Natural Rubber

Natural Rubber is a stretchable and shrinkable polymer. It is found in nature and can also be artificially synthesised. Humans have been using rubber since the earliest times. However, it became an important industrial raw material for several purposes during the nineteenth century.

It contains impurities and is reactive to environmental conditions and hydrocarbons. The process of vulcanisation increases the physical properties of natural rubber. The high tensile strength of vulcanised rubber makes it more resistant to swelling and abrasion and provides increased elasticity over wide temperature ranges.

Rubber’s elasticity is due to the rejoining of the chains after they have been pulled apart and released. Natural rubber possesses impurities and is vulnerable to environmental conditions and hydrocarbons.

Polymers

Molecules with high molecular mass, usually between 103u and 107u, are called polymers. These are further made of small units which combine to form large polymer units. These repeating units are often called monomers and are linked together by covalent bonds. Polymers are also called macromolecules. Polythene, nylon 66, Bakelite, rubber, and other materials are examples of polymers.

Types of Polymers

Polymers are divided into three categories based on their structure. The three types of polymers are linear chain polymers, branched-chain polymers, and cross-linked polymers.

Linear chain polymers: 

The monomer units are joined together to form straight chains in this arrangement. These longer chains are stacked one above the other and crammed into a tight space. High density, tensile strength, melting, and boiling points arise from the compact packing. Polyethene with a high density is an example of this kind. 

Branched-chain polymers: 

In this type of polymer, monomer units are bonded to form lengthy chains. The long chains are also attached to other chains of various lengths, which are present on the sides of the main long chains. These polymers are loosely packed as a result of branching. Loosely packed branches result in low melting and boiling points, low densities, and lower tensile strength. Polyethene is an example of this type.

Cross-linked polymers: 

Cross-linked polymers are macromolecules in which the polymer molecules are linked by covalent bonds. The monomer units in these polymers, also known as network polymers, are joined together to produce a three-dimensional network.

Rubber Variants

Rubber can be classified into two types based on where it originated from:

1. Synthetic rubber and 

2. Natural rubber 

Synthetic rubber is a polymer created artificially. Different petrochemicals are used to produce it under regulated conditions. Many different forms of synthetic rubber have been produced using petrochemicals.

 Although synthetic rubber’s fundamental monomer unit can be 2-chloro-1,3-butadiene or 1,3-butadiene, neoprene is a synthetic rubber made up of the chloroprene monomer unit. As a result, distinct monomer units exist in all synthetic rubbers.

Natural rubber is a polymer made up of the organic component isoprene, extracted from the bark of tropical and subtropical trees. Latex is a milky colloidal emulsion of rubber, proteins, fatty acids, resins, and water. Latex is derived from the tree, Hevea Brasiliensis.

Natural Rubber as Cross-linked Polymer

A cross-link is a link that connects two polymer chains. Ionic or covalent bonds can be used to form these cross-links. These cross-links can be formed during or after the polymerisation process. Cross-linked polymers are macromolecules with covalent bonds linking the polymer molecules. Cross-linking creates a stable and stronger polymer material because cross-links between polymer chains are stronger than normal intermolecular attractions. Synthetic polymers and naturally occurring polymers both contain cross-linked polymers.

Structure Of Natural Rubber

Isoprene is the monomer unit found in natural rubber. 2-methyl-1,3-butadiene is the chemical name for isoprene, which is a colourless, highly flammable liquid. It has two double bonds. As a result, it is a hydrocarbon that is unsaturated.

Natural rubber is a polymer, which means it’s a long, chain-like molecule with repeating subunits or monomers. Natural rubber’s chemical name is polyisoprene. Isoprene is the monomer (meaning “one-part”) from which it is made.

Natural rubber is a 1,4 isoprene polymer with a linear structure (2-methyl 1-1,3-butadiene). The original double bonds between carbon 1 and carbon 2, carbon 3 and carbon 4 in isoprene are moved between carbon 2 and carbon 3 in natural rubber. One unit’s carbon 1 is attached to another unit’s carbon 4, and so on. Because all the double bonds in rubber are cis, it is referred to as 1,4 polyisoprene. The cis-polyisoprene molecule is coiled and is made up of many chains linked together by weak van der Waals interactions and the least intermolecular forces. As a result, it has elastic qualities and can be stretched like a spring.

Uses of natural rubber

Natural rubber is utilised in applications that undergo high decrement and need heat insulation. Natural rubber is employed in technical applications such as anti-vibration mounts, mattresses, springs, souls of shoes, and bonding material because of its strength and compressibility. However, due to its strength and heat resistance, the majority of natural rubber, about 50 percent, is used in high-geared tyres for race cars, buses, and aircraft. Pipes, auto parts, foam, and battery boxes utilise natural rubber.

Conclusion

Natural Rubber is a type of elastomer polymer that suggests that it can return to its original shape even though it’s stretched. At high temperatures, natural rubber becomes soft, while at low temperatures, it becomes brittle. Vulcanisation is employed to enhance the physical qualities of rubber. Finished rubber has higher endurance, i.e., a smaller amount susceptible to swelling and abrasion, and is more elastic throughout a wider temperature range.