The term “polymer” is composed of two words, (polus, meaning “many, much”) and (meros, meaning “parts”), and refers to a molecule whose structure is composed of multiple repeating units, from which originates a characteristic of high relative molecular mass. The units that make up these polymers are known as polymer.
Polymerization is of two types:
- Addition polymerization
- Condensation polymerization or step growth polymerization.
- Addition Polymerization:
- Condensation Polymerization:
Addition polymerization occurs due to addition reaction when monomers bond together without losing any atom. This happens with monomers having double bonds. During the reaction, the double bonds open, creating a continuous long chain of polymer. Addition polymerization is widely used in chemical industries for creating synthetic polymers like polyethylene, (used in food packaging and manufacture of plastic bags).
Condensation polymerization occurs when monomers join together but with the elimination of a by-product, (usually water). A great example of condensation polymerization is the polymerization of nylon from monomers with carboxylic acids and basic amines. The reaction creates a link between each monomer and produces water as a by-product and is used to produce nylon fibers for clothing.
Types of Polymers:
Polymers are of two types; natural and synthetic polymers.
Natural polymers occur naturally from plants and other renewable resources. Natural polymers include amber, wool, silk, rubber, cellulose, protein etc. The most common natural polymer is DNA, which is the most basic constituent of the human body. The DNA molecule is made of monomers called nucleotides. The monomers are linked by condensation reaction so that many nucleotides are linked in a chain to make the DNA polymer molecule. All natural polymers are environmental friendly and are very important in our lives.
Synthetic polymers are man-made polymers. They are classified into four main categories: thermoplastics, thermosets, elastomers and synthetic fibers. They are commonly found in consumer products such as plastic bags, electrical devices, pipes, super glue etc.
Some most common synthetic polymers include Bakelite, nylon, neoprene, polyvinyl chloride, polystyrene, polypropylene, LDPE, HDPE etc. Synthetic polymers are not biodegradable. This means that they cannot be broken down by micro-organisms, so they may last for many years in garbage causing pollution.
Uses of Polymers:
Both natural and artificial polymers are used in our everyday lives. Natural polymers like carbohydrate, protein, lipids and nucleic acids are all essential part of our diet and must be taken on a regular basis. Cellulose is the main component in the manufacture of wood and paper. Cellulose is also used as a raw material for the manufacture of plastics. Silk and wool are used to make clothes for us.
Synthetic polymers are used in industries to manufacture household and other consumer products. LDPE is used to manufacture toys, flexible pipes, insulation covers (electric wires). HDPE is used for inner insulation of coax cable and for manufacture of plastic bags. Polypropylene is used in auto parts, food packaging and textiles. Polystyrene is used to make plastic cutlery. Polyvinyl chloride is used in fencing, vinyl flooring and electrical insulation. Bakelite is used to manufacture sockets and electrical devices. Nylon is used in fabrics and toothbrushes. Thus polymers have great importance in our lives and without them life would be unimaginable.