Fair enough. Never thought of it as a 'type' of plastic. I always think of my aquariums when I hear 'acrylic', never thought of them as plastic.
"Plastics can be classified by chemical structure, namely the molecular units that make up the polymer's backbone and side chains. Some important groups in these classifications are the acrylics, polyesters, silicones, polyurethanes, and halogenated plastics. Plastics can also be classified by the chemical process used in their synthesis, such ascondensation, polyaddition, and cross-linking."