Du Pont researchers invented the polyethylene-terephthalate (PET) bottle, which was made of a plastic that could be conveniently recycled and soon became one of the most common consumer plastics.
Called by inventor Nathaniel Wyeth “the epitome of an invention,” the plastic soda bottle replaced glass bottles as the standard method of containing soft drinks in the 1970’s. Carbonated drink manufacturers had used glass bottles and aluminum cans to contain their beverages, long believing that pressure exerted by carbonated drinks would cause plastic containers to rupture. Wyeth was not convinced that was so, and he experimented with a detergent bottle filled with ginger ale. At first he sought to ameliorate the effects of the carbonation by keeping the product refrigerated, but when his first experiment resulted in the detergent bottle’s swelling, he realized that standard plastic bottles were indeed too weak to hold carbonated drinks.
The trick, he concluded, was to get the molecules of the plastic to “line up,” much the way a group of people in a tug-of-war pull in the same direction. Basing his work on experiments with nylon done at Du Pont by Wallace Hume Carothers
After the process was conceptualized, developing it went slowly, and at first Wyeth’s team made only eight bottles a day. It took one hour to set up the machinery to blow each bottle, then the team heated the plastic to 100 degrees Celsius and blew it into a mold. Nevertheless, based on that imperfect and primitive beginning, companies within a few years were turning out ten thousand bottles an hour.
In addition to other early problems, the first plastic Wyeth used was polypropylene;
With soft drinks making up a major portion of all beverages consumed annually, packaging constituted a significant portion of corporate and social resources. Originally, drink manufacturers such as the makers of Coca-Cola and Pepsi Cola preferred glass containers because people could see the beverage through the bottle. The Coca-Cola Company
Changing consumer tastes led Coke to switch to larger bottles made of plastics and to improve the resistance of those bottles. Before Wyeth developed the PET bottle, the industry had to rely on glass products such as the 1973 Surlyn-coated glass bottle, which had reduced overall weight along with increased toughness.
Over the years, the number of PET bottles increased singificantly while the number of glass bottles fell considerably. The earliest demand for plastic bottles stemmed from the preference for lighter bottles than those made of glass, which were heavy and breakable. Plastic gradually gained on glass and aluminum. Most of the PET bottles were quart size or larger.
Workers shovel plastic bottles into a shredder in a plastics recycling plant. Recycling is one means of reducing the impact of plastic on the environment.
A significant drawback to the use of PET in even greater numbers remained the inherent weakness of smaller plastic bottles: The more volume that was contained in a carbonated drink bottle, the longer the drink maintained its effervescence, regardless of the integrity of the seal. Unopened, a thirty-two-ounce carbonated drink in a PET bottle started to lose effervescence in approximately ten weeks; after exposure to air, the effervescence disappeared rapidly. Thus smaller containers, which were more popular, were not practical for plastic. By the end of the twentieth century, many soft drink manufacturers had started offering twenty-ounce drinks in PET bottles; these single-serving plastic bottles became the fastest-growing soft drink product.
The only significant competition for PET bottles came from Surlyn-coated bottles that could contain up to sixty-four ounces and still maintain structural integrity when dropped from as much as four feet. The use of PET bottles spread to other products, however, including salad dressing, vegetable oils, and peanut butter. The bottles could also be heated in microwave ovens, which gave them a flexibility not found in aluminum cans. The clear view of the contents was an added advantage over metal containers.
PET bottles appeared at a time when environmentalists had started to emphasize recycling
Coke and Pepsi developed different methods to depolymerize the PET bottle and raced for approval from the U.S. Food and Drug Administration (FDA) for their processes. The processes involved breaking the plastic down into its building blocks, purifying them, and then repolymerizing the components. The soda companies were not obligated to obtain FDA approval, but they knew that the first company to claim having developed a safe, recyclable bottle would enjoy a major public relations boost. Eventually, Wellman, which began recycling the bottles in 1981, emerged as the leading manufacturer and source of recycling for the PET bottles. The company manufactured three hundred million bottles annually from the 120 to 140 million pounds of PET bottles it had purchased for recycling.
Ironically, disposable plastic bottles created a problem for the recycling effort. To receive a government definition of “recyclable,” not only must a product be technically capable of being recycled but also the company must have a viable infrastructure in place, including facilities and transportation networks, for the recycling. (The U.S. government established the policy framework for managing the disposal of hazardous waste and municipal solid waste, or garbage, in 1976 with the Resource Conservation and Recovery Act.)
Many of the concerns about glass and aluminum bottles involved their presence in landfills.
Other issues related to landfill use appeared, however. Recycling waste such as paper involved the expenditures of energy, including the use of gas-burning trucks to pick up paper waste to process the recycled paper. Where landfill use was concerned, plastics represented only a small portion of the waste-disposal problem. Even so, plastic bottle recycling rates continued to lag behind other industries’ recycling rates.
Several studies by economists showed that recycling had many hidden costs, not the least of which was time. Losses in time related to sorting, packaging, and labeling waste products needed to be accurately measured. Recycling plastics required both heat and chemicals, both of which involved environmental tradeoffs. Glass, the most easily recycled product because it was composed essentially of sand and lime, required high levels of heat to process for reuse. Consequently, it took dramatic improvements in recycling processes to make them profitable. In the case of PET bottles, a market for the recycled material was needed, which ultimately did develop.
Once the profit motive appeared, the market for recycling increased rapidly. By the end of the twentieth century, plastics were reprocessed into fibers that could be made into clothing, rugs, and stuffing for such items as ski jackets. The leading recycling company, Wellman, supplied polyester carpet fibers, fiber for furniture cushions, and most of the black polyester for the lining of automobile trunks, among other products. The likelihood for even further recycling of PET bottles was thought to be great. What started out as a search for a lighter bottle resulted in recycling processes for an entire range of plastics.
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Azapagic, Adisa, Alan Emsley, and Ian Hamerton, eds. Polymers: The Environment and Sustainable Development. Hoboken, N.J.: John Wiley & Sons, 2003. A timely discussion on the impact of recycled polymers on the environment. Each chapter contains relevant sample questions and answers. -
Brown, Kenneth A. Inventors at Work: Interviews with Sixteen Notable American Inventors. Redmond, Wash.: Tempest Books, 1988. Contains a chapter on Wyeth and extensive discussions of the process by which he invented the PET bottle. Also useful as a case study of other inventors. -
Hounshell, David A., and John Kenly Smith, Jr. Science and Corporate Strategy: Du Pont R&D, 1902-1980. New York: Cambridge University Press, 1988. A thorough history of Du Pont and the corporation’s development of several polymers. -
Rathje, William, and Cullen Murphy. Rubbish: The Archaeology of Garbage. 1992. Reprint. Tucson: University of Arizona Press, 2001. Anthropologists look at several landfills across the United States and discuss what they contain. Useful background. -
“Recycled PET Bottle Wins FDA Approval.” Beverage Industry, February, 1991, 22. A short discussion of Coke’s and Pepsi’s attempts to gain FDA approval of their PET recycling process.
Oregon Bans Nonrefillable Bottles