wood cell wall 1-8-08 - Wood Cell Wall Douglas J. Gardner,...

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1 Wood Cell Wall Douglas J. Gardner, Professor Wood-Polymer Hybrid Composites The Woody Cell Chemical Structure Primary components A. Polysaccharides (Hollocellulose) - 60 - 85% 1) Cellulose - 40 - 50% 2) Hemicellulose - 20 - 35% B. Lignin 15 - 35% Secondary components A. Extractives 1) Tannins 2) Volatile oils and resins 3) Gums, latex, alkaloids, etc. B. Inorganics (ash) < 1%
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2 Isolation of cell wall components Wo d Extract fre wo d Total lignin Delignification Liquid Solid Hol ocel ulose Hemicel ulose Cel ulose remove extractives Degraded lignin Degraded carbs. Chemical Composition of Wood Component Hardwoods (%) Softwoods (%) Cellulose 40 50 40 45 Hemicellulose 25 35 25 30 Lignin 15 25 25 35 Extractives 0 10 0 10 Ash 1 1
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3 Cellulose • Comprised of Glucose monomers • Cellulose - most abundant organic chemical on earth • Cellulose - is the same in all plant materials Hemicellulose Hemicellulose - shows minor variations in structure A. Xylans: predominate in hardwoods. Anhydro forms of 1) xylose – 2) arabinose – 3) 4 - methyl glucuronic acid B. Galactoglucomannans: predominate in softwoods – 1) galactose – 2) glucose – 3) mannose
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4 Lignin Second most abundant chemical on earth Major "backbone" is the same (C-9 unit) Amorphous polymer in the cell wall although recent evidence has shown it to be ordered. Thermoplastic in nature Physically it imparts rigidity and stiffness to cell walls. Hardwoods 50 - 50 guaiacyl/syringyl Softwoods 90 -100% guaiacyl Extractives Represent an extremely wide range of classes of organic compounds. Color and odor of wood due to extractives. Extractives can be used to
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This note was uploaded on 12/21/2010 for the course AEWC 430 taught by Professor Dg during the Fall '08 term at University of Maine Orono .

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wood cell wall 1-8-08 - Wood Cell Wall Douglas J. Gardner,...

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