Wood pulp is chemically treated to produce a fibre known as Rayon. Rayon is a type of semi-synthetic fibre that is made from cellulose, which is derived from wood pulp. It is often considered as a natural fibre because cellulose is a natural polymer found in plant cells.

The process of making Rayon involves several steps:

1. Extraction of Cellulose: Wood pulp is obtained from trees through a process called pulping. The wood is mechanically or chemically broken down into small fibers, and the lignin, a natural glue-like substance that holds the fibers together, is removed.

2. Dissolving the Cellulose: The wood pulp is then dissolved in a chemical solution, typically sodium hydroxide, to create a thick, viscous liquid called viscose. This process is known as the viscose process.

3. Filtering and Aging: The viscose is filtered to remove any impurities and then aged for a specific period of time. During this aging process, the cellulose molecules rearrange and align themselves to form a more stable and uniform structure.

4. Extrusion: The aged viscose is extruded through fine holes to form filaments. These filaments are then solidified by passing them through a solution of sulfuric acid, which converts the viscose into a solid form.

5. Spinning and Finishing: The solidified filaments are spun into yarns, which can be further processed to create different types of Rayon fibers, such as viscose Rayon, modal Rayon, or lyocell Rayon. The Rayon yarns can be woven or knitted into fabrics and then finished with dyeing, printing, or other treatments.

Rayon is known for its soft, smooth texture, high absorbency, and breathability. It can imitate the appearance and drape of natural fibers like cotton, silk, and wool, making it a versatile material for various textile applications. Rayon fabrics are commonly used in clothing, upholstery, beddings, and other textile products.

In conclusion, the fibre made up by the chemical treatment of wood pulp is Rayon. It is a semi-synthetic fibre derived from cellulose and is produced through a multi-step process involving the extraction and dissolution of wood pulp, filtering, aging, extrusion, spinning, and finishing.