Polyvinyl chloride (PVC) is a widely used polymer. Synthesis is fairly simple. Vinyl chloride (C2H3Cl) is mixed with water and a radical initiator is introduced. This forms pellets of differing sizes (depending on reaction conditions), which are melted and molded to form products. Most PVC is used for construction. For applications requiring more flexibility, pthalate additives are used. Softened PVC is used to make IV (intravenous) bags, for example.
PVC by itself is non-toxic, but some of the additives used are toxic and can leech out of the plastic. Several of these compounds are now banned in various countries. In addition the monomer used is known to be carcinogenic. Finally, burning of PVC in some setting leads to dioxin formation, which has known toxic properties.
PVC is also used as a backing for carpet, but a green alternative has been developed by Shaw Industries. The new backing is a new polymer of polyolefin resins, which the manufacturers dubbed EcoWorx. Unlike the PVC backing, the new polymer is recyclable and is made from less toxic starting materials.
http://www.greenchemex.org/?fs=1&id=16&module=resources.edit
Monday, March 02, 2009
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