When two or more different monomers are allowed to polymerise together the product formed is called a copolymer, and the process in called copolymerisation. Example, Buna-S and Buna-N, Buna-S is a copolymer of 1,3-butadiene and styrene while Buna-N is a copolyer of 1,3-butadiene and acrylonitrile.
