When plastic replaces rubber - The term "plastic" is an awkward way of describing polymers. Usually, from oil or natural gas, they are long-chain molecules, each chain having hundreds of thousands of bonds. These long chains confer interesting physical properties, such as strength and hardness, qualities that short molecules simply cannot provide.

The word "plastic" is a diminutive of the term "thermoplastic", which refers to the polymeric materials that can be formed and deformed by heat. The polymer manufacturing industry was developed in the 1930s. The meticulous work on polyamides led to the marketing of nylon, which replaced during the war the silk used to make women's stockings.

Synthetic polymers are all those made by the human hand in laboratories or on an industrial scale. From a structural point of view, they consist of the union of small units, called monomers, which are linked to the formation of a polymer chain or network.

The polymeric structure of the type "spaghetti" is illustrated in the upper lower section. Each black dot represents a monomer, linked to the other by a covalent bond. The succession of points leads to the growth of polymer chains, whose identity will depend on the nature of the monomer.

Also, the vast majority of its monomers are derived from petroleum. This is done through a series of processes that consist of reducing the size of hydrocarbons and other organic species to obtain versatile and synthetically versatile molecules.

Property
As the possible structures of polymers are diverse, so are their properties. They go hand in hand with the linearity, the branching (absent in the image of the chains), the bonds and the molecular weights of the monomers.

However, although there are structural models that define the property of a polymer and, therefore, its type, most have some properties and characteristics in common.
Some of these are:

- have relatively low production costs, but high recycling costs.

- Due to the large volume that can occupy the structures, they are not very dense materials and, also, very resistant mechanically.

- They are chemically inert or sufficient to withstand acid (HF) and basic substances (NaOH) attack.

- Lack of driving bands; therefore, they are bad conductors of electricity.

According to their properties, synthetic polymers can be classified as:

Thermoplastic
They are linear or slightly branched polymers whose intermolecular interactions can be overcome by the effect of temperature. This results in softening and pouring, making them easier to recycle.

Thermostable
Unlike thermoplastics, thermoset resistant polymers have many ramifications in their polymeric structures. This allows them to withstand high temperatures without deformation or melting, as a result of their strong intermolecular interactions.

Elastomers
These are those polymers capable of supporting external pressure without breaking, deformation, but then returning to its original form.
This is because their polymer chains are connected, but the intermolecular interactions between them are weak enough to give pressure.

When this happens, the distorted material tends to order its chains in a crystalline arrangement, "slowing down" the movement caused by pressure. Then, when it disappears, the polymer returns to its original arrangement.

Fiber
These are polymers with low elasticity and extensibility due to the symmetry of the polymer chains and the high affinity between them. This affinity allows them to interact strongly, forming a linear crystalline arrangement resistant to mechanical work.

This type of polymer is used in the manufacture of fabrics such as cotton, silk, wool, nylon, etc. And also the most useful polymers in our every day life.