In addition polymerisation, the molecules of the same monomer add together on a large scale to form a polymer. The monomers used are unsaturated compounds like alkenes, alkadienes and their derivatives.
Polyethylene, polypropylene, PVC, Acrilan, Buna-S, and polybutadiene are addition polymers.
Terylene, Nylon, and Bakelite are condensation polymers.