Plastics: Fundamentals & Applications

In everyday life we are constantly surrounded by a variety of materials, but no material is as ubiquitous and versatile as plastic. It is light, durable, cheap and can be moulded into any shape imaginable. But what exactly is plastic? How is it manufactured and processed? And what about the recycling of plastic? In this article we want to clarify these questions.

Plastics are polymeric materials that consist of long molecular chains. These chains are composed of many repeating units called monomers. Depending on the type and arrangement of the monomers, plastics can have a wide variety of properties, such as flexibility, hardness, heat resistance, chemical resistance and much more. Plastics can be both natural (e.g. derived from plants) and synthetic (i.e. produced in chemical processes).

The production of plastic takes place in several steps. First, the monomers are produced, often from petroleum or natural gas. These are then combined into polymers in a process called polymerisation. In this process, heat, pressure or catalysts are used to make the monomers form chemical bonds with each other and form long chains. After polymerisation, the plastic is usually further modified, for example by adding additives to achieve certain properties.

There are different methods of processing plastics. Some of the most common are injection moulding, blow moulding, extrusion and thermoforming. In injection moulding, molten plastic is forced into a mould and then cooled to produce the finished part. In blow moulding, a plastic 'preform' is inflated to give the shape of a hollow body. In extrusion, the plastic is forced through a die to produce long parts such as pipes or profiles. In thermoforming, the plastic is heated and then pressed into a mould.

 

Plastic can be recycled in a number of ways. The most common method is mechanical recycling, where plastic waste is collected, sorted, cleaned and then shredded. The shredded plastic pieces are then melted and made into new products. There is also chemical recycling, where plastics are broken down into their individual monomers and then repolymerised.

Although natural plastics such as rubber have been known for thousands of years, the development of synthetic plastics began in the 19th century. The first fully synthetic plastic - Bakelite - was invented in 1907 by Leo Hendrik Baekeland.