Plastics can be made in a variety of ways from a variety of materials; shale gas, oil, plants even chicken feathers can all be used to make plastic. Oil derived plastics are the most common. They created from single units, monomers, combined in a variety of ways. This process is called polymerisation. This is why plastics are also often called polymers. And you often find the word poly used in the name i.e. polystyrene.
Different combinations result in different products and there are hundreds of them. They can be used to make everything from varnish to stockings, bottles to car parts by way of varnish, crisp packets and computers. They are cheap, so cheap they can be used to make one use throwaway products like plates and nappies in huge amounts.
Most oil derived plastics are resistant to chemicals, microrganisms and water. They don’t rot. They last for centuries possibly forever. But then there are other plastics that are made in a completely different way, with totally different qualities. Some for instance are truly compostable with a lifespan of months and dissolve in the dishwasher.More are being made everyday.
They have revolutionized the world for the better but are now a major environmental pollutant. We use it everyday for everything even inserting it into our bodies yet we and yet we know very little about it.
This blog explores plastic the product, examines its impact and consider what we should and shouldn’t be using plastic for.
Know what you are looking for? Try the Chapter Index for links to specific posts
Or read the following brief Introduction to plastic
Definition of plastic
If you look in a dictionary you will find that plastic defined as
1. Any of various organic compounds produced by polymerization, capable of being molded, extruded, cast into various shapes and films, or drawn into filaments used as textile fibres.
Basically PLASTIC means flexible. Plastic is used to describe a flexible material. When the word plastic is used to describe a product and not a quality) itcovers a huge range synthetic polymers with massively different qualities.
They look different, they act different and not surprisingly it soon gets confusing.
Polymers & Monomors
Don’t know what polymers are? A polymer is a chain ( poly= many, mer = part) of single units called monomers.
- Natural polymers occur in nature and can be extracted. They include silk, wool, DNA, cellulose, starch and proteins.Synthetic polymers such as plastic are made by scientists and engineers. They too are extracted from natural resources BUT…. though the base material may be a natural product such as oil, the polymers derived from it are not.When building synthetic polymers, the monomors are joined together in new ways, using heat and/or pressure and sometimes a catalyst. Read more here – monomers and polymers
Types Of Plastic
Plastics are divided into thermoplastics and thermoset plastics.
Thermoplastics can be heated and shaped many times.
Thermoset plastics can only be heated and shaped once.
But there is another very important difference. Despite being lumped under the one, all-embracing name, not all plastics are the same.
Some plastics are compostable, (they biodegrade within a certain amount of time).
Most are not biodegradable and last if not for ever, for a very long time.
Where Does Plastics Come from?
Plastic can be made from just about anything BUT most plastics are made from ethane. Ethane can be derived from coal, gas and plants but currently most comes from oil. Ethane based plastics do not biodegrade.
Most plastics then are oil derived and do not biodegrade.
How Oil Derived Plastic Is Made
Most plastics (and we are talking millions of tons each year) are made from naphtha, distilled from oil. These are the most common kinds of plastic and are what is commonly meant by the term. They are used for everything from crisp packets to cars parts to clothes. You can see the process here.
How Bioplastic Is Made
Bioplastics or organic plastics are derived from renewable sources such as starch, vegetable oil and even chicken feathers. Many of these plastics are compostable and biodegradable
Bioplastics are also be made from ethane derived from plants. This is the same as ethane derived from oil and is used in the same way to make the same PET plastics. These plastics are not biodegradable.
Different processes are used to make the various types of bioplastic. You can find links to technical information here. PLA for example is a plastic derived from poly lactic acid that is certified a compostable plastic.
Adding the Addatives
The first stage in plastic production is the polymerization of raw material as above. Once that is done, substances such as fillers and chemicals are added to the base plastic to give color, texture and a whole range of other qualities.
While the polymers used in base plastics are considered harmless, the potential toxicity of the many additives is often unknown while others are thought to be dangerous. Find out more about additives fillers and plasticizers here.
Perhaps the most amazing thing about most plastics is that they don’t rot. While every other thing on the planet is decomposing, plastic remains unchanged. Find out why most plastics don’t biodegrade here.
What’s In A Name
Please note that plastics can be described as compostable, degradable and or biodegradable. Which may seem clear but can be misleading. Many biodegradable plastics do not actually biodegrade.
For more information on the above try the Chapter Index for links to specific posts
Check out this great post by Chris Woodford
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