Lignin is a complex chemical compound that acts as a glue binding the fibers of plants and some algae together. It fills the spaces between cellulose, hemicellulose, and pectin in cell walls, providing mechanical strength and rigidity to plants. Lignin is one of the most slowly decomposing components after a plant dies, contributing to the formation of humus. It is stable except when treated with strong alkalis at high temperatures. The structure of lignin is complex and varies, but the main monomers that make it up are p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohols.

1. CW201-WOOD CHEMICAL & MECHANICAL PROPERTIES By Nafizah bt Hassan

2. Lignin is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae A set of non-sugar molecules acting like a glue to hold the fiber together Lignin is chemically bound to carbohydrate materials and occurs throughout the cell wall, being deposited between and within microfibrils during and after the wall - thickening process.

3. Lignin fills the spaces in the cell wall between cellulose, hemicellulose, and pectin components, especially in tracheids and xylem. It is covalently linked to hemicellulose and thereby crosslinks different plant polysaccharides, conferring mechanical strength to the cell wall and by extension the plant as a whole

6. Adhesive of wood binds the fibres provides rigidity and toxicity to the wood Lignin is one of the most slowly decomposing components of dead vegetation, contributing a major fraction of the material that becomes humus as it decomposes.

7. Stable material except when treated with Strong alkali at elevated temperature Stabil in Acid Oxidising agents Mainly located in middle lamella Structure of lignin is complex. The most studied are those of softwood lignin – less complex and variability

8. Problems in pulping Gives color to paper Require stronger chemicals

9. There are three monomers that make up almost all lignin found in nature p-Coumaryl alcohol Coniferyl alcohol sinapyl alcohols

11. p-Coumaryl alcohol is a minor component of grass and forage type lignins. Coniferyl alcohol is the predominant lignin monomer found in softwoods (hence the name). Both coniferyl and sinapyl alcohols are the building blocks of hardwood lignin.