What is PET Plastic?
Polyethylene terephthalate, better known as PET Plastic (also sometimes as PETE ), is the most used thermoplastics globally with various textile, films, electronics, packaging, automobiles, etc. The biggest utilizer of PET is the textile industry, in which thermoplastic is mostly known by the name Polyester. It has a fantastic set of different properties, making it very attractive for manufacturers like chemical, mechanical, thermal resistance, and dimensional stability.
It is semi-crystalline in nature and colorless. Some of the important properties include water resistance and toughness (the strength to weight ratio is impressive). The material is virtually shatterproof, which improves its applicability by many nautches.
PET plastic is also highly recyclable (which we’ll discuss later in the article ) and has the number “1” as its recycling symbol.
According to many worldwide reports, PET, with an annual production of 56 metric tons, is the most used thermoplastic in the world. The textile industry consumes approximately 60% of that, and other major consumers include the packaging and bottling industry with 30%.
PET Copolymers –
PET or PETE is originally a homopolymer but can be modified to produce copolymers ( polyethylene terephthalate glycol-modified ) depending on the application.
The commonly used modifiers to produce PETG are cyclohexane dimethanol (CHDM) and isophthalic acid, respectively.
These polymers predominantly react with crystallization, thereby changing or lowering the polymer’s temperature.
PET Characteristics –
PET or polyethylene terephthalate has many consequential properties. Let’s talk about them.
Chemical Resistance: PET has a significant amount of resistance towards water, food, and natural cause like bacteria, fungi, etc. That makes it compatible with food packaging applications.
Transmittance: It is naturally transparent. However, it doesn’t look exciting compared to other high transparent polymers like Polycarbonate and Acrylic. If high transparency is required, these polymers should be used instead of PET.
Shatterproof: PET plastic is solid and strong. It is virtually shatterproof and thus used as an alternative to glass.
Polyethylene terephthalate is originally a thermoplastic, and it is decided by the way it reacts to heat. However, there are many variants of polyesters that are considered thermosets.
The major difference between thermoplastics and thermosets can be attributed to how they react to heat. Thermoplastic melts at its melting point ( 260°C for polyester ).
The major benefit of any thermoplastics when it needs to be processed in injection molding is that when it melts, the liquid form can be cooled and reheated without large degradation.
On the contrary, thermosets can only be burned once as the first heating changes their chemical nature that cannot be reversed.
Once their chemical nature is changed, any additional heating will burn the polymer—That’s one of the main reasons for thermosets being poor candidates for recycling.
|Coefficient of friction||0.2 – 0.4|
|Tensile modulus ( GPa )||2 – 4|
|Tensile strength ( MPa )||
80, (for biax film 190 – 260)
|Hardness – Rockwell||M94-101|
|Izod impact strength ( J.m-1 )||13 – 35|
|Limiting oxygen index||21%|
|Refractive index||1.58 – 1.64|
|Water absorption – equilibrium||<07%|
Water absorption – over 24 hours
|Refractive index||1.58 – 1.64|
|Density ( g.cm-3 )||1.3 – 1.4|
|Working temperature ( °C )||115-170|
|Specific heat ( J.K-1.kg-1 )||1200 – 1350|
|Thermal conductivity ( W.m-1.K-1 )||0.15 – 0.4 @ 23|
|Heat-deflection temperature – 0.45 MPa ( °C )||115|
|Heat-deflection temperature – 1.8 MPa ( °C )||80|
|Coefficient of thermal expansion ( x10-6 K-1 )||20 – 80|
How is PET Made?
For PET Plastic, like other thermoplastics, the making process starts with hydrocarbon fuels filtration into smaller parts called “fractions.”
A certain amount of extracted fractions can be combined with catalysts to produce plastics—the process is called polymerization or polycondensation. The only and major difference for PET is the combination of hydrocarbon ethylene glycol and terephthalic acid.
Processing Conditions for PET Plastic –
PET is perfectly compatible with injection moulding, Blow Molding, Extrusion Molding, and 3D Printing processes. The general use for PET plastic is extruding produce films and sheets.
It is advisable to dry polyethylene terephthalate for up to 2-3 hours before processing.
|Injection Molding||Blow Molding||Extrusion Molding||3D Printing|
|Melt temperature – 280-310°C.||Melt temperature – 200 to 245°C||Extrusion temperature – 270-290°C||
Advised temperature – 40 and 260°C
|Mold temperature: 140-160°C||Mold temperature – 10-50°C||NA||
Bed Temperature – 100°C
|Most preferred for transparent applications.||Blow Molding is commonly utilized for manufacturing transparent bottles.||PET can be utilized to produce films and sheets, which can be thermoformed later.||
Most preferred to manufacture products with complicated geometries like toys, gifts, and novelty items.
The recommend screw L/D ratio is 18-22.
|NA||Extrusion speed around 100 RPM||
Retraction speed should be slow at 30mm/s or less.
- Because PET has phenomenal water and barrier resistive properties, it is often used to manufacture plastic bottles for mineral water, alcohol, and carbonated drinks.
- Non-Oriented PET is often thermoformed to produce packaging trays and blisters.
- Its Rigidness and fabulous mechanical strength make it a prime choice for manufacturing tapes.
- A range of physical properties coupled with chemical inoperativeness makes it compatible with food packaging applications.
- Polyester is one of the most polymers within the textile industry.
- The packaging industry is also very dependent on PET for microwave containers, rigid jars, transparent films, sheets, etc.
Advantages and Disadvantages of PET –
- PET possesses a high strength-to-weight ratio (a rare quality to found). Thus, easy and inexpensive to transport.
- It is available in abundance and is inexpensive compared to other thermoplastic.
- It is moisture resistant.
- It shows fantastic electrical insulating properties.
- PET is smack and fracture proof, making it a good alternative to glass in many applications.
- It exhibits high resistance to organic matter and water, which can become advantageous or a nuisance depending on the application.
- PET is approved to be safe with food and beverages. Agencies like FDA, Health Canada and EFSA have given it a free flag.
- Polyethylene terephthalate can be recycled. Recycling includes a series of washing processes; after that, it can be reused.
- It is transparent to microwave radiation.
- Compared to its closest competitor, Polybutylene terephthalate (PBT), PET shows higher heat distortion temperature (HDT).
Polyethylene terephthalate comes with great qualities, and the positive obviously outshine the negatives, but we should still look at them.
- PET is not biodegradable
- PET is somewhat vulnerable to oxidation (But nothing is rock solid proof about this).
Recycling of PET Plastic and its Effects on the Environment –
Polyethylene Terephthalate is a 100% recyclable material, and to its credit, is the most recycled thermoplastic in the world.
The recycling code “1” says it all.
The low diffusion coefficient is the prime reason for PET to be the best when used recycled material.
The used PET products are collected and stored using a special process and goes through a kind of washing or chemical process to break them down into small pieces called PET flakes. Manufacturers use these recycled PET flakes for strapping, films and sheets, Food and beverages containers, carpets, flee bags, etc.
1. Which Plastic material is better? PET or Polycarbonate?
Ans. Both PC and PET have their pros and cons. Polycarbonate has better catch resistance and is easier to wash, but PET resin is cheaper than polycarbonate; however, that doesn’t necessarily translate into good profits as equipment to process PET bottles are more expensive.
2. Which Plastic material is better? PET or Polypropylene?
Ans. Both plastic materials are heavily utilized in the plastics processing industry, and they have advantages and disadvantages. Talking about PET, its products have slightly better impact resistance than products made from polypropylene. In addition, PET containers are often regarded best for maintaining the taste and aroma of food, thanks to their great oxygen barrier properties. On the other hand, PP containers fare better in mositiure, alcohol, and chemical resistance.
3. Why is PET easier to recycle than PP?
Ans. PET is easier to recycle than PP because its polymer chain breaks down at a relatively low temperature. As a result, there is minimal degradation of the polymer chain during the recycling process. On the other hand, degradation with PP during the recycling process is more fierce, resulting in more difficulties in recycling.
4. At what temperature do plastic bottles melt?
Ans. PET bottles usually melt at a temperature of 255 degrees Celsius (491 degrees Fahrenheit).
5. How many times PET bottles can be recycled?
Ans. New scientific studies conducted in the US show that PET and HDPE bottles have a significant market share in the American bottling industry and can be recycled at least 10 times.
Final Thoughts –
Finally, I would like to say that PET plastic, along with its few variations, is useful for any plastic manufacturer. Adding them to your business would help you bring down the costs substantially and shoot your profits sky-high.
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Have a fantastic day 🙂