Poly soft drink bottles

Soft-drink bottles made from poly(ethylene terephthalate) (PET) are usuady made by stretch-blow mol ding in a two-step process. Eirst, a test-tube-shaped preform is molded, which is then reheated to just above its glass-transition temperature, stretched, and blown. Stretching the PET produces biaxial orientation, which improves transparency, strength, and toughness of the botde (54,56). A one-step process is used for many custom containers that are injection stretch-blow molded. 

Poly (ethylene terephlhalate) L—PET Soft-drink bottles... 

Because the monomers above are all joined by ester linkages, the polymer chain is a polyester. This one is called PET, which stands for poly(ethylene terephthalate). (PET is used to make soft-drink bottles, magnetic tape, and many other plastic products.)... 

Recycling of unwanted polymers is the best solution, and six types of plastics in common use are frequently stamped with identifying codes assigned by the Society of the Plastics Industry (Table 31.2). After sorting by type, the items to be recycled are shredded into small chips, washed, dried, and melted for reuse. Soft-drink bottles, for instance, are made from recycled poly(ethylene terephthalate), trash bags are made from recycled low-density polyethylene, and garden furniture is made from recycled polypropylene and mixed plastics. 

Problem 31.8 Poly(ethylene terephthalate), or PET, is a polyester used to make soft-drink bottles. 

Dacron fiber is used to make fabric and tire cord, and Mylar film is used to make magnetic recording tape. Mylar film is strong, flexible, and resistant to ultraviolet degradation. Aluminized Mylar was used to make the Echo satellites, huge balloons that were put into orbit around the Earth as giant reflectors in the early 1960s. Poly(ethylene terephthalate) is also blow-molded to make plastic soft-drink bottles that are sold by the billions each year. 

Standard plastic soft drink bottles are made of poly(ethylene terephthalate), or PET. In the industrial-scale synthesis of PET, the usual starting materials are dimethyl terephthalate and ethylene glycol (Eigure 10.1). These compounds react to form bis-(2-hydroxyethyl) terephthalate (BHET) and methanol. The methanol boils off at the reaction temperature (typically around 210°C), leaving fairly pure BHET. Then, the BHET is heated further to around 270°C, where it undergoes a condensation reaction to form PET polymer. Ethylene glycol is a byproduct in this second step and can thus be reused within the plant to produce more BHET. 

PET Poly( ethylene terephthalate) Soft-drink bottles, household chemical bottles, films, textile fibers Soft-drink bottles, household chemical bottles, films, textile fibers... 

Plastics in MSW The Americas, in the United States, plastic resin sales and captive use reached 46.2 million tons in 2001, a 4% decrease from 2000, according to the American Plastics Council (1). Resin production rose to 45.9 milUon tons in 2001, up 4.8% from the previous year. The U.S. plastics industry continues to expand into new markets as plastic products come to replace ones made of wood and metal (Fig. 1). In the United States, some 232 million tons of MSW were generated in 2000, an increase of 0.9 million tons over 1999 (Fig. 2). Of this stream, plastics constitute about 10.7 wt%. Plastic containers and packaging dominate, followed by materials in goods such as automobiles, appliances, electronics, furniture, and carpeting. Plastic resins used in containers and packaging include poly(ethylene terephthalate) (PET in soft drink bottles with polypropylene [PP] caps), high density polyethylene (HDPE in milk and water bottles), poly(vinyl... 

One of the more recent applications is the use of amorphous poly(ethylene terephthalate) for soft drink bottles. The major requirements are to keep carbon dioxide and water in and to keep oxygen out. One must realize that these gases are continuously being transported across the plastic even if at a low rate, causing the soft drink eventuaUy to go flat. Thus these drinks have a shelf life, after which they must be discarded if not sold. 

Obtain a two-liter plastic soft drink bottle and measure the thickness of its walls. Assuming it is made of amorphous poly(ethylene terephthalate), what is the estimated length of time for the level of carbonation to decrease by a factor of 2 (Afterward, make sure the bottle is recycled ) Why isn t low-density polyethylene used for this purpose (Pressure in fresh soda bottles is around 4 Atm.)... 

Poly(ethylene terephthalate), or PET, is a polyester used to make soft-drink bottles. It is prepared by reaction of ethylene glycol with 1,4-benzenedicarboxylic acid (terephthalic acid). Draw the structure of PET. 

The water and soft drink bottles made of poly(ethylene terephthalate) that now dominate grocery shelves have almost completely displaced glass bottles. It would come as a surprise to most consumers to find that soft drink bottles, video and audio tapes, and polyester apparel all are made from the same polymer. Likewise, polypropylene used in the casing for almost aU automobile batteries has the same basic formula as the polymer used for indoor-outdoor carpeting, transparent overwrap films, lawn furniture, and polyolefin intimate apparel. 

C. Chen. Study of Glycolysis of Poly(ethylene terephthalate) Recycled from Postconsumer Soft-Drink Bottles. III. Further Investigation. J. Appl. Polym. ScL, 87, 2004-2010 (2003). 

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