PET Bottles

PET is composed by ethylene and paraxylene.  Their derivatives, respectively named ethylene glycol and terephthalic acid, react at high temperature pressure.  The result is amorphous PET.  The resin is then crystallised and polymerised to increase its molecular weight and its viscosity. The resulting resin is the raw material used to make containers.     A recent addition is renewable bio-PET sourced from sugar cane.  This renewable source lessens the dependency on fossil fuels for plastic bottle manufacturer.  PCR (post consumer resin) is also a environmentally friendly resin, as it is made from recycled HDPE bottles and PET plastic bottles.  Bottle neck finishes range from as small as 18mm to 120mm wide mouth.  The applications for plastic PET bottles continue to expand.  From water to automotive products, from honey to liquor, PET plastic bottles are the packaging solution of choice. Plastic PET bottles provide the look of glass with improved functionality:

  • resistant to breakage
  • better product dispensing
  • reduced weight 
  • lowering your shipping costs &
  • reducing your warehousing expenses
  • lower corrugation costs
  • decibel reduction

Your choice of plastic PET bottles versus other plastic containers might hinge on:

  • Clarity
  • Impact resistance
  • Recyclability

PET is used to make many products, such as polyester fabric, cable wraps, films, transformer insulation, generator parts, and packaging. It makes up 6.4 % of all packaging and 14 % of all plastic containers, including the popular soft drink bottle. Accounting for 43 % of those sold, PET is the most widely used soft drink container.   The PET bottles adopted for beverages, following their applications are categorized as:

  • PET Bottle.     The raw material of PET is a heat plasticity resin that is called Polyethylene Terephthalate, a type of polyester. By using PET resin, a biaxial blow stretching mold is used to form the bottle, which is generally used for beverage container applications.
  • Aseptic PET Bottle.   A PET bottle used for aseptic filling, a process of packaging “sterile liquid” in a “sterilized PET bottle” at room temperature in an aseptic environment.
  • Hotfill PET Bottle.   A heat resistant PET bottle for hot-fill application. Beverages are sterilized and filled at a high temperature and then cooled in a shower of cold water.
  • Pressure Resistant PET Bottle (CSD Beverages).  A PET bottle for carbonated beverages which is designed to withstand internal pressure of carbonated gas in the bottle.
  • Pressure-Heat Resistant Bottle.  A PET bottle for carbonated beverages requiring heat sterilization.   Equipped with both heat and pressure resistance.
  • Large Capacity Alcohol PET Bottle.  A large capacity PET bottle developed for alcohol use. Available in economic 2.7 L bottle size with ergonomic design, and a 4 L bottle with an easy-to-use handle.

Aluminum, a close second, is 34 %, while glass, which used to be 100 % of the bottles, is only a small percentage of those sold today. Plastics were first made in the 1800s from natural substances that were characterized by having chains of molecules. When these substances were combined with other chemicals in the laboratory, they formed products of a plastic nature. While hailed as a revolutionary invention, early plastics had their share of problems, such as flammability and brittleness. Polyesters, the group of plastics to which PET belongs, were first developed in 1833, but these were mostly used in liquid varnishes, a far cry from the solid, versatile form they took later.  Purely synthetic plastics that were a vast improvement on earlier plastics arrived in the early 1900s, yet they still had limited applications.  Experimentation continued, with most of the hundreds of new plastics created over the next several decades failing commercially. PET was developed in 1941, but it wasn't until the early 1970s that the plastic soda bottle became a reality.  Nathaniel C. Wyeth, son of well-known painter N. C. Wyeth and an engineer for the Du Pont Corp., finally developed a usable bottle after much experimentation.  Wyeth's crucial discovery was a way to improve the blow-molding technique of making plastic bottles. Blow molding is ancient, having been used in glass-making technology for approximately two thousand years. Making plastic bottles by blow molding didn't happen until suitable plastics were developed around 1940, but production of these bottles was limited because of inconsistent wall thickness, irregular bottle necks, and difficulty in trimming the finished product. Wyeth's invention of stretch blow molding in 1973 solved these problems, yielding a strong, lightweight, flexible bottle. The overwhelming success of PET soda bottles has resulted in a disposal problem, but recycling of the bottles is growing, and manufacturers are finding new ways to use recycled PET.

Raw Materials

PET is a polymer, a substance consisting of a chain of repeating organic molecules with great molecular weight. Like most plastics, PET is ultimately derived from petroleum hydrocarbons. It is created by a reaction between terephthalic acid and ethylene glycol.  Terephthalic acid is an acid formed by the oxidation of paraxylene, an aromatic hydrocarbon, using just air or nitric acid. Paraxylene is derived from coal tar and petroleum using fractional distillation, a process that utilizes the different boiling points of compounds to cause them to "fall out" at different points of the process.  In plastic soda bottle manufacture, the polyethylene terephthalate (PET) plastic is processed following tghe sequence: 

  1. polymerization, involving creation of long strings of molecules;
  2. stretch blow molding. In this process, a long tube (parison) of PET is put into a mold, and a steel rod (mandrel) is inserted into it;
  3. highly pressurized air shoots through the mandrel and forces the parison against the walls of the mold;
  4. a separate bottom piece is inserted into the mold to shape the bottle so that it can stand on a flat surface.  Ethylene glycol is derived from ethylene indirectly through ethylene oxide, a substance also found in antifreeze. Ethylene is a gaseous hydrocarbon that is present in petroleum and natural gas, but is usually derived industrially by heating ethane or an ethane-propane mixture.

The Manufacturing Process


Before the bottles can be made, the PET itself must be manufactured, or polymerized. In polymerization, smaller molecules are combined to form larger substances. To make PET, terephthalic acid is first combined with methanol. This reaction yields dimethyl terephthalate and water. Next, the dimethyl terephthalat, is combined with an excess of ethylene glycol at 150 ºC to yield another substance, bis 2-hydroxyethyl terephthalate and methanol.

The final step of polymerization involves the condensation polymerization of the bis 2-hydroxyethyl terephthalate. In this process, a polymer is formed while another molecule is released, or "falls out." The condensation polymerization of bis 2-hydroxyethyl terephthalate is carried out in a vacuum at 530 degrees Fahrenheit (275 degrees Celsius) and results in chains of PET and ethylene glycol (see step #1 above); the latter substance is continuously removed during polymerization and used to make more PET. After the PET mixture reaches the required viscosity (thickness), it is cooled to avoid degradation and discoloration. Later, it can be reheated for its various uses.


PET beverage bottles are made using a process known as stretch blow molding (also called orientation blow molding). First, PET pellets are injection molded—heated and put into a mold—into a thin walled tube of plastic, called a parison. The parison is then cooled and cut to the proper length.

Next, the parison tube is re-heated and placed into another mold, which is shaped like a soda bottle, complete with screwtop. A steel rod (a mandrel) is slid into the parison. Highly pressurized air then shoots through the mandrel and fills the parison, pressing it against the inside walls of the mold. The pressure of the air stretches the plastic both radially ("out") and axially ("down"). The combination of high temperature and stretching in the desired direction causes the molecules to polarize, line up and essentially crystallize to produce a bottle of superior strength. The entire procedure must be done quickly, and the plastic must be pressed firmly against the wall, or the bottle will come out misshapen. In order to give the bottom of the bottle its proper concave shape (so that it can stand upright) a separate bottom piece is attached to the mold during the blowing process.

The mold must then be cooled. Different cooling methods are used. Water in pipes may flow around the mold, or liquid carbon dioxide, highly pressurized moist air, or room air is shot into the bottle to cool it more directly. The procedure is preferably done quickly, to set the bottle before creep (flow) occurs.

The bottle is then removed from the mold. In mass production, small bottles are formed continuously in a string of attached bottles that are separated and trimmed. Other trimming must be done wherever the plastic leaked through the cracks of the mold (like the way pancake batter does when squeezed in a waffle maker). Ten to 25 % of the plastic is lost this way, but it can be reused.

Some soft drink producers make their own bottles, but usually finished bottles are sent from specialty manufacturers to soft drink companies in trucks. Plastic is cheap to transport because it is light. Accessories such as lids and labels are manufactured separately. Occasionally, the plastic bottle manufacturer will put labels supplied by the soft drink company on the bottles before shipping them.

Quality Control

Polymerization is a delicate reaction that is difficult to regulate once the conditions are set and the process is set into motion. All molecules produced during the reaction, some of which might be side effects and impurities, remain in the finished product. Once the reaction gets going, it's impossible to stop it at mid-point and remove impurities, and it is also difficult and expensive to eliminate unwanted products when the reaction is complete. Purifying polymers is an expensive process, and quality is hard to determine. Variations in the polymerization process could make changes that are undetectable in routine control tests.  The polymerization of terephthalic acid and ethylene glycol can yield two impurities: diethylene glycol and acetaldehyde. The amount of diethylene glycol is kept to a minimum, so that PET's final properties are not affected. Acetaldehyde, which is formed during the polymerization as well as during the production of the bottle, will give a funny taste to the soft drink if it occurs in large enough amounts. By using optimum injection-molding techniques that expose the polymer to heat for a short time, very low concentrations of acetaldehyde appear and the taste of the beverage will be unaffected.  Testing is performed on those specific characteristics of PET that make it perfect for beverage bottles. Numerous standards and tests have been developed for plastics over the years. For instance, PET must be shatter-proof under normal conditions, so bottles undergo impact resistance tests that involve dropping them from a specific height and hitting them with a specified force. Also, the bottle must hold its shape as well as resist pressure while stacked, so resistance to creep is measured by testing for deformity under pressure. In addition, soft drinks contain carbon dioxide; that's what gives them their fizz. If carbon dioxide were able to escape through the bottle's plastic walls, most beverages bought would have already gone flat. Hence, the bottle's permeability to carbon dioxide is tested. Even its transparency and gloss are tested. All tests aim for consistency of size, shape, and other factors.

PEF Bottles

PEF (polyethylene-furanoate), is a 100% biobased and recyclable polymer that can be applied to an enormous range of applications.   

PEF could replace PET in typical applications like films, fibers and in particular bottles for the packaging of soft drinks, water, alcoholic beverages, fruit juices food and non-food products.  PEF’s barrier and thermal properties are superior to conventional PET.      

In combination with a significantly reduced carbon footprint, the added functionality, gives PEF all the attributes to become the next generation polyester. In the near future PEF is positioned to become the material of choice for beverage bottles and other polyester applications.

Recyclable and Renewable

PEF is made from plant-based sugars, which means it is renewable: PEF doesn’t rely on carbon derived from fossil feedstock but is made from plants that convert CO2 from the atmosphere into carbohydrates by using solar energy (photosynthesis).

Avantium is closely collaborating with the recycling community to find the optimum end-of-life solutions for PEF. Technical data demonstrates PEF to PEF recycling will be feasible. During a transition period PEF will be mixed in the recycled PET stream. Experiments to determine the compatibility of PEF with PET recycling show PEF has no impact on mechanical and physical properties of PET.  

Polyester polyethylene-furanoate (PEF), which is an analogue of polyethylene-terephthalate (PET).  PEF could replace PET in typical applications like films, fibers and in particular bottles for the packaging of soft drinks, water, alcoholic beverages, fruit juices food and non-food products.

A Renewable Packaging Footprint

Avantium has entered into joint development agreements with The Coca-Cola Company (TCCC), Danone and ALPLA to further develop and commercialize PEF bottles. These three companies have a proven leadership position in the area of sustainability and the use of renewable packaging materials. By light-weighting their PET bottles, a strong reduction of the carbon footprint of their supply chains can be obtained (in the last eight years the average weight of a 16-ounce PET bottle has been reduced by 30%). Today, TCCC and Danone are industry leaders in adopting plant based materials for their beverage packaging. TCCC introduced the partially bio-based bottle back in November 2009 under the brand name PlantBottle™ for its Coca-Cola™ and Dasani™ brands, replacing fossil based MEG by plant based MEG. Also applying plant based MEG, Danone introduced a partially plant based bottle for its Volvic water brand in 2010, called Greener Bottle, or Bouteille Végétale. ALPLA is a leading company in PET conversion, making PET bottle packaging for leading brand owners like Unilever, P&G and the Coca-Cola Company. ALPLA has applied biobased MEG in its PET packaging, and will now introduce PEF to customers in the food, home care/personal care and alcoholic beverages industry.

Superior Functional Properties

PEF bottles outperform PET bottles in many areas, particularly barrier properties (the ability of the polymer to withstand gas permeability through the bottle). PEF’s ability to seal out oxygen, for example, results in longer-lasting carbonated drinks and extended shelf life. Moreover, PEF makes certain packaging coatings redundant, like the coatings used on bottles to keep beer fresh. In terms of thermal properties, PEF is widely considered more attractive than PET due to its superior ability to withstand heat (expressed in the glass transition temperature or Tg) and process-ability at lower temperatures (expressed in the melting temperature or Tm).

Superior barrier properties:

  • PEF oxygen barrier is 10 times better than PET
  • PEF carbon dioxide barrier is 4 times better than PET
  • PEF water barrier is 2 times better than PET

More attractive thermal properties:

  • The Tg of PEF is 86°C compared to the Tg of PET of 74°C
  • The Tm of PEF is 235°C compared to the Tm of PET of 265°C

Recycling PEF bottles:

It has demonstrated that PEF can be recycled in very similar ways to PET recycling.

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