Applications of Tannin Resin Adhesives in the Wood Industry

Tannin is extracted from natural sustainable materials. It is widely used to prepare tannin resin adhesives owing to its naturally occurring phenolic structure. This chapter aims to introduce the resources and structures of tannin, existing reactions that are involved in the synthesis of tannin resin, and the applications of tannin resin adhesives in the wood industry. Additionally, the advancements in the research based on the use of tannin resins in manufacturing plywood, particleboard, wood preservation, decoration paper impregnation, structural glulam, impregnated fibers, and other wooden products are reviewed. Herein, the main limitations encountered during the application of tannin resin adhesives and the future key research points are identified. Finally, the potential applications of tannin resin adhesives in the wood industry have been discussed

Wood Adhesive Fillers Used during the Manufacture of Wood Panel Products

During the manufacture of wood panel products, fillers are commonly added to wood adhesives to lower costs and give body to liquid adhesives and also reduce undesired flow or overpenetration into wood. The fillers used in wood adhesives are often neutral or weakly alkaline compounds that typically require no chemical reaction with curing agent, or other components. Fillers are mixed with other components prior to the application of resin on the surface of wood, wood veneer, or wood flakes. Fillers can be either organic (e.g., rye, wheat, walnut shell, and wood flours), or inorganic (e.g., calcium carbonate, calcium sulfate, aluminum oxide, or bentonites). Overall, fillers are low-cost materials for improving the properties of wood or even give it new functions

PERFORMANCE OF MUF RESINS FOR PARTICLEBOARDS BEFORE AND AFTER SPRAY-DRYING

Melamine-urea-formaldehyde (MUF) resins can be spray dried to obtain resins in powder form and indefinite shelf-life. Application as particleboard adhesives of such resins after redissolving them in water does yield resins of excellent performance as particleboard adhesives if the natural advancement caused by the heat in the spray-drier chamber is taken into account. CP MAS 13C NMR analysis of the spray-dried resin in powder form and thermomechanical analysis has shown some difference in behaviour in relation to MUF resins of the same level of water tolerance which have not been spray-dried. These small but significant differences can be ascribed to differences in resin structure

Physico-Mechanical Properties Of Plywood Bonded By Nano Cupric Oxide (Cuo) Modified Pf Resins Against Subterranean Termites

Nano CuO and alkane surfactant modified phenol Formaldehyde (PF) resins were applied to manufacture plywood, and physical and mechanical properties, such as shear strength, tensile property, modulus of rupture (MOR), modulus of elasticity (MOE), as well as termite resistance were evaluated. The result showed that the combination of nano CuO and alkane surfactantplayed different effect on tensile strength, and especially on shear strength as evaluated at different test conditions. But it was confirmed to improve the water resistance of treated plywood specimens. The introduction of nano CuO and surfactant did not influence the flexural properties significantly by statistically. The result of termite tests indicated that the weight loss decreases gradually from 31,12% to less than 10,37%, and the mortality increases from 32,61% to higher than 86,35%. And the AWPA rating also rises from 4 (very severe attack) to 7 (moderate attack)

Wood Plastic Composites: Their Properties and Applications

Wood plastic composites (WPCs) is one of crucial and potential engineering wood products that has been extensively employed in the fields of landscape, transportation, municipal engineering and building construction. It has gradually been used to replace the conventional wood-based composites. This chapter aims to introduce the properties and development of WPCs and illustrate how defects in their mechanical properties, biological and aging resistance, and flame retardance affect their global development. Herein, the effects on the biological durability of WPCs against algae, mold, fungi, and termites made with various wood species with different chemical extractive compositions, the natural weathering performance of WPCs and the mechanisms of protection against ultraviolet light and moisture, the effectiveness and mechanism of reinforcement of WPCs by novel alloy modification of linear and aromatic polyamides are reviewed. Additionally, the flame retardance properties, common testing methods as well as the performances of novel flame retardants for WPCs, are comparatively described. Lastly, the limitations and prospects of WPCs in future construction applications are also discussed

A novel fiber-veneer laminated composite based on tannin resin

Natural non-woven fiber was impregnated with a tannin resin and laminated with wood veneer for preparation of laminated composites. The tannin resin used showed a good compatibility with the natural fiber, and easy to assemble with the wood veneers. The tannin resin penetration into the wood veneer was observed by light microscopy. The laminated composite shows very good mechanical properties and water resistance. Shear force-displacement testing demonstrates that the laminated composite had a ductile behaviour under wet testing conditions. The laminated composite was prepared using 100% natural bio-renewable raw materials and had good properties compared to conventional plywood bonded with synthetic resin

Research Progress on the Health Benefits of Scented Tea

Scented tea, also known as fragrant tea, mainly comprises green tea as the tea base and the dried and processed flowers of various plants. It is a unique reprocessed tea in China. There are many types of scented tea, including jasmine, lily, osmanthus, rose and honeysuckle. The scenting process greatly influences the quality of the scented tea. Humidifying continuous scenting processes, frying flower processes and innovative drying methods have been developed to resolve the issues of cumbersome, time-consuming and low utilisation rates of flowers in the process of making scented tea. The main chemical components of scented tea are polyphenols as well as exogenous plant glycosides, flavonoids, lactones, coumarins, quercetin, steroids, terpenoids and other compounds. Scented tea plays an active role in the prevention and treatment of various diseases and has as anti-oxidant, anti-cancer, hypoglycaemic, hypolipidemic, immunomodulatory and neuromodulatory effects. This chapter mainly reviews and summarises the types of scented teas and their related health functions

Two ditetrazole derivatives as effective inhibitors for the corrosion of steel in CH3COOH solution

The inhibition performance of two ditetrazole derivatives of blue tetrazolium (BT) and nitrotetrazolium blue chloride (NTBC) on cold rolled steel (CRS) in 2.5 M CH3COOH solution was studied by weight loss, electrochemical techniques and scanning electron microscope (SEM). Quantum chemical calculations of BT2+ and NTB2+ were performed to theoretically investigate the adsorption mechanism. The results show that both BT and NTBC behave as effective inhibitors, and their maximum inhibition efficiency values are higher than 92% at 0.20 mM. The inhibition follows the order of NTBC > BT. The adsorption of either BT or NTBC on steel surface follows Langmuir isotherm. BT and NTBC can be arranged as mixed-type inhibitors. The presence of BT or NTBC increases the charge transfer resistance, and decreases the corrosion degree of steel surface in CH3COOH. The adsorption centers are mainly focused on two tetrazole rings as well as the linkers of two benzene rings. Keywords: Corrosion inhibitor, Acetic acid, Steel, Blue tetrazolium, Nitrotetrazolium blue chloride, Adsorptio

Synthetic and natural materials for wood adhesive resins

Des résines vertes à base de lignine, tanins et protéines de soja ont été étudiées. La faisabilité et le mécanisme de l utilisation du glyoxal à différents taux en substitution du formaldéhyde ont été analysés. Une optimisation dans la préparation des panneaux de particules à été réalisée. Les résultats issus de ces travaux confirment les quelques aspects: Des colles à base de lignine et de soja glyoxalé mélangé à la pMDI et au tanin de mimosa satisfaisant les exigences données par les normes internationales pour la fabrication des panneaux de particules ont été obtenues. Aucun formaldéhyde n a été utilisé dans les formulations. La performance a été déterminée en majeure partie en fonction de la proportion de pMDI ajoutée. Les résultats obtenus prouvent l existence de réactions entre lignine et glyoxal, protéines de soja et glyoxal. Mais pour la formulation de protéines de soja, les groupes hydroxyles qui en résultent n ont pas pu réticuler. Des études ont été effectuées sur l influence de la nano-montimorillonite (MMT) sur des résines à base d urée et de phénol-formaldéhyde. Le taux d exfoliation de la MMT mélangée avec ces résines était déterminé. Des études thermiques et mécaniques de ces systèmes ont été réalisées. Les conclusions obtenues sont les suivantes : L étude que la Na-MMT est intégralement exfoliée quand elle est mélangée avec des résines UF, alors qu elle n a que quelques degrés d intercalation lorsqu elle est ajoutée à des résines PF ou PUF. L ajout d un faible pourcentage de Na-MMT ne semble pas modifier significativement la performance des résines sèches mais la résistance à l eau des panneaux contenant des résines UF ou phénolique s est vue augmenter.Environment-friendly tannin/lignin and soy protein-based wood adhesive were studied. The feasibility and mechanism to use glyoxal to substitute formaldehyde in relevant formulations was analyzed. The suitable addition percentage was determined. The lab-prepared particleboard procedure was optimized too. The results shown in this work confirmed few aspects: Lignin-based adhesives and glyoxalated soy-based wood adhesives mixed with pMDI and mimosa tannin satisfying the requirements of relevant international standards for the manufacture of wood particleboard were obtained. These lignin-based or soy-based wood adhesives did not use any formaldehyde in their formulation. The performance of these formulations is determined to a great degree by the amount or proportion of the pMDI used. The results proved that the reaction between lignin and glyoxal, soy protein and glyoxal. But for the latter, the hydroxy groups that resulted couldn t condense to a cross-linked structure. Some work has been done on the study of the influence of nano-montmorillonite (MMT) on urea-formaldehyde resin and phenolic resin adhesives. The level of exfoliation of the MMT being mixed with these resins was determined. Some conclusions can be drawn: Na-MMT is completely exfoliated when mixed with UF resins, while it only has some degree of intercalation when added to PF and PUF resins. The addition of small percentages of Na-MMT does not appear to improve much the resins dry performance, while it seems to increase the water resistance of the UF-bonded and phenolic-bond panels.NANCY1-Bib. numérique (543959902) / SudocSudocFranceF

Influence of Gender on the Mechanical and Physical Properties of Hemp Shiv Fiber Cell Wall in Dioecious Hemp Plant

Hemp (Cannabis sativa L.) shiv has great potential for the production of bio-composites as a reinforcement material. To gain more information about hemp shiv, this research studied the influence of gender on the physical and mechanical properties of the fiber cell wall in the shiv of three dioecious hemp plant varieties by optical microscopy, image analysis software, WXRD, and nanoindentation. The results show that a hemp plant’s gender greatly influences the properties of hemp shiv. While long and thin in female hemp shiv, the fibers are shorter with a larger diameter in male hemp shiv. In addition, the cell walls in female shiv are thinner than those in male shiv. The microfibril angle (MFA), relative degree of crystallinity, elastic modulus, and hardness values of fiber cell walls as well as the lignin content in male hemp plants are higher than those in female hemp plants. Besides, the relationship between mechanical properties and MFA do not align with those observed in previous research, which shows that the gender of an individual plant has a greater effect on the mechanical properties of the fiber cell wall than does its MFA. Thus, when the fiber from this dioecious plant is investigated or used, the sex of the plant should be known and considered