Common Plastic Water Bottle
What is polyethylene terephthalate?
The common plastic water bottle is made out of polyethylene terephthalate, also known as PETE. PETE can also be referred to as plastic number one, according to the Resin Identification Coding System. PETE has many uses, including as a textile and in cosmetics. However, it is most commonly used as a container. This is the type of PETE that will be examined below.
Chemical and Physical Properties of PETE:
The chemical formula for PETE is (C10H8O4).
PETE’s technical IUPAC name is poly(ethylene terephthalate).
PETE is combustible, but can release toxins when burned.
PETE will react with strong oxidizing agents and strongly alkaline materials.
For a complete list of PETE’s reactivity, visit this link:
PETE exists as a solid at room temperature. Its melting point is approximately 250 degrees Celsius, and it's boiling point is 350 degrees Celsius. PETE begins to soften at 70 degrees Celsius.
PETE can be transparent or opaque, depending on its crystal structure.
PETE is rigid, lightweight, strong, and non-brittle.
PETE has a smooth texture, with a low coefficient of friction.
PETE is odorless.
PETE is non-soluble.
PETE is non-malleable.
PETE is a barrier to moisture and gas.
Manufacturing Process and Energy Sources:
PETE is created by reacting monoethylene glycol (MEG) with purified terephthalalic acid (PTA). The first step is to mix the MEG with the PTA. They then go through the process of esterification. This is the reaction of an alcohol with an acid, which creates an ester and water. The product from this reaction is sent through pre-polycondensation, and eventually polycondensation. The final polyester is then processed into chips.
Once the PETE has been made, the bottle manufacturing process can begin. The PETE is heated and molded into the shape of a long tube. This tube, called a parison, is placed into another, bottle shaped, mold. A think rod is inserted into the parison, and fills it with highly pressurized air. The combination of pressurized air, heat, and pressure forces the parison to be blown and stretched into the mold. It now has the bottle shape. At this time, a separate plastic piece is attached to the bottom of the bottle. This is to ensure that the bottle stands flat. Once the bottle has been cooled, it can be removed from the mold. Excess plastic is trimmed, and the bottle is ready to be filled.
Although some water bottles are made from recycled materials, the large majority are produced by virgin PETE. Researches have found that it takes roughly 3.4 megajoules of energy to produce one 1-liter bottle. According to some estimates, in 2006, Americans bought over 31 billion liters of water. 900,000 tons of PETE was needed to bottle that water. PETE is manufactured using primarily fossil fuels. This consumption required 106 billion megajoules of energy, or more than 17 million barrels of oil. In addition, production created over 2.5 million tons of carbon dioxide. Finally, 3 liters of water were used in the process of creating just one one-liter bottle.
Likely Fate at the End of its Life:
At the end of its life, a plastic water bottle is most likely to end up in a landfill. In 2005, approximately 2.76 million cubic yards in landfills were taken up by plastic water bottles. Although PETE is recyclable, only about 24% of bottles sold end up in the recycling. PETE does not decompose, and incineration releases toxins into the atmosphere. In addition to ending up in a landfill, a bottle may end up in the ocean. A giant mass of plastic twice the size of Texas floats in the Northern Pacific Ocean.
Safety and Ease of Use, Price, Packaging, and Marketing Strategies:
Water bottles are relatively safe to use. However, it is unwise to reuse PETE bottles as they may retain bacteria. Chemicals can also leech into the water when left for long periods of time, or when heated. Bottles can cost anywhere from less than 50¢ to over $10, depending on the brand and size. Marketing strategies can range from focus on green-ness, to age of consumer, price, or design.
Relative "Green-ness" and Desirability of the Regular Water Bottle:
Water bottles are desired out of the want for convenient water, not from an actual desire for the bottle. Demand is huge for transportable, readily available water. However, the bottle itself is helping no one. The average water bottle uses up resources, and then sits in a landfill. It is marketed as green, because it is recyclable. However, few bottles actually end up in the recycling. Therefore, it is time for a bottle that actually makes the consumer feel good about their purchase. It is time for an ecobottle!