Natural polymers can be modified by chemical treatment.
The product obtained after the modification is known as a semi-synthetic polymer. A new polymer is synthesized out of a naturally occurring one and hence the name!
Vulcanized rubber is a semi-synthetic polymer. Rubber in its natural form is not thermally stable. It becomes very hard when it is cold and melts down in heat. But, when treated with sulphur, rubber achieves thermal stability and becomes flexible and can be used to make a range of useful products. This chemical treatment of rubber is known as vulcanization.
Similarly, many other natural polymers can be modified into semi-synthetic polymers with desirable properties.
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