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Natural Phenolic Adhesives derived from Tannins and Lignin
Published in A. Pizzi, K. L. Mittal, Handbook of Adhesive Technology, 2017
Condensed tannins, on the other hand, constituting more than 90% of the total world production of commercial tannins (200,000 tn./year), are both chemically and economically more interesting for the preparation of adhesives and resins. Condensed tannins and their flavonoid precursors are known for their wide distribution in nature and particularly for their substantial concentration in the wood and bark of various trees. These include various Acacia (wattle or mimosa bark extract), Schinopsis (quebracho wood extract), Tsuga (hemlock bark extract), and Rhus (sumac extract) species, from which commercial tannin extracts are manufactured, and various Pinus bark extract species. Where bark and wood of trees were found to be particularly rich sources of condensed tannins, commercial development ensued through large-scale afforestation and/or industrial extraction, mainly for use in leather tanning. The production of tannins for leather manufacture reached its peak immediately after World War II and has since progressively declined. This decline of their traditional market, coupled with increased price and decreased availability of synthetic phenolic materials due to the advent of the energy crisis of the early 1970s, stimulated fundamental and applied research on the use of such tannins as a source of condensed phenolics.
Phenolic Compounds potential health Benefits and toxicity
Published in Quan V. Vuong, Utilisation of Bioactive Compounds from Agricultural and Food Waste, 2017
Deep Jyoti Bhuyan, Amrita Basu
Tannins are the third important group of polyphenolics which can further be divided into two subcategories: condensed and hydrolysable tannins (Porter 1989). These are high-molecular-weight polymers. Fruits, grains and legumes consist of condensed tannins which are mainly polymers of catechins or epicatechins, whereas hydrolysable tannins are polymers of gallic or ellagic acid and found in berries and nuts (King and Young 1999). Condensed tannins are also known as proanthocyanidins and polyflavonoid, consisting of chains of flavan-3-ol units. They usually accumulate in the outer layers of plants (Ho 1992, King and Young 1999).
Tannins for Wood Adhesives,Foams and Composites
Published in Zhongqi He, Bio-based Wood Adhesives, 2017
This chapter has focused on the condensed tannins industrial extraction methods and utilizations. It also includes the results and perspectives of the recent studies in these fields. Although condensed tannins have been industrially used for very long time, with the turn of the 21st century a revival is obseved with an extension of their industrial use to green materials like adhesives, resins for composite and foams. The future of the green materials discussed in this chapter should accelerate for economic and environmental reasons.
Preparation and properties of a novel type of tannin-based wood adhesive
Published in The Journal of Adhesion, 2022
Xinyi Chen, Antonio Pizzi, Emmanuel Fredon, Christine Gerardin, Jinxing Li, Xiaojian Zhou, Guanben Du
Now, for a number of years, some biomass resources, including lignin,[4–7] tannin,[8–10] protein,[11–13] non-food starch[,14,15] and agricultural or forest residues,[16–18] have attracted the attention of researchers to prepare some high-performance wood adhesives. Among these, condensed tannins have been considered to have some interesting features to prepare wood adhesive.[19] Initially, condensed tannins phenolic nature led to their use to prepare adhesives similar to phenol-formaldehyde (PF) wood adhesive.[8–10,19,20] It is encouraging that tannin-formaldehyde wood adhesives have been successful commercially for many years.[19] However, formaldehyde, was still an essential component, even though formaldehyde-emission has been improved by some extent.[21] Therefore, low or no aldehyde tannin adhesives have been developed by a number of approaches. Hexamethylenetetramine (hexamine),[22,23] glyoxal,[24] furfuryl alcohol,[25] polymeric diphenylmethane diisocyanate (p-MDI),[23,26] poly-ethylenimine (PEI),[27] as well as carbohydrates-generated non-toxic and non-volatile aldehydes by specific oxidation,[28] were used to react with different condensed tannins to produce tannin-based wood adhesive without any kinds of volatile and toxic aldehydes. Certainly, some tannin wood adhesives were obtained though biomass resources (starch) mixing with condensed tannin, and alternative aldehydes acting as cross-linkers, leading to low formaldehyde emission.[13,29–31] Apparently, these improved adhesive formulations reduced effectively the toxic raw-materials consumption and formaldehyde-emission, as well as increasing biomass content.
Soy-based, tannin-modified plywood adhesives
Published in The Journal of Adhesion, 2018
Saman Ghahri, Antonio Pizzi, Behbood Mohebby, Ahmad Mirshokraie, Hamid Reza Mansouri
Thus, natural vegetable tannins are an excellent choice to use as modifiers of soy-based resins. Traditionally, vegetable tannins are used to make hard-wearing leathers. There are two main groups of tannins, namely hydrolysable and condensed tannins. The greater part of tannins produced in the world are condensed tannins such as mimosa bark tannin extract. Condensed tannins, but also a hydrolysable tannin such as chestnut tannin extract, have already been successfully used as wood panel adhesives [14–20] showing good properties.
Biological activities and determination of the mode of action of Tunisian Globularia alypum and Cistus monspeliensis ethanolic extracts
Published in International Journal of Environmental Health Research, 2022
Khaoula Nefzi, Karama Charfi, Abderrazek Maaroufi, Karim Hosni, Kamel Msaada, Mokhtar Baraket, Zouhaeir Nasr
To quantify tannin in species extracts, the vanillin method described by Broadhurst and Jones (1978) was used. The absorbance was measured at a wavelength of 500 nm against a blank containing pure acetone (Sun et al. 1998) (Cecil Aurius Series CE 2021). Condensed tannin contents are determined with reference to a standard curve (0 to 500 µg/ml catechin). As for flavonoids, condensed tannin contents are expressed in mg of catechin equivalent per gram of DM.