PET vs Other Plastics: What’s the difference?
As concerns about the environmental impact of plastic waste continue to grow, businesses and consumers alike are looking for ways to reduce their plastic consumption and choose more sustainable options. PET (polyethylene terephthalate) is a type of plastic that is commonly used for packaging, but how does it compare to other types of plastic packaging in terms of environmental impact, recyclability, and safety? In this article, we will explore the key differences between PET and other types of plastic packaging and why PET is the clearly the best solution.
TSS Thermalist
June 5, 2023 | Innovation
As concerns about the environmental impact of plastic waste continue to grow, businesses and consumers alike are looking for ways to reduce their plastic consumption and choose more sustainable options. PET (polyethylene terephthalate) is a type of plastic that is commonly used for packaging, but how does it PET vs other plastics compare in terms of environmental impact, recyclability, and safety? In this article, we will explore the key differences between PET and other types of plastic packaging, and why PET is the clearly the best solution.
What are common types of plastic packaging?
Types of plastic produced in 2015 (by tons)
Low-Density
Polyethylene (LDPE)
LDPE is a common plastic and is resistant to oils, acids, and bases. It’s food-safe, and because it’s flexible yet rigid, it’s commonly used in produce bags, condiment bottles, and heat-sealed packaging. While LDPE can be recycled, it requires an enormous amount of energy to produce and is not a sustainable option.
High-Density
Polyethylene (HDPE)
Translucent, durable, and resistant to chemicals and solvents makes HDPE the most widely used plastic for packaging. It has a high tensile strength, which makes it able to withstand high temperatures. It’s commonly used in products like plastic beverage bottles and cereal box liners. Like LDPE, HDPE takes a large amount of energy to produce, making it an unsustainable option.
Polypropylene (PP)
PP has a high melting point and low moisture transmission, which makes it a common option for hot liquid packaging. It’s also used in yogurt containers, take-out containers, and bottle caps. It is, however, susceptible to UV light.
Polyvinyl Chloride
(PVC, Vinyl)
PVC is among the most produced plastic in the world because of its oil-and chemical-resistant properties. It is also a very stable plastic, making it durable and clear. PVC is used in everything from meat packaging, to clamshells, and blister packs. PVC is one of the most unsustainable packaging options, and there are concerns that manufacturing it produces toxic by-products.
Polystyrene (PS) and
Expanded Polystyrene (EPS)
Polystyrene is rigid, stiff, insulating, and moisture resistant. That’s why it’s often used in single-use cutlery, egg cartons, and meat trays. Styrofoam is a type of polystyrene known as expanded polystyrene. It has a very low recycling rate, and it’s UV-degradable and highly flammable.
Polyethylene
Terephthalate (PET)
PET belongs to the thermoplastics family and is known for its strength and stiffness. It can be easily molded into various shapes and sizes by heating, melting, and cooling. It’s lightweight, clear and food-safe, and it’s the most sustainable plastic packaging option.
Polyphthalamide (PPA)
PPA belongs to the nylon family and is a high-performance resin that possesses outstanding thermal, mechanical, and physical properties. Most PPA grades are filled with glass or minerals. Due to its cost-effectiveness, PPA is often used in applications that would otherwise require more expensive thermoplastics or metal.
Polyurethane (PUR)
PUR is a widely used polymer for creating foam, specifically for furniture and packaging applications. Its open-cell structure is elastic and relatively soft, making it highly versatile for various purposes, particularly for fragile and lightweight objects or those that are sensitive to vibration.
What’s the difference between PET and other types of plastic?
Ethylene Glycol
Terephthalic Acid
Polymer Chain
Extrusion
Cut into Pellets
Heated and Molded
PET, which is a polymer chain, is formed by combining ethylene glycol and terephthalic acid, which are its fundamental building blocks. After extrusion, the PET strands look like spaghetti and are rapidly cooled before being cut into small pellets. The resin pellets are heated to a molten state, allowing them to be extruded or molded into practically any shape.
Properties of PET
Physical Properties
Density: 1.3 – 1.4 g/cm3
Water absorption (equilibrium): less than 0.7
Thermal Properties
Upper working temperature: 115 – 170⁰C
Mechanical Properties
Tensile Modulus (GPa): 2 – 4
Processing Properties
Melting Point: 260⁰C
The biggest difference between PET and other types of plastic is PET’s high recyclability and sustainability. Unlike plastics, PET is not single use. In fact, it is 100% recyclable and can be recycled into new products over and over again.
PET can be recycled back into its original uses when collected in a pure state, and there are methods available to break down the polymer into its chemical precursors for resynthesizing into PET.
Additionally, PET has a lower carbon footprint compared to other plastics as it uses less energy during manufacturing. It is also lightweight, making it an economical choice for businesses looking to reduce transportation costs and carbon emissions.
Plastic produced by use
Is PET actually sustainable?
Although we encounter PET daily, the mere mention of “plastic” or “PET” often invokes negative connotations due to its perceived link to environmental destruction. In reality, PET is the most recyclable plastic.
Government agencies around the world regulate and provide scientific guidance on any health risks associated with food and beverages. PET has been deemed safe for contact with food and beverages by organizations such as the Food and Drug Administration, Health Canada, and the European Food Safety Authority. If you remain unsure, consult your local food and beverage agency’s guidelines on the use of PET containers for edible products.
The Association of Plastic Recyclers has laid out practices and protocols regarding PET, can be found below.
Down to specifics
PET Standard Laboratory Processing Practices
The general term PET is used so that these practices can apply to any molded part made from PET. In practice, molded articles are expected to be packaging materials such as injection stretch blow molded bottles, extrusion blow molded bottles and thermoformed PET sheet stock. Testing can be employed with a PET molded article alone, or to evaluate the impact of design features such as closures, labels, or additives, for example, on recycling. These practices can also be used to evaluate PET virgin resins in the form of pellets.
rPET-to-Sheet Protocol
Today, considerable amounts of both recycled bottle flake and pellets are converted into sheets. Most of the sheet is thermoformed and is used in many applications such as food, electronic, pharmaceutical, and other types of packaging.
Recyclable content can range from 0 to 100% of rPET for any of these applications. The recycled material can be in the form of bottle flake or pellets. Most applications do not require the material to be solid stated. The most critical case is then the use of 100% bottle flake or pellets.
In the scope of this rPET-to-Sheet Protocol, the test sample blends, which will be converted into sheet, need to be made using the washed and dried Control and Innovation flake samples or non-solid stated extruded pellets that are produced from the PET-CG-01 test. Note that both the Control and Innovation samples must be in the same form (either flake or pellet) for testing. The reason for this is to simulate the sheet extrusion process that directly extrudes flake or pellets at a 50% by weight blend level. The melting of the material in the extruder can have a significant influence on the process and the difference in shape between a pellet and a flake is a major factor. Furthermore, crystallizing and drying a pellet or a flake could generate some different types of problems. Thus, preferably the test samples should be in the form of flake. However, since a considerable amount of rPET is also converted into sheet from pellets, this test does allow for the use of pelletized rPET where flake may not be available.
The rPET-to-Sheet evaluation program is designed to show processing and unoriented sheet performance differences between a control material and that control material containing recycle-content Innovation material. It is a comparative study that does not rely on the final sheet meeting absolute performance criteria.
Flow Diagram for rPET-to-Sheet
Labels for PET – Wash Water Evaluation
When PET packaging is recycled, it is critical that inks and adhesives used with labels are compatible with the PET recycling process. Most important is that inks and adhesives are not a source of contamination that can lead to discoloration of recycled PET. It is important too that inks and adhesives are developed to have minimum impact on wash and wastewater in terms of supporting the objectives and using less water and reducing wastewater disposal costs.
1.
One liter of wash water
2.
Visual Evaluation
3.
Settling Evaluation
4.
Screen Filter Evaluation
5.
Fine Filter Evaluation
6.
Report
Inks and adhesives used in PET packaging applications have undergone substantial innovation, with a focus on how these materials affect the recycling process and the appearance of wash water produced during PET recycling.
- Hot Caustic Resistant Inks – Inks and labels purposely developed and tested so inks remain fully adhered on the label during the hot caustic wash, and the label inks do not discolor PET flake and injection molded plaques made with washed PET bottle flake.
- Wash-Off Inks –Inks purposely developed and tested to wash off cleanly from the label or PET package and not discolor PET flake and injection molded plaques made with washed PET bottle flake. Further, the inks are engineered to wash off the label as fragments, tens of microns in size, that can be readily filtered from wash and wastewater.
- Incidental Wash Water Discoloration/Incidental Inks – Inks are resistant to hot caustic and remain adhering to the label film but may create some incidental tint color to the wash water from pigments that are slightly soluble in hot caustic, or from ink abraded from cut edges. Incidental ink is not a concern when there is no plaque discoloration.
- Free adhesive – A variety of adhesive types can be used to fix labels onto a PET container. If those adhesive washes off both the PET surface as well as the label surface it becomes free and mixes with the hot caustic wash water. The adhesive might float to the surface, be suspended in the wash water, or sink and mix with the washed PET flake.
- Bound Adhesive – Adhesives designed to remain adhered to the label film and so not mix with the wash water.
Why does TSS use PET instead of other types of plastic?
We use PET for Renewliner and RenewMailer because while other types of plastic can be recycled, only PET can be infinitely recycled in a closed-loop cycle. PET’s high strength-to-weight ratio is a significant contributor to its energy efficiency, enabling more products to be transported using less packaging and fuel.
While all PET should be recycled, PET products that wind up in in landfills do not present any risk of harm or leaching because the polymer is inert and resistant to degradation by microorganisms. Additionally, PET containers are easily flattened, taking up minimal space in landfills.
Compared to other plastics, PET is lightweight, durable, thermally secure, food- and pharmaceutical-safe, and as cost-effective as Styrofoam. When you use PET, no adhesives, PVC, paper, or contaminants are introduced to the recycling stream.
100% Recyclable
Lightweight
Thermal Security
Lower Carbon Emissions
Non-Reactive
BPA-Free
Water-Based Ink
