Rubber is a naturally occuring polymer.
It is obtained as latex from rubber trees. It is highly elastic.
It is a polymer of isoprene (2-methyl buta-1,3-diene)
In natural rubber, about 11,000 to 20,000 isoprene units are linked together in a chain like arrangement.
Natural rubber is a thermoplastic. It becomes soft and sticky when heated. It is not hard and tough.
The properties can be modified and improved by the process of vulcanization.