After the First World War, improvements in chemical technology led to an explosion in new forms of plastics.  Among the earliest examples in the wave of new plastics were "polystyrene" (PS) and "polyvinyl chloride" (PVC), developed by the I.G. Farben company of Germany.

Polystyrene is a rigid, brittle plastic that is now used to make plastic model kits, disposable eating utensils, and similar knickknacks.  It would also be the basis for one of the most popular "foamed" plastics, under the name "styrene foam" or "styrofoam."  Foam plastics can be synthesized in an "open cell" form, in which the foam bubbles are interconnected, as in an absorbent sponge, and "closed cell," in which all the bubbles are distinct, like tiny balloons, as in gas-filled foam insulation and floatation devices.

PVC has side chains incorporating chlorine atoms, which form strong bonds.  PVC in its normal form is stiff, strong, heat and weather resistant, and is now used for making plumbing, gutters, house siding, enclosures for computers and other electronics gear, and compact-disk media.  PVC can also be softened with chemical processing, and in this form it is now used for shrink-wrap, food packaging, and raingear.