Polymers

Introduction

A polymer is a big molecule or macromolecule that consists of a large number of components. The Greek word for “many parts” is “polymer“. We live in a world filled with polymers. DNA is a naturally occurring biopolymer, and polypropylene, which is widely used as plastic around the world, is derived from it.

Polymers can be found in nature (natural polymers) or man-made (synthetic polymers). Because of their various physical and chemical properties, polymers are widely used in daily life.

Types of polymers

There are many different types of polymers that can be made through polymerisation, which involves reacting monomers to generate polymer chains, i.e. 3-dimensional networks that form the polymer links.

Depending on the functional groups connected to the reactants, a polymerisation mechanism can be selected. Almost all macromolecules in the biological setting are either entirely polymeric or comprise massive polymeric chains.

Classification of polymers

Because of the wide range of uses and diverse properties of polymers, they are unable to be grouped into a single category. Polymers can be categorised based on the following factors.

1. Polymers categorised by source of availability

Natural, synthetic and semi-synthetic polymers are all types of polymers that fall into this group.

• Natural polymers

They can be found in plants and animals, and they are naturally occurring. Proteins, starch, cellulose and rubber are just a few examples. Biopolymers, which are biodegradable polymers, are another option.

• Synthetic polymers

Polymers created by humans are used in this product. Synthetic polymer plastic is the most frequently used and most prevalent. There are numerous uses for it, including in the dairy industry and the production of a variety of products. Nylon-6,6, polyethers, etc., are a few examples.

• Semi polymers

They are made from natural polymers that have been chemically altered. Cellulose nitrate and cellulose acetate are two examples.

1. Polymers categorised based on the monomer chain structure

The following subcategories are included in this category:

• Linear polymers

Polymers with long and straight chains fall under this group. PVC, or polyvinyl chloride, is a linear polymer that is commonly used to make pipes and electric lines.

• Branched-chain polymers

Branched-chain polymers are defined as those in which the linear chains of a polymer form branches. Low-density polythene is one example.

• Cross-linked polymers

They are made up of monomers that are either bifunctional or trifunctional. Linear polymers have a stronger covalent bond than branched polymers. Examples of this type of material include bakelite and melamine.

Other ways of classification

Polymerisation-based classification

Addition polymerisation:

Chain growth polymerisation is another name for this process. Small monomer units combine to generate a massive polymer in this case. The chain lengthens with each new step. Polymerisation of ethane in the presence of peroxides, for example

Condensation polymerization

During condensation polymerisation, tiny molecules including water, carbon dioxide and nitrate are destroyed (step-growth polymerisation). Bifunctional organic molecules such as idols, diols, diamines, dicarboxylic acids typically undergo polymerisation reactions of this type. Preparation of Nylon 6, for example. 

• Monomers-based classification

Homomer:  In this type, a single type of monomer unit is present. For example, Polyethene

Heteropolymer or co-polymer: It consists of different types of monomer units. For example, nylon -6, 6

• Molecular force classification

Elastomers: This type of material is similar to a rubber-like substance. However, it has a far lower level of interactivity. Rubber is an example.

Fibres: High tensile strength and strong interaction forces characterise fibres. Nylon -6, for instance.

Thermoplastics: There are intermediate forces of attraction in thermoplastics. Polyvinyl chloride, for example.

Thermosetting polymers: The mechanical characteristics of a material can be considerably improved with the use of thermosetting polymers. It is more resistant to chemicals and heat. Many of the most common materials used in the construction industry are examples of these materials.

Structure of polymer

Hydrocarbons make up the majority of the polymers we encounter. The tetravalent property of carbon allows for a lengthy chain of connected carbon and hydrogen atoms to form a hydrocarbon backbone.

Polypropylene, polybutylene and polystyrene are examples of hydrocarbon backbone polymers. There are also polymers that have other elements in their backbone instead of carbon. Nylon, for example, has nitrogen atoms in the repeating unit backbone of the material.

Physical properties

The physical properties of polymers are:

• The tensile strength of a polymer improves as the chain length and cross-linking increase.
• A polymer is not melted but rather changes its state from crystallisation to semi-crystalline crystallisation.

Chemical properties

The chemical properties of polymers are :

• Hydrogen and ionic bonding in the polymer improve cross-linking strength compared to that of ordinary molecules with various side molecules.
• The polymer’s dipole-dipole bonding side chains allow it to be extremely pliable.
• The low melting point of polymers with Van der Waals forces joining chains makes them known as weak polymers.

Uses of polymers

Polymers are used in a variety of ways in our daily lives.

• Polypropene is used in a wide number of fields, including textiles, packaging, stationery, plastics, aircraft, construction, rope and children’s toys.
• In the packaging sector, polystyrene is one of the most commonly used plastics. Polystyrene is utilised in a wide variety of everyday items, including bottles, toys, containers, trays, disposable glasses and plates, and television cabinets and lids. Insulation is also one of its common applications.
• Polyvinyl chloride (PVC) is mostly used to make sewage pipes. Electric cables incorporate it as an insulator as well.
• In addition to being used in apparel and furniture, polyvinyl chloride is also becoming increasingly popular in the manufacture of doors and windows. Vinyl flooring is another of its common uses.
• Adhesives, moulds, laminated sheets and unbreakable containers can all be made with urea-formaldehyde resins.
• There are many uses for glyptal in the paint and lacquer industries.
• Bakelite is used to make electrical switches, food products, toys, jewellery, weapons, insulators, computer discs and numerous other products.

Conclusion

A polymer is a chemical substance that has molecules linked together in lengthy, repetitive chains. Polymers offer a wide range of applications because of their unique structure.

Both man-made and natural polymers are widely available. It has been used for millennia in the form of  rubber, a naturally occurring polymeric substance. Mother nature constructed a molecular polymer chain that gives it exceptional elasticity. Shellac, a resin generated by the lac bug in India and Thailand, is another natural polymer that is utilised as a primer, sealer and varnish in the painting industry.

Cellulose, an organic molecule found in plant cell walls, is the most prevalent natural polymer on the planet. Paper, textiles and other materials such as cellophane are all made from it.