Synthetic Fibres and Plastics

A fibre is a thin, thread-like strand from which yarn and fabrics are made. Based on their source, fibres are of two kinds.

• Natural fibres are obtained from plants and animals — for example cotton and jute (from plants) and wool and silk (from animals).
• Synthetic (man-made) fibres are made by human beings in factories from chemicals obtained mostly from petroleum (a substance called petrochemicals).

A synthetic fibre is made of very large numbers of small units joined together in a long chain. Each small unit is a monomer, and the long chain made of many monomers is a polymer (poly = many, mer = part). So a synthetic fibre is a polymer. Interestingly, many natural materials are polymers too — cotton is a polymer called cellulose.

Synthetic fibres have become very popular because they are usually strong, cheap, durable and easy to wash and dry, and they do not wrinkle easily. This is why they are widely used for clothing and many other products.

There are several important synthetic fibres, each with its own properties and uses.

• Rayon — made from wood pulp (a natural source), so it is a partly man-made fibre, also called artificial silk. It is cheap, has a silk-like shine, and is used for clothes and bedsheets.
• Nylon — the first fully synthetic fibre, made without any natural raw material. It is very strong, elastic and light, and is used in socks, ropes, tents, parachutes, seat belts, toothbrush bristles and fishing nets. Nylon is so strong that a nylon thread can be stronger than a steel wire of the same thickness.
• Polyester — made of repeating units of an ester. It does not crease (wrinkle) easily, so it stays neat and is ideal for dress material. A popular polyester is Terylene; PET (used to make plastic bottles) is also a polyester. Terycot and Terywool are made by mixing polyester with cotton or wool.
• Acrylic — a synthetic fibre that resembles wool. Clothes such as sweaters and blankets made from acrylic are cheaper and more durable than those made from natural wool.

Fibres are often blended (mixed) — for example polyester with cotton (polycot) — to combine the good qualities of both.

Plastic is also a polymer, like synthetic fibre. In some plastics the units are arranged in a straight line; in others they are joined in a cross-linked (網-like) pattern. Based on how they behave on heating, plastics are of two kinds.

• Thermoplastics — plastics that soften on heating and can be bent and remoulded again and again. Examples: polythene (used in bags) and PVC (used in pipes, toys, bottles).
• Thermosetting plastics — plastics that, once moulded by heat, cannot be softened or remoulded. Examples: bakelite (used in electric switches and handles of utensils because it is a poor conductor of heat and electricity) and melamine (used for floor tiles and unbreakable crockery).

Plastic is useful because it is light, strong, durable, cheap, a poor conductor of heat and electricity, and does not react with air, water or many chemicals (so it does not rust). This is why it is used for buckets, bottles, packaging, insulation of wires and even in cars and aeroplanes.

But plastic causes a serious problem: it is non-biodegradable — it is not broken down by natural processes, so it stays in the environment for a very long time, polluting land and water and harming animals that swallow it. We should follow the 4 R’s — Reduce, Reuse, Recycle and Recover — and avoid single-use plastic to protect the environment.