PLASTIC



Plastic is made from fractions of natural gas or crude oil changed chemically into a solid form. There are two basic types of plastic: thermosetting and thermoplastics. Thermosetting plastics are set to a permanent shape and cannot be softened. These plastics are used primarily for multiple use items, such as dishes and furniture. Thermoplastics are soft when exposed to heat and pressure and harden when cooled. Thermoplastics are the most common type of plastic and are used to make a variety of products. Some of the most common types of thermoplastics are polyethylene (used to make soft plastic margarine tubs, milk jugs, film, pipes, and tubing), polystyrene (used to make styrofoam, wall tiles, and foam packaging), polyvinyl chloride-PVC (used to make shower curtains, pipes, phonograph records, and insulation), polypropylene (used to make pipes, auto parts, toys, and housewares), and polyethylene terephthalate - PET (used to make soda bottles).

Plastics are produced principally to be used in packaging. There are many toxic chemicals used in the manufacture of plastic packaging. Some of these are benzene, cadmium compounds, carbon tetrachloride, chromium oxide, diazomethane, lead compounds, styrene, and vinyl chloride. These hazardous chemicals are used as solvents, pigments, and catalysts for chemical reactions.

In 1993, plastics accounted for 11.5% of the U.S. municipal waste stream by weight (23.9% by volume). In 1994, plastics comprised 9.5% (by weight) of the waste stream.

Plastic usually does not decay for hundreds of years. However, by altering its chemical make-up, plastic can be made susceptible to photodegradation (break down in the presence of sunlight) and biodegradation (break down by microorganisms). Some states now require six pack plastic holders to be degradable. Unfortunately, there is little known about what happens to the chemical additives, toxic heavy metals, and other ingredients when the plastic degrades.

Incineration is one way to reduce the volume of plastics headed for the landfill. When burned, plastics release more energy than other municipal wastes. However, plastics contribute many pollutants, including heavy metals, to the incinerator's ash and air emissions. In addition, the incineration of PVCs release hydrochloric acid, which can damage plants, buildings, and the incinerator itself.

One way to remove plastic from the waste stream is to recycle it. At least 80% of all thermoplastics could be melted down and made into other products. However, each type of thermoplastic has different physical and chemical characteristics. Because of this, most recycling must be limited to a single thermoplastic type. There is some interest developing for mixed plastics recycling which reprocesses plastics usually considered to be chemically incompatible to produce a range of lumblike products. Although changing rapidly, there are few available markets which accept plastics for recycling. 0.9 million tons of plastics (4.7%) were recycled in the U.S. in 1994.

Another way to reduce the amount of plastics entering the landfill is to reduce the amount of plastic you purchase and throw away. This is known as source reduction.

Here are some suggested ways to reduce plastic consumption in your home:

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