PracticalStudent.com
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Metalwork - Materials - PlasticsPlastics is the general name applied to a range of
"organic polymeric materials" that demonstrate the Property of being Plastic. In
other words what people generally refer to as
"Plastics" should properly be called Polymers,
and that is how they will be reffered to from now on. Polymers are involved in every area of industry
nowadays, from the Food Industry to the Space Program. Since
the production of Polymers really took off, after World
War 2, they have infiltrated every aspect of our everyday
lives. Just walk around your house and notice how many items
are either made from or have parts made from Polymers;
food and liquid containers, the kettle, cables, furniture,
floor coverings, bins, maybe the bath, the list is endless....
Did you notice the variety of shapes, the differing uses,
the varying colours, softness, elasticity....
Below you can see a diagram of the Polymer called Polythene.
You can see what one mer looks like and when a number
of these mers are joined together you have a Polymer. Carbon and Hydrogen are the basis of Polythene,
and most other types of Polymers.
![]() Use the links below to learn more information about Polymers in terms of the types, history, characteristics, uses,
recycling, and much much more.
Categories of PolymersPolymers are divided into 3 main categories, depending on how the are obtained :
Classification of PolymersPolymers are sub-divided into two classification based on their Chemical Bonds, which determines how they react to heat and / or pressure.
The reason that Polymers are affected by heat has to do with their Chemical Bonds. Thermoplastic PolymersThermoplastic Polymers make up 80% to 90% of the worlds Polymers. A Thermoplastic Polymer can be reheated and reshaped over and over again. When enough heat is applied to a Thermoplastic Polymer it softens allowing you to reshape it. It hardens again when it cools. You can learn more about reshaping Polymers in Working with Acrylic . Thermoplastic Polymer's mers are joined by Secondary Bonds. Secondary Bonds break when heated as they are weak and so a Thermplastic Polymer can be reshaped. When the Polymer cools down again tghe Secondary Bond reforms between the mers. Generally Thermoplastic Polymers cannot be used in temperatures much above 100°C as the heat resoftens them. ![]() Thermosetting PolymersThermosetting Polymers, although not as common as Thermoplastic Polymers, are still an important part of the Polymer industry. Thermosetting Polymers undergo a chemical change called curing when they are moulded and hardened. What happens here is that Primary Bonds form between the molecules. Primary Bonds do not break up under heating, so Thermosetting Polymers cannot be resoftened and reshaped. Take the example of boiling an egg. After the egg has been boiled and cooled down, it is solid. If you reheat it the egg will not soften. And that is basically how Thermosetting Polymers operate. Brief History of PolymersNatural Polymers have been in use for thousands of years, however it is really only in the last 140 years that the Polymer Industry has grown.
Rubber had been used by Native South Americans, who used it for shoes,coats and capes, long before Christopher Columbus set off in 1492. In 1770 a British chemist called Joeseph Priestley discovered that Rubber could rub out pencil marks on paper, and this is where the name came from.
After the War the study and production of Polymers rapidly increased to get us where we are today. Common PolymersMost people take Polymers for granted... they all
look the same, they feel the same... etc. Click on Types
of Polymers if you would like to find out more
information about the many common Polymers that
surround you, in terms of discription, properties and uses.
All Polymers are different, and are made in this
way so that they can be used for so many different purposes.
However most most Polymers have the following
charasteristics in common : Recycling of PolymersPolymers have a lot of advantages as their availability and variety of uses prove. However they have one major problem which is very evident in this age of conservation and being friendly to the enviornment. All Polymers have additives included to increase their range of uses and to improve their physical properties. Some additives are :
Polymer ExperimentGoto the Polymer Experiment Page to see how you can differentiate between different types of Polymers in the school workshop. You will need a number of different types of Polymers, and you could even bring some used household products with you to experiment with. Working with AcrylicThe use of Polymers is becoming more and more popular in the Metalwork room. Acrylic or "Perspex" as it is more commonly known is probably the most common. To learn more about workshop techniques with Polymers goto the Working with Acrylic page |
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