What is the composition of wood


Wood, a natural composite material consisting essentially of dead cell wall substance and consisting of the 3 main components cellulose, hemicellulose and lignin. In addition, the so-called wood constituents (accessory wood components) occur in the H., which can be assigned to different groups of substances (e.g. terpenes, lipoids, phenols, nitrogen compounds, mineral components wood ash) and in different compositions and quantities in the various tree species and tree parts occurrence.

The wood polysaccharides are essentially the carriers of the tensile strength, the lignin the carriers of the compressive strength in the polymer composite. The wood constituents influence the smell, taste, color, impregnability, resistance to fungi and insects etc., but only to a minor extent the strength properties of the wood.

The elemental composition of wood is approximately: 50.5% carbon, 6.4% hydrogen, 43% oxygen, 0.3% mineral components (wood ash), less than 0.1% nitrogen. Extract-free wood from conifers and hardwoods consists of around 40 to 44% cellulose. Conifers, on the other hand, contain more lignin (27-32%) and less hemicelluloses (20-25%) than hardwoods (18-24% lignin, 30-35% hemicelluloses).

The components are separated on an industrial scale using the following methods:

by extraction with ethanol / benzene (separation of terpenes, lipoids, phenols, low molecular weight sugars);

by treatment with caustic soda and sodium sulphide solutions under pressure: soda or sulphate process for cellulose production (solution of lignin, resin and fatty acids; cellulose);