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PET Recyclability: A Blessing for the Environment

////PET Recyclability: A Blessing for the Environment

Car battery with green recycle sign.

Polyethylene terephthalate (PET) plastic is popularly known as the clear plastic. It is used to manufacture water and soda bottle. At present, seventy percent soft drinks (carbonated drinks, still and dilatable drinks, fruit juices and bottled water) are being packaged in PET plastic bottles. The rest (30 percent) comes mainly in glass bottles, metal cans, and cartons.

PET’s recyclability is the most outstanding quality. It is 100% recyclable and it is globally known as a safe, non-poisonous, strong, lightweight and flexible material.

In the United States, the recycling companies are able to recover about 1.3 million pounds PET bottle each per. They use them (recovered bottles) for recycling purpose. Consequently, the PET bottle has become the most recyclable product in America.

Car battery with green recycle sign.

PET can be identified by the number “1” in the small triangular symbol that is molded into the bottom or side of the container.

PET can be recovered and recycled unlimited time thorough washing and re-melting or by chemically breaking down. These PETs are used for the new product.

Some PETs are unable to recycle. Because they are so unhygienic that cannot be purified. These are burned safely. Those burning PETs are one of the major sources of energy. They are called “Thermal Recycling’.

Application of PET

robot with trashFor producing bottle and container, PET is used as raw material. It is used for producing plastic water and soda bottles, food packaging for cakes, cut fruit, and salads and as retail blister and clamshell packaging for cosmetics, razors, and toys.

It can also be used in containers for peanut butter, shampoo, and salad dressings and for carpeting, clothing, sleeping bags and much,

PET is recycled into a new industrial strapping, automotive parts, construction materials, even the felt for tennis balls, and tennis ball canisters.

In short, it is applied to manufacture a large number of containers used for packaging food product and consumer goods. Therefore, it is considered as the most common consumer plastic.

Collection of PET

robot with trashIt is a challenging task to collect PET bottles for recycling. There is no uniform collecting system. Different countries and different agencies follow diverse collecting models. The most challenging part is to create awareness among the people. The concerned authority faces critical situation to organize a collective system for household wastes.

The consumers discard PET packaging after the use. This is called “post-consumer PET” by the recycling industries.

Different agencies including local government start to collect “post-consumer PET”. The PETs are separated from other household wastes. In some countries, separate containers are provided to keep PET.

How PET collection can be increased?

  • Attempts must be taken to continuously raise consumer awareness on the importance of PET bottle collection.
  • All direct communication channels such as the label, advertisements, internet and sponsored events, to disseminate educational messages must be utilized.
  • The public and the professional association campaigns that aim to encourage bottle collection must be bolstered.
  • Local Communities must be engaged in continuously working to improve collection capacity besides the local government and professional associations initiatives
  • Coordinated efforts with public authorities are necessary to improve the current collection scheme or initiate a new program.

Sorting of PET

After collecting the PETs, these are accumulated in authorized center or handed over to the original sellers.

They take the collected post-consumer PET to the recycling center. The recycling center is known as materials recovery facilities (MRF).

MRF employees start to sort and separate the PET from other materials, objects (made of PVC, HDPE, polypropylene etc like) rigid plastics. The PETs are also separated from that flexible plastic which is used producing low-density polyethylene bags. Drink cartons, glass etc -those are made of non PET -are separated completely.

Sometimes, separation may be conducted on the basis of color fractions. The post-consumer PET is sorted into different color fractions: transparent or uncolored PET, blue and green colored PET, and the remainder into a mixed colors fraction.

Plastic drinks bottles are often produced through a mixture of polymers, typically a mix of PET and PP or PVC. Numerous methods are applied for the separation.

To separate PET from any PP in the bottle, ‘sink-float’ separation technique is used. PET is denser than PP, with respective specific densities of 1.43-1.45 g/cm3 and .93-.95g/cm3, so PET will sink in a tank of water. On the contrary, PP will float. In this way, separation can be made.

Unfortunately, when PET is mixed with PVC, it can be very difficult to separate one from another. They have similar specific gravities and also look similar to the human eye.

Since a small amount of PVC in a batch of PET can ruin a melt, it is obligatory to separate the PVC. In this case, Near Infrared Radiation (NIR) techniques can be used. But darkly colored plastics absorb the radiation; therefore, the distinction cannot be made.

Polyethylene terephthalate (PET) is a general-purpose plastic. It is manufactured by polycondensation of PTA with ethylene glycol (EG). This material belongs to numerous marvelous properties, for instance, resistance to heat and cold, transparency, electrical qualities, chemical proof and abrasion proof. Consequently, a wide variety of applications in the fibers, PET bottle and films are identified.

PET is a thermoplastic polymer. It can be both opaque and transparent, depending on the exact material composition.

PET is produced from petroleum hydrocarbons. A reaction between ethylene glycol and terephthalic acid is required.

At first, the PET is polymerized to create long molecular chains. It is necessary to produce plastic bottles.

Polymerization is a complex procedure. There are two types of impurities are produced during polymerization. These are diethylene glycol and acetaldehyde.

Generally, Diethylene glycol is generally not produced in high-enough amounts to affect PET but acetaldehyde can be produced not only during polymerization but also during the bottle manufacturing process.

After manufacturing the plastic, it is high time to manufacture bottle. The bottle manufacturing process is as follow.

Stretch blow molding is the first step of bottle manufacturing process. The PET is heated and placed in a mold, where it assumes the shape of a long thin tube. The process by which the plastic is forced into the mold is called injection molding.

The tube of PET (called a parison) is then transferred into a second, bottle-shaped mold.

A thin steel rod (called a mandrel) is slid inside the parison where it fills the parison with extremely pressurized air, and stretch blow molding starts. Consequently, the parison is blown and stretched into the mold because of the pressurized air, heat, and pressure, and finally, assumes a bottle shape.

Car battery with green recycle sign.The mold needs to be cooled relatively quickly so that the newly formed component is set properly.

There are two types of cooling methods. They are direct and indirect. They can effectively cool the mold and the plastic.

Direct method refers to using pressurized air or carbon dioxide directly on the mold and plastic. On the other hand, in the indirect method, water can be coursed through pipes surrounding the mold, which cools the mold and plastic.

When the bottle is cooled and set, it becomes ready to be removed from the mold.

If a continuous molding process is used, the bottles will need to be separated by trimming the plastic. If a non-continuous molding method is used, sometimes excess plastic can seep into the mold during manufacturing and will require trimming.

Since the bottle is removed from the mold and excess plastic is removed, the bottles are ready for transportation.

Generally, PET is easy to be recycled since the polymer chain breaks down at a relatively low temperature. This allows PET to be recycled unlimited times before it becomes unusable. Only contamination can reduce the number of ‘closed loop’ cycles of the PET.

Steps of PET Recycling

Although all PET industry does not use a uniform process of recycling the PET, the general steps of PET recycling are as follows.

  • At first, bottles are sorted by hand and unwanted materials are removed. As a result, only bottles are left. Sometimes, the bottles can be sorted using an automated system.
  • Then the bottles are cleaned to remove any residual liquid or dirt. It helps to prevent contamination.
  • After that the bottles are sorted infrared radiation techniques, to define the type of polymers presented here.
  • When bottles are sorted by color- traditionally blue, natural, green and mixed, it adds additional value to the plastic.
  • Next, the bottles are shredded into flakes which are then washed again. Alternatively, the shredding step is skipped and the bottles are melted and reformed into a different shape.
  • Finally, the shredded plastic is melted to produce plastic granulates, or pellets.

PET Bottle is Use Safe or not?

When the plastic bottles are made from polyethylene terephthalate (PET), these are safe and reusable. They have usually a Plastic Identification Number (PIN) #1. The reusable plastic identification numbers are #2, #4, #5.
There are seven Plastic Identification Numbers (PICs). Each of them contains reusing and recycling information. These are

  • #1 – PET (Polyethylene Terephthalate)
  • #2 – HDPE (High-Density Polyethylene)
  • #3 – PVC (Polyvinyl Chloride)
  • #4 – LDPE (Low-Density Polyethylene)
  • #5 – PP (Polypropylene)
  • #6 – PS (Polystyrene)
  • #7=others

The Environmental Benefits of Recycling PET

robot with trashPET has become an extremely useful substance and its use has skyrocketed in the last few years. Since the market for bottled water has increased, the demands of PET also increased simultaneously.

In Britain, approximately 15 million plastic bottles are being used every day.11% of household waste is plastic, and around 40% of this is plastic bottles.

To produce one volume of a PET bottle, the energy consumption is around 5.4 MJ/ liter. It is a much less than glass or aluminum.
Recycling of PET helps to decrease the dependence on oil and gas. It also reduces landfill waste and diminishes greenhouse gas emissions into the atmosphere.

Around 4% of world oil is utilized to make all plastic. In the UK, 37% of plastic is used to make packaging. Of this packaging, only 1.2% of plastic packaging is used to make PET plastic drinks bottles.

The PET industry is constantly looking for ways to reduce the use of the amount of water. It uses a small amount of water in its manufacturing processes.

Conclusion

robot with trashThe basic building blocks of PET are ethylene glycol and terephthalic acid. They are combined to form pellets of PET. More clearly, when the two raw materials of PET are accumulated under high temperatures and low vacuum pressure, long chains of the polymer are formed.

Although previously, PET plastic water bottles have been considered as safe, at least as far as human health is concerned, new evidence suggests that PET, or polyethylene terephthalate may not be so safe as considered.

PET is one of the most commonly used plastics in consumer products. It is used in producing most water and pop bottles, and some packaging. PET plastic is complicated to decontaminate. Proper cleaning requires rooting out detrimental chemicals.

PET plastic is recyclable. About 25% of PET bottles in the US are being recycled nowadays. The plastic is crushed and then shredded into small flakes. These flakes are then reprocessed to produce new PET bottles or spun into polyester fiber.

This recycled fiber is used to create textiles such as fleece garments, carpets, stuffing for pillows and life jackets, and similar products.

In the environmental perspective, PET is more eco-friendly as there is a low amount of water and oil used in producing PET bottle. Moreover, a large amount of landfill is being saved in this way. In addition to, it helps to conduct a proper waste management procedure. As waste management is one of the burning issues in today’s urban planning, PET’s recyclability imputes the human being, the city mayors and the commissioners and other concerned authorities for some extent in waste management.

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2018-10-10T06:09:06+00:00By |Categories: PET, Plastic, Recycling Material|0 Comments

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