Answer:
Polymers are the naturally occurring or synthetic macromolecules that are composed of repeating subunits, called monomers.
The three main classes of polymers are: thermoplastic, thermosetting, and the elastomers.
Thermoplastic polymers have linear bonding. These polymers can be melted again and thus can recycled.
Thermosetting polymers have cross-linked bonding. These polymers decompose when heated and thus can not be remelted and recycled.
Elastomers have linear bonding with some cross-linking. These polymers extreme elastic extensibility and thus can revert back to its original shape after deformation, without causing any permanent damage.