Plastic Soft Drink Bottles

Acrylonitrile copolymers (typically referred to simply as polyacrylonitrile, PAN) were, in fact, the first bottles introduced by Coca Cola. A suspected issue with monomer extractables developed with the PAN, and it was pulled from the market. PET moved into the business, and dominates today even though the extractables problem was eventually shown to be a nonissue. The damage was done, and PAN never became a player in the market for CSD. 

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A two-liter plastic soft drink bottle can withstand a pressure of 5 atm. Half a cup (approximately 120 mL) of ethyl alcohol, C2H5OH (d = 0.789 g/mL), is poured into a soft drink bottle at room temperature. The bottle is then heated to 100°C (3 significant figures), changing the liquid alcohol to a gas. Will the soft drink bottle withstand the pressure, or will it explode ... 

Esters are widely used in industry as solvents. Ethyl acetate is a good solvent for a wide variety of compounds, and its toxicity is low compared with other solvents. Ethyl acetate is also found in household products such as cleaners, polishes, glues, and spray finishes. Ethyl butyrate and butyl butyrate were once widely used as solvents for paints and finishes, including the butyrate dope that was sprayed on the fabric covering of aircraft wings to make them tight and stiff. Polyesters (covered later in this section and in Chapter 26) are among the most common polymers, used in fabrics (Dacron ), films (VCR tapes), and solid plastics (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. Polyethylene terephthalate) is also blow-molded to make plastic soft-drink bottles that are sold by the billions each year. 

If you pick up an empty 2-liter plastic soft drink bottle and look at its underside, you will see molded in the plastic a set of arrows in a triangle arrangement with a I inside. What does the I mean ... 

Fill a plastic soft drink bottle with water, and replace the cap tightly. 

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. 

The mechanical compatibilisation of polymer blends is conceptually an attractive route, leading to unique property combinations and the recycling of mixed polymer scrap. There is considerable impetus behind discovering polymers that exhibit such compatibilising effects and to understand the mechanisms by which they function. Blends would result if certain types of plastic soft-drink bottles were granulated and processed. A bottle type of interest consists of a PET container with an HOPE pedestal, which is needed because the blown bottle has a rounded bottom. It is quite obvious that PET and any PO would be grossly incompatible and that a very effective compatibiliser would be needed to give the blend adequate mechanical properties for any subsequent application [76]. 

Last year, 100 million pounds of post-consumer plastic soft drink bottles were recycled in the U.S. — about 20 percent of all the PET in the bottle market. According to the Plastic Bottle Institute, by 1988, more than 230 million... 

Major component of plastic soft drink bottles. 

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.)... 

CI.43 The plastic known as PETE (polyethyleneterephthalate) is a polymer of terephthalic acid and ethylene glycol. PETE is used to make plastic soft drink bottles and containers for salad dressings, shampoos, and dishwashing liquids. Today, PETE is the most widely recycled of all the plastics in a single year, 2.4 X 10 lb of PETE are recycled. After PETE is separated fiom other plastics, it can be used in polyester fabric, fill for sleeping bags, door mats, and tennis ball containers. The density of PETE is 1.38 g/mL. (2.6, 2.7, 8.4,17.6)... 

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