The birth of polyvinyl chloride, or PVC or vinyl as it is better know to the public, dates back to a German patent in the 1910s, but it was not until the late 1920s that a technically useful product was introduced in the U.S. By the start of World War II, the significance of plasticizing PVC (that is, adding a chemical known as a plasticizer to make PVC flexible and processible) was fully realized. It was during the war that the real importance of this polymer became apparent when, due to the acute shortage of rubber, many companies turned to PVC and began to realize its advantages. Because of its wide use in applications that are close to consumers, such as upholstery, flooring, wall coverings, pipe, siding, apparel and accessories, vinyl is one of the better-known plastics. Vinyls are used mainly for their chemical and weathering resistance, high dielectric properties, or abrasion resistance. Vinyl is also dip molded into gloves, slush molded into boots and foamed to make calendered flooring, leather-like upholstery, shoe fabrics and carpet backing. Vinyls are thermoplastic resins produced by the polymerization of the gas vinyl chloride [CH2CHCl]. Under pressure, vinyl chloride becomes liquefied and is polymerized by one of four basic processes: suspension, emulsion, bulk, or solution polymerization. The pure polymer is hard, brittle and difficult to process, but it becomes flexible when plasticizers are added. A special class of PVC resin of fine particle size, often called dispersion grade resin, can be dispersed in liquid plasticizers to form plastisols. The addition of a volatile diluent or a solvent to the plastisol produces an organosol. Copolymers with vinyl acetate, vinylidene chloride, and maleate and fumarate esters find commercial application.