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Plastics Raw Materials, Properties and ProductionPlastics Raw Materials, Properties and Production Most of the plastics we use in everyday life are made from crude oil. The processes involved in turning the oil into the final usable product are complicated but not beyond our scope for understanding. We can gain an appreciation of the intricacies involved in their production through looking at the processes in detail. Combined with knowledge of the environmental issues involved such as pollution caused by in plastic waste, we can develop a strong awareness of our own use and recycling of this precious resource. Plastics: Basic Structure
The easiest way to start viewing plastics is as a chain. Chains are made of very small pieces that are all identical. Put together they make a large structure with great strength. In the case of plastics, the small repeating units are called monomers. Generally, these monomers are based on a compound called Ethene. The monomers join together to form long strands which are called polymers. The different structures of the chemicals involved in making the strands give us the materials we are familiar with and also determine whether a plastic is easily recycled or not. The components of the chain give different properties, as does the types of joins between the chains. There are two main ways the chains are joined: 1: Little Or No Cross Linking In these plastics, the chains mainly lie side by side and are not strongly chemically bonded to one another. These plastics are typically soft and can be stretched out of their original shape. A good example of this is cling wrap, commonly used to cover food.
These forms generally melt when heated. The heat makes the chains vibrate and so puts extra distance between them, which weakens the bonds between the chains and lets them move past one another. This explains why cling wrap becomes more pliable when it has been in the microwave oven for a period of time. These plastics are called thermoplastic because they become more pliable when heated (the original meaning of plastic is "capable of being shaped or formed"). They are the most easily recycled plastics. 2: Lots of Cross Linking These forms have very strong bonds between the different chains. This makes it almost impossible for the chains to slide past each other and result in plastics that are both hard and brittle.
When heated, the chains do not move and tend to burn and char rather than melt. They are technically referred to as thermosetting polymers. These plastics are stronger than the types with little cross linking and are used where strength is the desirable property, such as in the handles of cooking pots. These plastics require a great deal more effort to recycle. Plastics Raw Materials, Properties and Production Return from Plastics Raw Materials to the Green Planet home page for more Solar Power Facts.
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