samples exhibit suitable physical parameters to be used as flexible insoles for athletes.

Facile Fabrication of High-Performance Composite Films Comprising Polyvinyl Alcohol as Matrix and Phenolic Tree Extracts

Given that tree extracts such as tannin and lignin can be efficiently used as modifying materials, this helps to verify the global trend of energy saving and environment protection. Thus, bio-based biodegradable composite film incorporating tannin and lignin as additives, together with polyvinyl alcohol (PVOH) as a matrix (denoted TLP), was prepared. Its easy preparation process endows it with high industrial value in comparison to some bio-based films with complex preparation process such as cellulose-based films. Furthermore, imaging with scanning electron microscopy (SEM) shows that the surface of tannin- and lignin-modified polyvinyl alcohol film was smooth, free of pores or cracks. Moreover, the addition of lignin and tannin improved the tensile strength of the film, which reached 31.3 MPa as indicated by mechanical characterization. This was accounted for by using Fourier transform infrared (FTIR) and electrospray ionization mass (ESI-MS) spectroscopy, which showed that the physical blending of lignin and tannin with PVOH was accompanied by chemical interactions that gave rise to weakening of the prevailing hydrogen bonding in PVOH film. In consequence, the addition of tannin and lignin acquired the composite film good resistance against the light in the ultraviolet and visible range (UV-VL). Furthermore, the film exhibited biodegradability with a mass loss about 4.22% when contaminated with Penicillium sp. for 12 days.

Investigation of Potential Use of Soybean Protein Isolate–Chinese Bayberry Tannin Extract Cross-Linked Films in Packaging Applications

The possibility of using commercial bayberry tannin (BT) from a Chinese source as a cross-linker and functional additive to develop soybean protein isolate (SPI)-based films was explored in this study by using the solvent casting method. In particular, the impacts of BT loading on the tensile strength, microstructure, thermal stability, water resistance and antioxidant capacity were fully investigated. The results reveal that SPI incorporated with BT yielded a phenolic–protein hybrid whose relevant films exhibited an improvement in tensile strength of around two times greater compared with native SPI as a result of the formed interactions and covalent cross-links, which could be proven using FTIR spectroscopy. The introduction of BT also led to the compact microstructure of SPI–BT films and enhanced the thermal stability, while the water vapor permeability was reduced compared with the control SPI film, especially at high loading content of tannin. Additionally, the use of BT significantly promoted the antioxidant capacity of the SPI-based films according to DPPH radical scavenging assay results. On this basis, Chinese bayberry tannin is considered a promising natural cross-linker and multifunctional additive that can be dedicated to developing protein-derived films with antioxidant activity for food packaging applications.

Impact of graphene/graphene oxide on the mechanical properties of cellulose acetate membrane and promising natural seawater desalination

New formulations of cellulose acetate (CA) membrane with graphene (G)/graphene oxide (GO) are suggested and investigated in the present work. This study is intended to find a wide range of conditions for fabricating CA membranes in the presence of some additions of graphene (G), and graphene oxide (GO). The membrane is prepared by phase inversion process. Microscopic investigations for graphene (G), graphene oxide (GO), and prepared membrane were performed by high-resolution transmission electron microscope (HRTEM) and scanning electron microscopy (SEM). The mechanical properties of prepared membranes are determined and evaluated. Permeation tests were performed using natural seawater and simulated seawater to check the prepared membrane performance. The results presented that the permeate flux of M25% CA membranes containing 0.01 wt.% G is the highest flux (57–74 l/m2 h) compared with the neat CA membrane, and the 0.01 wt.% GO-based membranes, while the GO-based membranes were comparable as the neat CA membrane at operating pressures (30–35 bar) and with a feed of 35 g/l NaCl solution. The results showed a remarkable salt rejection of simulated seawater of 95%, and natural seawater with a feed from the Mediterranean Sea displayed 90% salt rejection and accepted pure water flux as well.

Fabrication of single-walled carbon nanotubes from vulcanized scrap rubber via thermal chemical vapor deposition

Scrap rubber is a cheap alternate to valuable hydrocarbons in order to fabricate carbon nanotubes via thermal chemical vapor deposition.