Synthetic fibres are made from polymers, many of which are obtained from petroleum. Some common synthetic fibres are nylon, rayon, terylene, acrylon and cashmilon. They can be placed into two groups.
1. Fibres made from cellulose
2. Fibres made by joining monomers.
Synthetic materials are cheap, strong and attractive for clothing. They are easy to maintain as they are easy to wash, light in weight and resistant to wrinkles, moths and molds. When a new synthetic fibre is developed, it is given a new name by the trade commission. In order to receive such a name, the new product must have useful properties for the consumer.
Manufacture of synthetic fibres
Most synthetic fibres are made by forcing liquids through tiny holes in a metal plate and allowing them to harden. A wide range of liquids produces a great variety of fibres. The metal plates are called spinnerets. They are made of gold or platinum because these metals are not affected by most chemicals. The size of the spinneret is about the size of thimble and it has 10 to 150 small openings, depending on the thickness of the strand wanted. Different synthetic fibres are made from different raw materaials.
It is also called artificial silk. Rayon is made from cellulose. There are several varieties of rayon. Buyt rayon produced by the viscose process is the most important. The ingredients for making viscose rayon are
1. Cellulose (C6H10O5),
2. Sodium hydroxide (NaOH),
3. Carbon disulphide (CS2), and
4. Sulphuric acid (H2SO4).
Manufacture of rayon:
The manufacture of rayon involves the following steps.
1. Cellulose in the form of wood pulp is treated with NaOH.
2. On adding CS2, it dissolves completely and a yellow syrup-like liquid called viscose is formed.
3. Viscose is forced through the fine holes of the spinneret into a solution of dilute H2SO4. Silk-like threads are formed. This product is viscose rayon.
Uses of rayon:
Rayon can be mixed with cotton or wool, which makes it more suitable for our needs. It is a good fabric or sarees. When mixed with cotton it makes a good dress material. Aprons and caps are preferably made of rayon. On mixing it with wool, it serves as a good fibre for making carpets. Bandages and lints for dressing wounds are made of rayon. Hosepipes and conveyor belts are also made from rayon.
Perspiration weakens rayon fibres and they lose strength when wet.
Acetate is another well-known fibre made from wood pulp. The reaction between wood pulp (cellulose) and acetic acid is the basis for this manufacture of this fibre. Acetate is made of fibres that do not wrinkle or shrink as much as rayon. It is an efficient smoke remover, thus it is used in cigarette filters.
Acetate fibres melt when burned. They are destroyed by pressing with very hot iron. Some dry-cleaning solvents dissolve the fibres.
Nylon is a polymer made of polyamide chains. The basic materials for making nylon are coal and petroleum. The polymer is squirted through spinneret holes to form nylon threads. The strands are then stretched four times their original length. The stretching forces the molecules to line up, giving nylon an increased strength and making it more elastic. Nylon is light weight, fine and durable. It is resistant to moths and molds. It absorbs very little water, therefore it dries quickly.
Uses of nylon:
Hammocks, fishing nets tyre cords, ropes, bristles of brushes and parachute fabrics are all made of nylon fibre. As nylon is elastic in nature, it is a good material for making stockings and socks. Nylon sarees are quite common in our country.
Nylon has a few weaknesses, as it absorbs very little moisture it is difficult to dye. It produces static electricity when rubbed. Being a non-cellulose fibre, it requires low to moderate ironing heat.
Acrylic and polyester are non-cellulose fibres. They are manufactured from petroleum products. Terylene and Dacron are examples of polyesters. These fibres are easy to wash; they dry quickly, and resist chemicals and wrinkles. They are difficult to dye. These fibres blend well with natural fibres in making cloth. Terylene is often mixed with cotton to make terycot, with wool, it gives terywool. Clothes made of these are more comfortable to wear than pure terylene.