Category Science

Two main processes are used to produce plastics – polymerization and polycondensation – and they both require specific catalysts. In a polymerization reactor, monomers such as ethylene and propylene are linked together to form long polymer chains. Each polymer has its own properties, structure and size depending on the various types of basic monomers used.

In a polymerization reactor, pressure and heat cause ethylene molecules, mixed with other chemicals, to link together. In ethylene the molecules form a colourless inflammable gas. When the same molecules are linked together in big chains called polymers, the plastic polyethylene or polythene is made — one of the world’s most widely used plastics. Other chemical combinations can produce polymers of different lengths and structures.

Once the polymers have been formed, the hot liquid plastic is taken from the reactor, cooled, and cut into chips or pellets.

• Each molecule of ethylene is made up of two atoms of carbon and four of hydrogen.
• If another chemical, known as a ‘catalyst’, is added these molecules form a long chain. This is called ‘polymerization’.
• Polythene gets its name from ‘poly’ meaning ‘many’.

An oil refinery is an industrial plant that refines crude oil into petroleum products such as diesel, gasoline and heating oils. Oil refineries essentially serve as the second stage in the production process following the actual extraction of crude oil by rigs. The first step in the refining process is distillation, where crude oil is heated at extreme temperatures to separate the different hydrocarbons.

Oil refineries serve an important role in the production of transportation and other fuels. The crude oil components, once separated, can be sold to different industries for a broad range of purposes. Lubricants can be sold to industrial plants immediately after distillation, but other products require more refining before reaching the final user. Major refineries have the capacity to process hundreds of thousand barrels of crude oil daily.

In the industry, the refining process is commonly called the “downstream” sector, while raw crude oil production is known as the “upstream” sector. The term downstream is associated with the concept that oil is sent down the product value chain to an oil refinery to be processed into fuel. The downstream stage also includes the actual sale of petroleum products to other businesses, governments or private individuals.

• Crude oil is piped in and heated. As the different chemicals (or ‘fractions’) in the oil get hotter they start to boil and turn into gases (or ‘evaporate’).
• Each fraction boils at a different temperature. The ones with the lowest boiling points stay as gases for longest. They rise to the top of the column as they cool. The liquids with higher boiling points do not stay as gases for long, so they do not rise far.
• As each gas cools it turns back into a liquid (or ‘condenses’). The condensing liquids are collected at different levels in the column.
• Oil is full of useful chemicals. Did you know we get fuels, soaps, tar and some of the ingredients for drugs from the chemicals in oil?
• Certain fractions are mixed to give plastic making chemicals.

Most plastics come from chemicals in crude oil. However as the world’s a reserve of crude oil begin to run out; coal and gas are now being used more frequently. At a refinery, crude oil is separated into different fractions or chemicals. Most of these fractions are used for fuels.

In a further process at the refinery some of the remaining fractions are cracked or separated into various parts, including the gas ethylene, one of the main chemicals from which plastics can be made.

Plastic is a word that originally meant “pliable and easily shaped.” It only recently became a name for a category of materials called polymers. The word polymer means “of many parts,” and polymers are made of long chains of molecules. Polymers abound in nature. Cellulose, the material that makes up the cell walls of plants, is a very common natural polymer.

Over the last century and a half humans have learned how to make synthetic polymers, sometimes using natural substances like cellulose, but more often using the plentiful carbon atoms provided by petroleum and other fossil fuels. Synthetic polymers are made up of long chains of atoms, arranged in repeating units, often much longer than those found in nature. It is the length of these chains, and the patterns in which they are arrayed, that make polymers strong, lightweight, and flexible. In other words, it’s what makes them so plastic.

These properties make synthetic polymers exceptionally useful, and since we learned how to create and manipulate them, polymers have become an essential part of our lives. Plastics have saturated our world and changed the way that we live.

Plastics are everywhere! You are sitting on a plastic chair, leaning on a plastic-coated table or wearing plastic shoes. There are many different types of plastics. So what makes something a plastic? The first plastics were made more than 100 years ago from cellulose which is naturally found in plants.

Today plastics are made mostly from crude oil, a raw material that is fast running out. In the future, new raw materials must be found to make plastics, and there must be greater recycling of plastic waste.

Plastics is the term commonly used to describe a wide range of synthetic or semi synthetic materials that are used in a huge and growing range of applications. Everywhere you look, you will find plastics. We use plastic products to help make our lives cleaner, easier, safer and more enjoyable. We find plastics in the clothes we wear, the houses we live in, and the cars we travel in. The toys we play with, the televisions we watch, the computers we use and the DVDs we watch all contain plastics.

Plastics are organic materials, just like wood, paper or wool. The raw materials used to produce plastics are natural products such as cellulose, coal, natural gas, and salt. Plastics have become the modern material of choice because they make it possible to balance today’s needs with environmental concerns.

• The word plastic comes from the Greek Plastikos – meaning able to be shaped.
• They can be shaped into almost anything.
• Plastics are light and relatively cheap.
• They can be produced in different colours.
• Heat and electricity do not travel through plastics easily; they are good ‘insulators’.
• Unlike metals and wood, they do not rust or rot.

But plastics do have some disadvantages too.

• They are made from resources which will eventually run out, and they are difficult to recycle.
• Because they do not naturally rot (biodegrade) like wood, they are an eyesore and a hazard in the environment.
• They are not as strong as many metals and they melt at high temperatures, sometimes giving off poisonous fumes.