PET or polyethylene terephthalate is a general-purpose thermoplastic polymer that belongs to the family of polyesters. Polyester resins are known for their good mechanical, thermal, and chemical properties along with their excellent dimensional stability. For this reason, PET polyethylene terephthalate also has the same properties. In this PETROPROVIDERS article, we will talk about polyethylene terephthalate or PET. First, we will review its structure, features, and properties, and then we will provide additional information such as the use of PET and its process conditions.

Full introduction of polyethylene terephthalate and its applications

PET can be converted into fibers, fabrics, wrapping sheets, etc. PET is naturally very flexible, colorless, and semi-crystalline. Depending on the production process, it can be semi-hard or hard. As mentioned, PET has good dimensional stability, also high impact resistance, and good resistance to moisture, alcohol, and chemical solvents.

polyethylene terephthalate Structure

polyethylene terephthalate Structure

The polyethylene terephthalate PET grades available in the markets are unreinforced, glass fiber reinforced, flame-resistant grade, etc. Adding fillers such as glass fibers, carbon nanotubes, etc. helps in strength, final surface finish, etc.

IRAN PET copolymer is also available in addition to its homopolymer. Usually, by modifying the homopolymer, they produce PET copolymers such as PETG or polyethylene terephthalate glycol. Such modifications to PET lead to changes in crystallization and melting temperature of the material.

This widely used substance has received many letters and is also referred to as a trailer in the United Kingdom. PET was first officially registered globally in 1941 by Dr. John Rex Weinfield. Since then, scientists and researchers from Britain and the United States have been able to use the license in 1951. It was in 1952 that “Dr. DuPont” succeeded in registering Miller’s name instead of polyester film pieces.

These changes continued to the point that in Russia and research institutes, this valuable substance was also referred to as Lavosan. Most global PET products are made to achieve a larger volume of synthetic fibers.

Fiber makes up 30% of the equation and plastic bottles 60%. Therefore, in large scientific foundations, the use of this material is preferred to its name and it is generally called polyester.

Polyethylene terephthalate consists of polymerized units of the monomer ethylene terephthalate, the formula (C10H8O4) is repeated in all its units. For this reason, its most important use is reprocessing, and for this reason, its resin number is one.

Resin number one causes this polymer to be produced in two ways each time. These scenarios are optional; They are usually semi-crystalline and completely transparent. Of course, these crystals may be close to transparent depending on their semi-crystalline material, but they usually have some impurities.

How to produce IRAN PET

How to produce IRAN PET

How to produce IRAN PET

Pure terephthalic acid (PTA) is obtained from paraxylene in a process of the same name. In the PTA unit, by oxidizing paraxylene in the presence of air in different stages and finally washing with acetic acid, a product called “pure terephthalic acid” is obtained. The appearance of this product, as its name implies, starts with acid and is in the form of powders in the size of 40 to 200 microns.

In another unit, terephthalic acid is combined with ethylene glycol in a chemical process to form polyethylene terephthalate or PET. The appearance of this product is similar to chips and has different grades. Bottle grade and its fiber grade are produced in the PET unit of petrochemical complexes. These chips are melted in downstream industries and converted into plastic products during chemical processes.

Polyethylene terephthalate resins are commercially produced from ethylene glycol and dimethyl terephthalate (DMT) or terephthalic acid (TPA). DMT and TPA are both solid, DMT melts at 140 ° C while TPA sublimates.

In both processes, 2-hydroxyethyl terephthalate (BHET) -based monomer is also produced, as well as methanol (in the DMT process) or water (in the TPA process). The BHET monomer is then polymerized under low pressure in the presence of catalyst and heat to produce PET.

What is the process of producing PET from dimethyl terephthalate?

Both discontinuous (batch) and continuous operations can be used to generate DMT. There are three main differences between continuous and non-continuous operations, which are:

  1. A column reactor replaces the kettle reactor for esterification.
  2. In continuous operation, reactors without agitators are required.
  3. Different additives and catalysts must be used to achieve the appropriate properties (such as molecular mass and molecular mass distribution).

Key advantages and properties of polyethylene terephthalate

properties of polyethylene terephthalate

properties of polyethylene terephthalate

There is a great variety in the properties of this polymer, depending on the application and the orientation of the polymer chains. This polymer melts at a temperature of about 255 ° C; If cooled rapidly, it becomes almost completely amorphous and its density is approximately 1.38 gr/cm3.

Due to slow molecular motions, crystallization begins at about 80 ° C, and 130 ° C its density increases by 1.42 gr/cm3. With proper orientation and heat application, the density also increases to 1.45 gr/cm3.

This is one of the most important polymers used in various industries. It has very valuable features that have made it very popular. These features include:

  • It has more strength and rigidity than PBT.
  • It is very strong and lightweight.
  • It is known as a barrier against the penetration of gas (oxygen, carbon dioxide) and moisture.
  • It has excellent thermal insulation properties.
  • The temperature range is widely used. (60- to 130 degrees)
  • Compared to PBT, it has a higher HDT temperature.
  • Suitable for applications that require transparency.
  • PET polymer does not break and also has good tear resistance so that in some applications it is a good alternative to glass.
  • PET is considered safe for food contact by many countries and organizations.
  • PET plastic has excellent resistance to glue, hydrocarbons, oils, and greases.
  • It has moderate resistance to aromatic and halogenated hydrocarbons.

Limitations and disadvantages of PET in global industries

Despite the interesting advantages and features of this material, it also has disadvantages. These disadvantages include:

  • It has lower impact strength than PBT.
  • It has a lower moldability than PBT because it has a lower crystallization rate.
  • Boiling water has a destructive effect on it.
  • It is weak against strong bases.
  • PET is weak against ketones, aromatic and halogenated hydrocarbons at temperatures above 60 ° C

Glass transition temperature in polyethylene terephthalate (TG)

Glass transition temperature in PET

Glass transition temperature in PET

The glass transition temperature is the temperature at which the polymer takes on a hard and brittle state at lower temperatures, and this temperature depends on the degree of crystallinity for each particular polymer. A polymer that has no crystalline region is called amorphous.

Increasing the crystalline regions changes the properties of the polymer, such as its strength. For example, in the production of bottles, the method of tensile pneumonia is used, which causes crystallization and increases the strength and stability of the polymer. For PET in the amorphous state, the glass transfer temperature is equal to 67 ° C and in the crystalline state, it is equal to 81 ° C.

An alloy of polyethylene terephthalate or PET with other polymers

PET alloying with thermoplastics and thermosets is to produce materials that achieve better performance and properties for the desired consumption at a lower cost. PET alloys include polyethylene, polypropylene, polycarbonate, polystyrene, ethyl vinyl acetate, and ABS. Also thermosets such as epoxy, polyester resin, phenolic resin, etc.

PET alloy of polyethylene terephthalate with fiber-reinforced polyolefins is common for use in injectable parts of the automotive industry. PET / PC alloy is also used in cases that require a combination of excellent stiffness properties, heat and chemical resistance, impact resistance, high tensile strength, and flexural strength.

PET alloys and thermosets are also used to improve thermal, mechanical, impact, and flammability properties. These alloys are used in automotive, aerospace, and electronic components.

The main applications of polyethylene terephthalate

manufacture PET bottles

In general, this polymer is used to produce a variety of durable plastics, bottles, sheets, belts, and mechanical parts. PET bottles are used to package a wide range of products, including mineral water, carbonated beverages, vegetable oils, pharmaceuticals, and health and beauty products. The use of these bottles has become very important; Because they have little harm to human health.

PET is used in the packaging industry in several different forms, which are mentioned below:

Application of this material in the automotive industry

PET is a successful polymer in the automotive industry that has many applications. Such as wiper, gearbox, headlight clamp, engine cover, etc.

Production of plastic bottles (beverages, mineral water bottles, etc.) with PET

These are used to make plastic bottles; Because it resists the penetration of water and moisture.

Production of PET films:

Production of plastic tapes due to high mechanical strength

Food packing:

Due to its hygienic, chemical resistance, and other physical properties, PET is used for packaging all kinds of food.

Application of polyethylene terephthalate for packaging and disposable containers:

PET sheet due to having the properties mentioned above, is used in the production of various containers such as trays, disposable packaging containers, pre-made, etc. by thermoforming and vacuum forming.

Use of PET in the textile industry:

Polyethylene terephthalate monofilaments are used to make fibers and various products in the textile industry. PET is widely used in the textile industry. Polyester fibers are strong, lightweight, resistant to tearing and stretching, and therefore have many applications in the textile industry.

Electrical and electronics industry:

PET is widely used in the electrical and electronics industry due to its good electrical insulation properties, excellent dimensional stability, and high strength. PET is an effective polymer in replacing insulation in this industry.

How is PET recycled?

PET recycling

PET recycling

Products made of polyethylene terephthalate are 100% recyclable and the most recycled plastic in the world is PET. The PET recycling symbol is also numbered 1.

Bottles and other used PET products are collected, then washed in them. If necessary, chemical corrections are made to break the PET into small pieces. After this chemical modification, all volatiles and impurities must be removed.

These recycled and shredded PET materials can be used in various industries such as carpet fibers, some carrying bags, wool jackets, films and sheets, belts, etc.

Production of polyethylene terephthalate and its global market

The global production capacity of polyethylene terephthalate was 3.30 million tons in 2017. Among all countries in the world, China has the highest production, which is equivalent to 8.30% of the total global production of this product.

The Asian region, except China, accounts for 21% of production. The North American region accounts for 9.16 percent of production, with the United States having the highest production of any country in the region. The new PET plants are MG Chemical of Corpus Christi and Texas US, with an annual production capacity of about 1.1 million tons. The production capacity of the European region is about 7.14%, South America 1.4%, and Africa 3.2%.

There are only a few companies that produce PET. The figure below shows the five largest companies with the largest production capacity. As you can see, Indorama Ventures has the highest production in 2017 with an annual production capacity of 2.4 million tons.

China is not only the largest producer of this substance but also its largest consumer! The consumer market for polyethylene terephthalate resin is controlled by beverage bottles, films, and sheets. Water bottles have the highest consumption of this product with about 3.26% and the second rank is related to bottles of carbonated beverages with 1.26%. Other major uses of this product include film and sheets (8.13%), food (1.9%), and non-food items (1.6%).

Summary of the study of polyethylene terephthalate and its applications

The most common thermoplastic polymer resin that has many general applications is polyethylene terephthalate (PET). It belongs to the family of polyester polymers. Polyester resins are known for their excellent combination of properties such as mechanical, thermal, chemical resistance as well as dimensional stability.

PET is composed of polymer units of ethylene terephthalate monomer with repeating units (C10H8O4). PET is one of the most recycled thermoplastic materials and has the number “1” as the symbol of recycling.

This polymer is used to produce a variety of bottles, sheets, belts, and injection parts. PET bottles are used to package a wide range of products, including mineral water, carbonated beverages, vegetable oils, pharmaceuticals, and health and beauty products. Today, these bottles have found a very unique place in the packaging industry.

Recycled PET can be used in the production of fibers, fabrics, packaging sheets, and auto parts. Chemically, polyethylene terephthalate is very similar to polybutylene terephthalate (PBT).

The advantage of using PET bottles is that the bottle lid can be opened easily and can be closed again, and they are also lightweight and inexpensive. PET inherently has the characteristics of biodegradable plastics. In two years, more than 30% of it is destroyed underground, which is a more suitable solution to recycle PET and turn it into consumer products.

Although these materials make up a small percentage of the total waste of the community (about 7%), due to their low density, they contain a high volume of about 30% of the total waste. Typically, about 800 kg of waste is disposed of per cubic meter of landfill; While one cubic meter of landfill can only hold 35 kg of bottles.

Like HIPS polystyrene and GPPS polystyrene, it is used to make a variety of plastic products. In addition, same as dioctyl phthalate and phthalic anhydride, it is toxic and harmful to human health and the environment.

What do you think about this important and valuable material? In the comments section, you can ask your questions from our experts. If you find this article useful, please send it to your friends.

What are the most important applications of polyethylene terephthalate?

This is one of the most important polymers used in various industries. The most important applications of PET are Food packing, Production of PET films, automotive industry, textile industry, electronics industry, etc...

Is the use of polyethylene terephthalate harmful to human health?

Yes! This substance contains phthalates, which are very harmful to skin health. In addition, it is carcinogenic and is very harmful to pregnant women. In addition, PET inhibits the endocrine.

Is it safe to use PET plastics?

Yes! Once turned into plastic, it is no longer harmful and can be used in global industries. The FDA has approved the use of PET plastics.

What are the benefits of using PET in global industries?

Polyethylene terephthalate has great advantages; These benefits have led to the popularity of this material in global markets. Like: lightweight, strong, thermal insulation, high HDT temperature, transparency, tear-resistance, and safe for food contact.

What are some examples of polyethylene terephthalate?

Water bottles, soft drinks, soap, and toothbrushes are examples of PET materials in everyday life.

What are the risks of using PET?

If heated, it can produce toxic fumes, be dangerous to the stomach, and cause respiratory problems.

Is it safe to use PET for food packaging?

Yes! It is FDA approved and is used for food packaging.

How to buy the best polyethylene terephthalate?

At PETROPROVIDERS, we offer you the best PET. You can contact our specialists to buy IRAN polyethylene.

What are the most important products made of polyethylene terephthalate?

This material is used to produce a variety of packaging and bottles and plastic products.

Is PET harmful to the skin?

This chemical can be harmful to the skin; Causes skin allergies or itching.