According to PlasticsEurope, a multinational plastics-industry trade commission, crude oil is distilled into fractions, which are smaller groups of the components that make up oil; some of these fractions are discarded for other purposes, while the ones that are used to make plastics are then further processed. The main fraction of oil that is used for plastic production is known as naphtha.
Crude oil is made up of many different components, with thousands of natural elements mixed together. Not all of these elements are useful for producing plastics. Naphtha and the other crude oil components used for plastic production are then further processed. One of these processing steps is known as polymerization, which uses ingredients like ethylene to convert the chemical structure of the oil fractions, creating long, repeating chains of molecules known as polymers. All plastics are considered to be polymers thanks to this chemical composition.
A wide variety of plastics can be produced from this process, including those that can be remelted and molded, which are known as thermoplastics, and those that retain their shape regardless of heating, which are known as thermosets. Examples of thermoplastics include polyethylene and polystyrene, and examples of thermosets include polyurethane and epoxide.