Polyethylene terephthalate

Polyethylene terephthalate, or PET, is a thermoplastic polymer resin. PET is created by combining chemicals ethylene glycol and purified terephthalic acid. PET is a remarkably versatile product. It is the most commonly used product in packaging beverages and food. It is identifiable by the number 1 code appearing at or near the bottom of the container. PET packaging is nearly 100 percent recyclable. It has the strength and safety of glass and the durability of metal. PET does not leach toxins or chemicals, making it safe for food and medicine. It is transparent, so consumers can see what is inside the containers and the condition of the products. PET is lightweight, yet strong enough to stack products one atop the other; it can be resealed and is shatter-resistant. Strength and durability make PET fibers ideal in making clothes, carpets, sleeping bags, winter coats, auto parts, and dog beds.

Background

Scientist W.H. Carothers was searching for synthetic polyester fibers to use in making textile products. Instead, Carothers discovered nylon, distracting him from the search for polyester fibers. British scientists Whinfield and Dickson later followed up Carothers’s research. Their work led to discovering polyester fibers for making fabrics, plastic sheets, and films. They trademarked the name Mylar for commercial use in 1951. PET began appearing under other brand names over the years, including Dacron and Terylene for polyester fibers in textiles. Later in the 1950s, researchers developed methods for stretching PET into thin sheets like a film. PET’s properties were found to be ideal in making video, photo, and X-ray film; magnetic recording tape; and packaging films of varying thickness.

The first PET bottles began appearing in 1973; they were transparent, lightweight, held their shape, and were shatterproof. By 1977, local governments, overwhelmed with the plethora of plastic bottles littering and in dumpsters, worked with retailers to begin recycling PET bottles. Containers made from PET resins are universally used for soft drinks and water.

The discoveries birthed the polyester and textile industries that grew rapidly. Polyester fibers were inexpensive to produce and tough. Polyester fibers were an ideal alternative to expensive, handmade cotton (pick, spin, and weave), wool, and silk materials and processes for making clothes. The inventions eventually led to the mass-market, affordable clothing industry that became a staple of big-box discount stores. Polyester morphed into luxury microfibers and blends ("pressing" polyester fibers with rayon, wool, or cotton) that became the basis for wrinkle-resistant, wash-and-wear, no-iron clothes. By the 1980s, the public was unable to distinguish between polyester and natural fiber clothes made from cotton, wool, and silk.

Monsanto and two MIT architects built a plastic house in 1957 at Disneyland’s "Tomorrowland," which showcased products for the future. Everything inside and out was made from plastic including walls, floors, doors, handles and knobs, dishes, drapes, bathtubs, and much more.

Polyethylene Terephthalate Today

All the clothes in the closets of the Monsanto plastic house were made from synthetic fibers. What polyester did for textiles, plastic did replace raw materials, including wood, metals, ivory, rubber, and shellac. Plastic is inexpensive and molded easily to manufacturers’ needs. What Monsanto envisioned as the future—1987—became the reality in advanced societies. The ubiquitous PET products invigorated the garbage and recycling industries but shattered companies cleaning and refilling glass bottles; laundering baby diapers disappeared with the advent of disposable diapers; the list of societal changes and industry restructuring is staggering.

The wondrous uses of PET-based products inspired research and development of other plastic products like PVC used for plumbing in modern home construction. None of this progress has been without health concerns. Xylene, vinyl chloride, and benzene are cancer-causing chemicals commonly used in the manufacture of plastics. Governments in some communities ban PVC for potable water (not for sewage), because PVC releases carcinogens, heavy metals, and mercury. Acetaldehyde leaches from PET bottles for water and sodas, while other plastics are used for milk bottles, yogurt cups, and plastic bags. The numbering system mentioned earlier extends from one to seven, so higher numbers are less safe and banned in some areas.

In addition to recycling, scientists are experimenting with bacterial biological agents to biodegrade and eliminate PET products. In 2016, the weight of PET-produced products reached fifty-six million tons, making it the workhorse material of the modern economy. In addition to health concerns, plastic pollution is a concern; a third of PET products are never recycled but are dumped—harming the oceans and land use and clogging urban infrastructures.

Greenhouse gas emissions in the production of plastics are a $40b problem. An international movement to deal with the problems, called The New Plastics Economy, detailed in a report by the World Economic Forum—demonstrated the global concerns about PET and six other types of plastics:

Polyethylene terephthalate is the most widely used for water, soda, cooking oil, peanut butter, and other containers; it is not recommended for reuse or refilling. High Density Polyethylene (HDPE) is used for milk containers, detergents, yogurt, bottle caps, hard hats, and other types of containers. It is a non-translucent plastic that is dishwasher safer, but discolors. Polyvinyl chloride (PVC) is used to make plastic pipes, Saran wrap, furniture, flooring, and other plastic products. PVC is a human carcinogen, and acute exposure causes illnesses. Low-density polyethylene (LDPE) makes plastic film, grocery bags, and trashcan liners. LDPE does not break down without leaching carcinogens. Polypropylene (PP) is used in straws and food containers because of its durability. Packaging pellets, Styrofoam peanuts, and plastic spoons and forks are made from Polystyrene (PS). It causes a terrible litter problem, marine debris, and hurts wildlife, among other environmental damage. A newer plastic, Eastman Tritan, is resistant to chemicals and does not degrade as other plastic materials do. It has the look of glass, but is lightweight and shatterproof. The next generation of plastics research is addressing the demand for sustainable criteria.

Bibliography

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"What Is PET?" American Beverage, 9 Feb. 2024, www.americanbeverage.org/education-resources/blog/what-is-pet/. Accessed 20 Nov. 2024.

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