Chlorinated Hydrocarbons

Organic polymer materials are prevalent in our modern society. The common term plastic really refers to synthetic organic polymer materials consisting of long carbon chains. One of the best known polymers, home plastic wraps used to cover food, is polyethylene. For use as plastic food wrap, polyethylene is prepared as a thin sheet. A greater thickness of polyethylene is used to mold plastic houseware products, like plastic buckets, carbonated drink bottles, or brush handles. Another common and closely related polymer is polypropylene. In addition to also being used for similar products, polypropylene is used to make clothing, the fibers of which are woven synthetic polymer strands. Both polypropylene and polyethylene are used extensively. As chemicals, though, they are classified as hydrocarbons. The chemical addition of chlorine atoms into the molecular structure of hydrocarbon polymers gives the polymers different useful properties. Organic polymers containing chlorine are called chlorinated hydrocarbon polymers.

Perhaps the best known chlorinated hydrocarbon polymer is Polyvinyl Chloride, or PVC. Because PVC also contains atoms of chlorine incorporated into the polymer molecule structure, it has different uses than polyethylene or polypropylene. PVC polymer molecules are created by chemically linking monomers of vinyl chloride molecules into very long chains. Vinyl chloride is a two carbon molecule unit, also containing chlorine. The polymer structure is very similar to polyethylene. Vinyl chloride is made from the addition of chlorine to ethylene with hydrochloric acid as a byproduct. In the United States, about 15% of all ethylene is used in PVC production.

PVC was first discovered as a polymer in 1872 when sealed tubes containing vinyl chloride were exposed to sunlight. The solution inside the tubes polymerized into PVC. In the United States, the first patents for the industrial production of PVC were submitted in 1912, making PVC one of the earliest plastics in use. The prevalence of PVC and its importance to our everyday lives is immense. To name just a few products made, PVC is found in pipes for household plumbing and waste management, phonograph records, soles and heels of shoes, electrical wire insulation, coated fabrics like Naugahyde, plastic films like Saran Wrap, patio furniture, vinyl floor tiles, novelty toys, yard fences, home siding, and credit cards. Its properties make it very useful in making many of the products that we take for granted each day. PVC is inexpensive to synthesize relative to other polymers, making it an attractive material to use.

Because the polymer molecules of PVC are able to fit closely together, they prevent the seepage of fluids through the plastic. Therefore, PVC has important advantages over other organic polymers in clean water transport, preventing food contamination, and securing sterile products. For instance, PVC blood bags allow blood products to be stored longer than do glass containers while allowing for flexibility. PVC packaging protects fresh food from deterioration, and PVC pipes and liners provide safe drinking water supplies from reservoirs, preventing contamination during transport.

PVC is also fire retardant, making it a very safe chlorinated hydrocarbon polymer. Because they are derived from petroleum products, organic polymers are often very flammable. PVC, however, is difficult to ignite. When PVC is burned, it releases less heat than other materials. PVC is used to insulate cables that can build up heat because of its heat resistant property. Additional safety characteristics of PVC include its durability and shatterproof qualities. Therefore, PVC is used to make protective eyewear, shatterproof bottles, life jackets and inflatable personal flotation devices. The durability and corrosion resistance of PVC makes it useful in auto underbody sealing, gutters, window frames, shutters, and cladding of homes.

In addition to the previously listed uses, PVC is an important polymer because it requires less energy to manufacture than other plastics, and can be recycled in to new products after first use. Other closely related chlorinated hydrocarbon polymers include polychloroethylene, and trichloroethylene.

A very important example of a chlorinated hydrocarbon polymer that is a synthetic rubber is polychloroprene. Polychloroprene is an example of an elastomer, or polymer that has the elastic properties of rubber. Along with butadiene, isoprene, and styrene, polychloroprene accounts for 90% of all worldwide synthetic rubbers produced. Closely related in chemical structure to natural rubber extracted from rubber-tree plants, polychloroprene is used to make hoses, belts, shoe heels, and fabrics because it is resistant to corrosive chemicals.