Wood as a Raw Material

The wood is defined as the main strengthening and water conducting vascular tissue in stem and roots of the plants. Commercial wood generally refers to the solid and homogeneous secondary xylem of the dicotyledons and gymnosperms. The wood is used directly as timber for building purposes, for making furniture, railway sleepers, poles, bridges, ships, boats, carts, bodies of vehicles, musical instruments and sports goods, etc.

It is also used to make boxes, crates, packing cases, toys and agricultural implements. Many industries such as match and paper industries are based on wood products. Besides utilizing the solid timber, other kinds of wood such as plywood, veneers, chipboards, hardboards, cork, etc. are also used for various purposes. The greatest asset of wood is that it is renewable natural resource because of its inexhaustible supply provided its use does not exceed its output.

The wood is the main strengthening and water conducting vascular tissue in stems and roots of plants. Commercial wood generally refers to the solid and homogeneous secondary xylem. The vessels of secondary xylem look like large pores in transverse section. The angiosperms possess vessels. Therefore, the angiospermsous wood is called porous wood. The vessels are absent in gymnosperms, therefore, the gymnospermsous wood is called non-porous wood.

The specific features that make wood unique are as the following:

1. Wood is porous and, therefore it can hold paint, lacquer, varnish and other finishing materials.
2. Wood is considered a better absorber of shock and vibrations.
3. Wood is poor conductor of heat, electricity and sound. Wooden buildings are warm in winter and cool in summer. Change in temperature causes very little change in volume of wood.
4. The form and shape of wood is maintained due to its stiffness.
5. The wood is considered durable if it is resistant against the action of fungi and bacteria. Durability of wood depends upon the presence or absence of infiltrating natural preservatives such as tannin, resin and oil.
6. The weight of wood is different plant species varies due to its different properties of wall materials and of lumen space. The lightest commercial woods are Acacia, Eucalyptus.
7. A wood is considered tough if it is not split off, break off or tear even after a continuous hard work.
8. Presence of large proportion of fiber and fiber tracheids makes a wood strong. A wood may have crushing strength, tensile strength or shearing strength or it may have all the three kinds of strength.

Limitations of woods:

1. The mechanical and physical properties of wood cannot be changed by heating.
2. The wood gets attacked by termites and microorganisms of decay.
3. The wood is combustible and catches fire spontaneously at 275°C.
4. The wood cannot be rolled to get new shapes.