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Lignin polymers

Fibers for commercial and domestic use are broadly classified as natural or synthetic. The natural fibers are vegetable, animal, or mineral ia origin. Vegetable fibers, as the name implies, are derived from plants. The principal chemical component ia plants is cellulose, and therefore they are also referred to as ceUulosic fibers. The fibers are usually bound by a natural phenoHc polymer, lignin, which also is frequentiy present ia the cell wall of the fiber thus vegetable fibers are also often referred to as lignocellulosic fibers, except for cotton which does not contain lignin. [Pg.357]

Sasaki, S. Nishida, T. Tsutsumi, Y. Kondo, R. Lignin dehydrogenative polymerization mechanism a poplar cell wall peroxidase directly oxidizes polymer lignin and produces in vitro dehydrogenative polymer rich in P-O-4 linkage. FEBS Lett. 2004, 562, 197-201. [Pg.419]

Proanthocyanidins and Procyanidins - In a classical study Bate-Smith ( ) used the patterns of distribution of the three principal classes of phenolic metabolites, which are found in the leaves of plants, as a basis for classification. The biosynthesis of these phenols - (i) proanthocyanidins (ii) glycosylated flavonols and (iii) hydroxycinnamoyl esters - is believed to be associated with the development in plants of the capacity to synthesise the structural polymer lignin by the diversion from protein synthesis of the amino-acids L-phenylalanine and L-tyro-sine. Vascular plants thus employ one or more of the p-hydroxy-cinnarayl alcohols (2,3, and 4), which are derived by enzymic reduction (NADH) of the coenzyme A esters of the corresponding hydroxycinnamic acids, as precursors to lignin. The same coenzyme A esters also form the points of biosynthetic departure for the three groups of phenolic metabolites (i, ii, iii), Figure 1. [Pg.124]

Phenylalanine, tyrosine, and tryptophan are converted to a variety of important compounds in plants. The rigid polymer lignin, derived from phenylalanine and tyrosine, is second only to cellulose in abundance in plant tissues. The structure of the lignin polymer is complex and not well understood. Tryptophan is also the precursor of the plant growth hormone indole-3-acetate, or auxin (Fig. 22-28a), which has been implicated in the regulation of a wide range of biological processes in plants. [Pg.859]

Pigment and filters Poly substituted phenol ethoxylates Phosphate esters Short chain amine EO/PO co-polymers Lignin sulphonates Wetters and dispersants... [Pg.12]

Lignocellulose denotes the mixture of the carbohydrate biopolymers cellulose and hemicellulose with the aromatic polymer lignin that is found in plants. Wooden raw materials consist mainly of cellulose (30-50 wt%), hemicellulose (10-40 wt%), and lignin (15-30 wt%). As the structure of cellulose (C6 carbohydrates) and hemicellulose (C5 carbohydrates) is quite similar, they will be discussed together in Section 2.2.2.1.1, followed by lignin, which has a very different composition (Section 2.2.2.1.2). [Pg.89]

As an amorphous polymer, lignin undergoes chain segment motion upon heating. This motion, a glass transition, is characteristic of all amorphous polymers, and is indicated by an endothermic shift in the DTA or DSC curves. This glass transition is accompanied by abrupt changes in free volume, heat capacity, and thermal expansion coefficient. [Pg.210]

Selective cleavage of ether bonds is useful to determine the contribution of carbon-carbon bonds for polymer lignin. Pivaloyl iodide [90] is known to cleave a-ether bonds selectively and trimethylsilyl iodide [91,92] can cleave a- and P-ether bonds quite effectively under the proper reaction conditions. Because of the very small amount of sample required, pyrolysis GC-MS may be applied for the analysis of a specific morphologi region of a cell wall. [Pg.31]

The biogenesis of lignans is strictly related to the production of the plant polymer lignin. Lignin is a constituent of the plant cell wall and together with hemicellulose cements the cellulose microfibrils thus connecting... [Pg.546]

Fig 3.7. Substrates used by fungi. The is an approximation to the relative number of species that can use the different types of carbon sources. Most fungal species can use monosaccharides. Few fungi can use the single carbon compounds like methane and few fungi can break down the very large and recalcitrant polymer lignin. [Pg.34]


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See also in sourсe #XX -- [ Pg.378 ]

See also in sourсe #XX -- [ Pg.24 ]




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Blends Lignin-containing polymers

Carbohydrates, compounds with lignin polymers

Coal lignin-like polymers

High-performance polymers from lignin

High-performance polymers from lignin degradation products

Lignin like polymers in coals

Lignin polymer, structure

Lignin polymers, phenolic building blocks

Lignin-containing polymers

Lignin-containing polymers polymer blends

Lignin-containing polymers preparation

Lignin-containing polymers properties

Lignin-containing polymers synthesis

New Polymers Derived from Chemicals Obtainable by Lignin Decomposition

Polymer lignin modifiers

Polymers formed from lignins

Specialty polymers from lignin

Thermoplastic polymers lignin-based thermoplastics

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