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Natural and synthetic polymers
1.With names such as polytetrafluoroethyline and polyethyleneteraphthalate, it is not surpprising that polymers are usually called by by their more common name, plastic. But what, exactly, is a polymer or a plastic? Polymers are compounds made up of several elements that are chemically bound. Most compounds consist of large numbers of tiny molecules, which each contain just a few atoms. For example, a water molecule – H2O – contains two hydrogen atoms and one oxygen atom. But the molecules of polymers contain huge numbers of atoms, joined together in long chains.
2. Rubber, thanks to its many uses from rubber bands to car tyres, is one of the best-known polymers. It comes from latex, a natural liquid which comes from rubber trees. Rubber is therefore a natural polymer. However, most of the polymers used in industry are not natural, but synthetic. The term «plastic» is generally used to refer to synthetic polymers - in other words, those that are manmade.
3. Synthetic polymers can be divided into two main categories. Thermoplastics can be melted by heat, and formed in shaped containers called moulds. Thermosetting plastics, also called thermosets, can be heated and moulded like thermoplastics. They may also be mixed from cold ingredients. However; during cooling or mixing, a chemical reaction occurs, causing thermosets to cure. This means they set permanently, and cannot be moulded again. If a thermoset is heated after curing, it will burn.
Ответьте на вопрос:
Why are polymers usually called plastic?
Plastic usually contains a lot of synthetic polymers.
Polymers are usually called plastic by scientific mistake.
Plastic is a common name for all polymers.
Polymers have very long names which are hard to pronounce.