PET - PLASTIC BOTTLES

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Nestle, Pepsi and Coke Face Their Waterloo

As the Backlash Against Plastic Bottles Hits Its Stride, Water Marketers Are Fighting to Protect Their $16 Billion Business  -  October 08, 2007 - NEW YORK  Adage.com

When Robert Rheaume met with retail buyers last year, his $20 Sigg aluminum water bottles were a tough sell. After all, the market was limited mainly to hikers and campers, many of whom were already devoted to Nalgene's $10 plastic version. But after this summer's deluge of headlines about the environmental impact of plastic water bottles, he's got more buyers than he even wants.

"Now the same people that were blowing me off a year ago are calling me and saying, 'OK, I get it. How can I get onboard?'" Mr. Rheaume said.

Sigg -- which has the added bonus of not being made in China -- has been approached by several mass-market retailers in recent months as the once-booming $16 billion bottled-water industry, dominated by industry giants such as Nestlé, Coke and Pepsi, comes under siege.

PET mineral water bottle waste mountain

Local level

City governments have taken up the bottled-water cause. San Francisco Mayor Gavin Newsom (who recently banned plastic grocery bags) has banned plastic water bottles in city offices and is encouraging city residents to drink from the tap. New York Mayor Michael Bloomberg has issued similar warnings.

Americans are taking heed. A Google search for "stop using plastic water bottles" turned up 2.3 million hits. "Bottled-water waste" turned up 1.9 million.

Sales are slowing as well. Beverage Digest reports that retail sales of bottled water (excluding vending machines and Wal-Mart) grew only 9% this year compared with 16% in 2006. Editor John Sicher doesn't think this has to do with the negative publicity and attributes it to the inevitable slowing of a long-booming industry. Not everyone agrees.

"This could be pretty significant," said Joe Pawlak, VP of restaurant consultant Technomic. "People are being more socially conscious, whether it's global warming, sustainability or landfills. I think it's an offshoot of the boomers wanting to leave a positive legacy."

PR campaign

According to water-filtration company Brita (owned by bleach giant Clorox), Americans discard 38 billion plastic water bottles a year, and it takes 1.5 billion barrels of oil to produce them.

Joe Doss, president of the International Bottled Water Association, said the bottled-water industry has been unfairly targeted. He claims that bottled water is America's No. 2 beverage (after soda) but accounts for only a third of 1% of the nation's waste. "We strongly think any efforts to reduce the environmental impact of packaging must focus on all consumer goods and not just target one industry, like bottled water," he said.

To present that point of view, in August the association began a PR and advertising campaign in newspapers such as The New York Times and San Francisco Chronicle to, as the association says, "bring balanced, positive and factual bottled-water information to consumers and community leaders."

Individual bottlers, meanwhile, are struggling to stem the tide of cold water. "I get the sense that there's a desire to vilify our industry and point to it as hurting the community," said an insider at a major bottler.

Light-weighting

Manufacturers are reducing the materials required for their bottles, which is known as light-weighting. In recent years, Coca-Cola has reduced its Dasani bottle weight 30%, to 16 grams. PepsiCo has reduced its Aquafina bottles nearly 40%, to 15 grams, and Nestlé Waters is introducing a 12.5 gram bottle this month. Its last model was 14.5 grams. Nestlé, which owns Deer Park, Ice Mountain and Polar Spring waters, among many others, has a lot at stake. It controls nearly $4 billion of the $5 billion grocery market for single-serving bottles, according to Information Resources Inc.

While the majors are rushing to make changes, reusable-bottle companies are working to make their brands better known. Nalgene is reaching out to the mass market for the first time. Brita -- which, of course, competes with the bottled-water industry -- approached Nalgene this summer for a co-branded campaign encouraging consumers to filter tap water at home. Participants pledge at FilterForGood.com to avoid plastic water bottles for a month, a week or a year. Nalgene is also selling a $10 "Refill Not Landfill" bottle and donating $4 to the Blue Planet Run Foundation.

"With all of the press and interest in bottled-water waste, we wanted to provide a solution," said Brita Brand Manager Hank Mercier. "Brita water plus Nalgene gives you great healthy water with the convenience of being able to carry it around as well." Mr. Mercier said Brita has experienced strong sales growth since the media blitz against plastic bottles began.

Personal change

At Nalgene, Senior Marketing Manager Eric Hansen said the response has been overwhelming. "This resonates with a lot of people because so many environmental issues are so big that people can't get their head around them," he said. "Global warming is a good example. How does someone make a change in their daily habits that lets them feel like they're making a difference?"

Mr. Hansen said his company is in talks with at least three mass-market retailers interested in carrying Nalgene products in their stores. Nalgene Outdoor is the cool offshoot catering to outdoorsmen of Nalgene Nunc Corp., which primarily makes packaging, lab and scientific equipment. But even Nalgene isn't immune from controversy: The marketer has been battling some public perceptions that its thick-plastic bottles have been known to leach on the first few uses, giving a plastic taste to the water, and that they retain the flavor of other beverages -- sometimes for the life of the bottle.

"It's been an issue for us," Mr. Hansen said. The company's official statement on the leaching issue -- posted on the Nalgene Outdoor website, says: "Based on the findings of the Food and Drug Administration, the Environmental Protection Agency, The American Plastics Council and other reliable sources from around the world, we continue to firmly believe in the safety of our products."

PET Lilt bottle

Bottle-to-bottle

Nestlé spokeswoman Jane Lazgin said her company has been working on bottles made from renewable material for several years. Just getting the plastic bottles to 12.5 grams meant re-engineering the bottle so it could stand up, avoid leaks and sustain suction.

Earlier this month, Coca-Cola pledged $60 million to build recycling plants. One of the plants, in Spartansburg, S.C., will be the world's largest bottle-to-bottle recycling plant -- meaning new bottles are made directly from old ones. A big problem, said Coke spokeswoman Diana Garza, is that many consumers don't have curbside recycling. Neither Coke nor Pepsi is working on a nonplastic bottle at present. They'll need to.

Even so, Technomic's Mr. Pawlack said manufacturers' recent moves are just "Band-Aids."

"They're going to be looking into more environmentally friendly packing that's biodegradable, easier to recycle or made from totally different materials," he said. "They're going to be looking at all of these types of things as we move forward. We think this whole social-consciousness issue is here to stay."

Emily Bryson York

POLYETHLENE TEREPHTHALATE

Polyethylene terephthalate (aka PET, PETE or the obsolete PETP or PET-P) is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber. It is one of the most important raw materials used in man-made fibers.

Depending on its processing and thermal history, it may exist both as an amorphous (transparent) and as a semi-crystalline (opaque and white) material. Its monomer can be synthesized by the esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct, or the transesterification reaction between ethylene glycol and dimethyl terephthalate with methanol as a byproduct. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with ethylene glycol as the byproduct (the ethylene glycol is recycled in production).

The majority of the world's PET production is for synthetic fibers (in excess of 60%) with bottle production accounting for around 30% of global demand. In discussing textile applications, PET is generally referred to as simply "polyester" while "PET" is used most often to refer to packaging applications.

It is manufactured under trade names Arnite, Impet and Rynite, Ertalyte, Hostaphan, Melinex and Mylar films, and Dacron, Diolen, Terylene & Trevira fibers. 

PET boat sails

Uses

A PET soft drink bottlePET can be semi-rigid to rigid, depending on its thickness, and is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier to alcohol (requires additional "Barrier" treatment) and solvents. It is strong and impact-resistant. It is naturally colorless and transparent.

When produced as a thin film (often known by the tradename Mylar), PET is often coated with aluminium to reduce its permeability, and to make it reflective and opaque. PET bottles are excellent barrier materials and are widely used for soft drinks, (see carbonation). PET or Dacron is also used as a thermal insulation layer on the outside of the International Space Station as seen in an episode of Modern Marvels "Sub Zero". For certain specialty bottles, PET sandwiches an additional polyvinyl alcohol to further reduce its oxygen permeability.

When filled with glass particles or fibers, it becomes significantly stiffer and more durable. This glass-filled plastic, in a semi-crystalline formulation, is sold under the tradename Rynite, Arnite, Hostadur& Crastin.

Sails are usually made of Dacron, a brand of PET fiber; colorful lightweight spinnakers are usually made of nylon.While all thermoplastics are technically recyclable, PET bottle recycling is more practical than many other plastic applications. The primary reason is that plastic carbonated soft drink bottles and water bottles are almost exclusively PET which makes them more easily identifiable in a recycle stream. PET has a resin identification code of 1. PET, as with many plastics, is also an excellent candidate for thermal recycling (incineration) as it is composed of carbon, hydrogen and oxygen with only trace amounts of catalyst elements (no sulfur) and has the energy content of soft coal.

One use for recycled PET bottle is for the manufacture of polar fleece material.

PET was patented in 1941 by the Calico Printers' Association of Manchester. The PET bottle was patented in 1973.

Intrinsic viscosity

One of the most important characteristics of PET is referred to as I.V.(intrinsic viscosity).

The I.V. of the material, measured in dl/g (deciliters/gram) is dependent upon the length of its polymer chains. The longer the chains, the stiffer the material, and therefore the higher the I.V. The average chain length of a particular batch of resin can be controlled during polymerization.

An I.V. of about:

0.60 - Would be appropriate for fiber 
0.65 - Film 
0.76-0.84 - Bottles 
0.85 - Tire cord 

Drying

PET is hygroscopic, meaning that it naturally absorbs water from its surroundings. However, when this 'damp' PET is then heated a chemical reaction known as hydrolysis takes place between the water and the PET which reduces its molecular weight (IV) and its physical properties. This means that before the resin can be processed in a molding machine, as much moisture as possible must be removed from the resin. This is achieved through the use of a desiccant or dryers before the PET is fed into the processing equipment.

Inside the dryer, hot dry air is pumped into the bottom of the hopper containing the resin so that it flows up through the pellets removing moisture on its way. The hot wet air leaves the top of the hopper and is first run through an after-cooler, because it is easier to remove moisture from cold air than hot air. The resulting cool wet air is then passed through a desiccant bed. Finally the cool dry air leaving the desiccant bed is re-heated in a process heater and sent back through the same processes in a closed loop. Typically residual moisture levels in the resin must be less than 40 ppm before processing. Dryer residence time should not be shorter than about four hours. This is because drying the material in less than 4 hours would require a temperature above 160 °C, at which level hydrolysis would begin inside the pellets before they could be dried out.

Copolymers

In addition to pure (homopolymer) PET, PET modified by copolymerization is also available.

In some cases, the modified properties of copolymer are more desirable for a particular application. For example, cyclohexane dimethanol (CHDM) can be added to the polymer backbone in place of ethylene glycol. Since this building block is much larger (6 additional carbon atoms) than the ethylene glycol unit it replaces, it does not fit in with the neighboring chains the way an ethylene glycol unit would. This interferes with crystallization and lowers the polymer's melting temperature. Such PET is generally known as PETG (EastmanChemical and SKchemicals are the only two manufacturers).

Replacing terephthalic acid (right) with isophthalic acid (center) creates a kink in the PET chain, interfering with crystallization and lowering the polymer's melting point.Another common modifier is isophthalic acid, replacing some of the 1,4- (para-) linked terephthalate units. The 1,2- (ortho-) or 1,3- (meta-) linkage produces an angle in the chain, which also disturbs crystallinity.

Such copolymers are advantageous for certain molding applications, such as thermoforming, which is used to make tray or blister packages from PET sheet (sometimes called APET, for "amorphous PET"). On the other hand, crystallization is important in other applications where mechanical and dimensional stability are important, such as seat belts. For PET bottles, the use of small amounts of CHDM or other comonomers can be useful: if only small amounts of comonomers are used, crystallization is slowed but not prevented entirely. As a result, bottles are obtainable via stretch blow molding ("SBM"), which are both clear and crystalline enough to be an adequate barrier to aromas and even gasses, such as the carbon dioxide in carbonated beverages.

Crystals

Crystallization occurs when polymer chains fold up on themselves in a repeating, symmetrical pattern. Long polymer chains tend to become entangled on themselves, which prevents full crystallization in all but the most carefully controlled circumstances. PET is no exception to this rule; 60% crystallization is the upper limit for commercial products, with the exception of polyester fibers.

PET in its natural state is a crystalline resin. Clear products can be produced by rapidly cooling molten polymer to form an amorphous solid. Like glass, amorphous PET forms when its molecules are not given enough time to arrange themselves in an orderly fashion as the melt is cooled. At room temperature the molecules are frozen in place, but if enough heat energy is put back into them, they begin to move again, allowing crystals to nucleate and grow. This procedure is known as solid-state crystallization.

Like most materials, PET tends to produce many small crystallites when crystallized from an amorphous solid, rather than forming one large single crystal. Light tends to scatter as it crosses the boundaries between crystallites and the amorphous regions between them. This scattering means that crystalline PET is opaque and white in most cases. Fiber drawing is among the few industrial processes that produces a nearly single-crystal product.


Degradation

PET is subject to various types of degradations during processing. The main degradations that can occur are hydrolytic, thermal and probably most important thermal oxidation. When PET degrades, several things happen: discoloration, chain scissions resulting in reduced molecular weight, formation of acetaldehyde and cross-links ("gel" or "fish-eye" formation). Discoloration is due to the formation of various cromophoric systems following prolonged thermal treatment at elevated temperatures. This becomes a problem when the optical requirements of the polymer are very high eg in packaging applications. Acetaldehyde is normally a colorless gas with a fruity smell. It forms naturally in fruit, but it can cause an off-taste in bottled water. Acetaldehyde forms in PET through the "abuse" of the material. High temperatures (PET decomposes above 300 °C or 572 °F), high pressures, extruder speeds (excessive shear flow raises temperature) and long barrel residence times all contribute to the production of acetaldehyde. When acetaldehyde is produced, some of it remains dissolved in the walls of a container and then diffuses into the product stored inside, altering the taste and aroma. This is not such a problem for non-consumables such as shampoo, for fruit juices, which already contain acetaldehyde or for strong-tasting drinks, such as soft drinks. For bottled water, low acetaldehyde content is quite important, because if nothing masks the aroma, even extremely low concentrations (10-20 ppb) of acetaldehyde can produce an off-taste. The thermal and thermooxidative degradation results in poor procesibility characteristics and performance of the material.

One way to alleviate this is to use a copolymer. Comonomers such as CHDM or isophthalic acid lower the melting temperature and reduces the degree of crystallinity of PET (especially important when the material is used for bottle manufacturing). Thus the resin can be plastically formed at lower temperatures and/or with lower force. This helps to prevent degradation, reducing the acetaldehyde content of the finished product to an acceptable (that is, unnoticeable) level. See copolymers, above. Other ways to improve the stability of the polymer is by using stabilizers, mainly antioxidants such as phosphites. Recently, molecular level stabilization of the material using nanostructured chemicals has also been considered.


Antimony

Antimony trioxide (Sb2O3) is a catalyst that is often used in the production of PET. It remains in the material and can thus in principle migrate out into food and drinks. Although antimony trioxide is of low toxicity, its presence is still of concern. The Swiss Federal Office of Public Health investigated the amount of antimony migration, comparing waters bottled in PET and glass: the antimony concentrations of the water in PET bottles was higher, but still well below the allowed maximal concentrations.[1] (report available in German and French only) The Swiss Federal Office of Public Health concluded that the health risk of these low concentrations is negligible (1% of the "tolerable daily intake" determined by the WHO).

Re-crystallization

PETE has SPI resin ID code 1 
Recrystallized PETPET can be used to explore the crystallization of amorphous solids. The resin identification code can be used to verify the type of plastic it is made of: many plastic beverage bottles have the letters PET or PETE and a code of 1 on the bottom, near the center. When a flame is held several inches below the bottle and slowly brought closer, part of the material will visibly change. This happens because high temperatures melt the PET. This releases the tension that was frozen in during the blow molding process and the polymer chains will shift to a more relaxed and disordered state, which results in shrinkage of the softened area. Because of the decreased order of the polymer chains, there are now fewer crystal nuclei. Consequently, when the crystallites re-form upon cooling they grow larger than the original crystallites in the bottle wall. Because the new crystallites are larger than the wave length of light, they will now cause light to scatter, giving the material an opaque white appearance.


Processing Equipment

There are two basic molding methods, one-step and two-step. In two-step molding, two separate machines are used. The first machine injection molds the preform. The preform looks like a test tube. The bottle-cap threads are already molded into place, and the body of the tube is significantly thicker, as it will be inflated into its final shape in the second step using stretch-blow molding.

In the second process, the preforms are heated rapidly and then inflated against a two-part mold to form them into the final shape of the bottle. Preforms (uninflated bottles) are now also used as containers for candy.

In one-step machines, the entire process from raw material to finished container is conducted within one machine, making it especially suitable for molding non-standard shapes (custom molding), including jars, flat oval, flask shapes etc. Its greatest merit is the reduction in space, product handling and energy, and far higher visual quality than can be achieved by the two-step system.

LINKS and REFERENCE

• American Plastics Council info on plastic bottles, refilling, PET safety

• Publications about PET and PET bottles

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