Delve into the science behind PET, examining its chemical composition and physical properties that make it such a durable plastic. We also discuss the various applications of PET, its environmental impact, and how advancements in PET recycling are helping to make it a more sustainable material.
Polyethylene terephthalate (PET), known within the textile industry as ‘polyester,’ is the most used thermoplastic polymer worldwide. This semi-crystalline and naturally transparent plastic are widely used as an effective moisture barrier with wide-ranging applicability in packaging. Bottling is known as PET resin or PET in these cases.
PET, a naturally colorless material used as fiber for clothing, becomes an engineering plastic when combined with carbon nanotubes or glass fiber. This is done in order to boost the strength of the material.
An Overview of Polyethylene Terephthalate
DuPont chemists in North America first polymerized Polyethylene terephthalate in the 1940s in their quest to develop high-quality polymer or synthetic materials that would be used as textile fibers. This product is made via the synthesis of terephthalic acid and ethylene glycol. DuPont eventually branded the PET fiber as ‘Dacron.’
Today, PET is the original deal for more than half of the world’s synthetic fibers, especially when used for fabric applications.
During the late 1950s, researchers discovered a way to stretch thin extruded sheets in 2 directions conveniently. This resulted in the creation of PET film, which is now employed extensively for packaging, photo, and video films. The early ’70s saw the advent of blow-stretch molding technology used in making PET bottles. By 1973, the polyethylene terephthalate bottle was patented.
How to Make PET
Making polyethylene terephthalate starts with distilling hydrocarbon fuels into lighter groups known as ‘fractions.’ Some of these fractions are combined with catalysts in order to produce plastics, mostly via polycondensation or polymerization.
But regarding polyethylene terephthalate, hydrocarbon ethylene glycol is combined with terephthalic acid in order to produce the final material.
PET is a durable plastic and lightweight material that is strong and doesn’t require additives to increase its strength. When PET is used for packaging, less material is required, and minimal fuel is needed for shipping.
Moreover, even though PET is a petroleum-based material, about 40 percent of the energy is stored internally. This is usually available a second time when the material is recycled. The life cycle studies of PET have systematically shown that the material is highly sustainable and possesses a positive environmental profile.
Global Reports About Polyethylene Terephthalate
According to reports, the prevailing global demand for Polyethylene terephthalate generates an annual market of approximately 56 million metric tons. According to Wikipedia, most of the end users of polypropylene are found in the textile industry and consume up to 60 percent of the total.
Other major uses of PET include the packaging and bottling industry accounting for about 30 percent.
Types of Polyethylene Terephthalate
Different types of polyethylene terephthalate exist today as homopolymers as well as a product modified by copolymers. It is known as PET resin or PET when used for beverage and food packaging and is called ‘polyester’ in the textile industry.
Characteristics of Polyethylene Terephthalate (PET)
Polyethylene terephthalate is differentiated from other forms of plastics due to its characteristics. Here are a few of them:
- Strength to Weight Ratio
Polyethylene terephthalate is an incredibly strong and highly durable plastic despite its lightweight. This is one of the major keys to PET’s energy efficiency as it allows for delivering more products in less packaging.
- Chemical Resistance
PET doesn’t react with water, food, etc., which is one of the primary reasons it is used extensively for packaging consumables.
- Transmissivity
Polyethylene terephthalate is naturally transparent. However, if you desire plastics with higher transmissivity, you may opt for Polycarbonate or Acrylic.
- Shatterproof
PET is so strong that it never fractures or breaks. This makes this plastic an excellent replacement for glass for making containers.
- Sustainability
PET is not only energy-efficient but is highly sustainable, enjoying a much more favorable sustainability profile than aluminum, glass, as well as other materials used for packaging.
PET’s sustainability climbs even higher when recycled. This is because about 40 percent of PET’s energy use is attributed to its resource energy. The resource energy is inherently trapped in its raw materials and can be recaptured and reused via recycling.
Why is PET Such a Durable Plastic?
As mentioned earlier, the building blocks of PET involve the combination of terephthalic acid and ethylene glycol to form a polymer chain, spaghetti-like strands of PET, which are then extruded, cooled quickly, and cut into small pellets.
The resin pellets can be heated until they turn molten and can easily be molded or extruded into any item.
The durability of PET makes it one of the most widely-used durable plastics globally. It is practically shatter-proof, and its extremely high strength-to-weight ratio makes it a viable option for packing water and food. It doesn’t react with food or water, so no one risks getting poisoned.
Global Safety Approval
The FDA and other health-safety agencies worldwide have approved PET as safe for contact with beverages and food. PET doesn’t contain phthalates (plasticizers) or BPA (bisphenol-A).
Extensive studies, testing, and regulatory approvals have guaranteed the safety of PET for beverage, pharmaceutical, food, and medical applications. PET has enjoyed widespread acceptance for over 30 years and still maintains its supremacy over other plastics.
Recyclability
Polyethylene terephthalate is entirely recyclable and is presently the most recycled plastic worldwide and within the United States. Every year, over 1.5 billion lbs. of used PET containers and bottles are recovered for recycling in the U.S. alone.
Anyone can easily identify PET by the #1 within the triangular ‘chasing arrows’ code, which is often molded into the side or bottom of the container. It is the only plastic with this code worldwide.
PET undergoes commercial recycling via washing and re-melting, including a chemical breakdown of its component materials, in order to make a new PET resin. Nearly all municipal recycling program in Europe and North America accepts and uses PET containers.
Products Made from Recycled PET Durable Plastic
Some of the products developed from recycled PET include the following:
- Rope
- Clothing
- Industrial strapping
- Carpet
- New PET jars and bottles
- Construction materials
- Protective packaging, etc.
Conclusion
Within the 60 years since Polyethylene terephthalate was first synthesized, it has beaten all other plastics to become one of the world’s most versatile, most widely used, and trusted materials.
Its durability also plays a crucial role in making it the world’s #1 plastic choice.
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