Policloreto

Policloreto, commonly known as polyvinyl chloride (PVC), is a synthetic polymer produced from vinyl chloride monomer (VCM). It is one of the most widely used plastics, available in rigid and flexible grades. Rigid PVC (uPVC) is stiff and strong, while flexible PVC results from the addition of plasticizers, which lower its glass transition temperature and increase flexibility.

Production and properties: PVC is formed by free-radical polymerization of vinyl chloride, typically via suspension or emulsion processes. The polymer contains about 57% chlorine by weight, a factor that contributes to its flame retardancy and chemical resistance. Rigid PVC offers high stiffness and dimensional stability, good electrical insulation, and low cost. Flexible PVC accommodates a wide range of formulations for softness and durability. Processing methods include extrusion, injection molding, calendering, and film or sheet production. PVC is generally resistant to many acids, bases, and salts but can release hydrochloric acid when exposed to high heat, especially during combustion. Stabilizers and additives (such as calcium-zinc, organotin, or historically lead-based stabilizers) are used to improve heat stability and UV aging performance. Plasticizers influence flexibility and aging characteristics.

Applications: PVC is widely used in construction for pipes, fittings, window profiles, and vinyl siding; in electrical cables and insulation; in flooring, medical devices, and packaging films; and in consumer goods. Chlorinated PVC (CPVC) variants offer higher temperature resistance for hot-water systems.

Environmental and safety considerations: production involves vinyl chloride monomer, a substance associated with health risks; end-of-life management includes mechanical recycling and energy recovery, while additives can complicate recycling. Incineration can release hydrochloric acid and other pollutants, requiring controlled disposal and regulatory compliance.

History: PVC was first prepared in the 1830s and achieved commercial development in the early to mid-20th century, with notable work by Waldo Semon and the B.F. Goodrich Company advancing plasticized PVC.