Complex sentence: Plastics are usually classified by: the chemical structure of the polymer's backbone and side chains; some important groups in these classifications are: the acrylics, polyesters, silicones, polyurethanes, and halogenated plastics.
Split into simpler sentences: Plastics are usually classified by: the chemical structure of the polymer's backbone and side chains. Some important groups in these classifications are: the acrylics, polyesters, silicones, polyurethanes, and halogenated plastics.