Plastic Recycling Symbols Explained: What the Triangle and Numbers 1–7 Mean
It is easy to misread the numbers inside the plastic recycling triangle. Many people think the number shows how many times the plastic can be recycled (it does not), or that it marks where a bottle or jerrycan can be cut open. Others assume the symbol means the plastic will definitely be recycled, which is not true either.
So before we explain what the triangle and each number mean, here are a few short facts about the recycling symbol.
Interesting Facts About the Recycling Symbol
1. The recycling symbol is a Möbius loop. A Möbius loop is a band with only one surface: if you draw a line along it with a pen without lifting your hand, you come back to where you started. The recycling Möbius loop is made of three arrows that form a triangle, and each arrow has its own meaning, which we explain below.
2. The symbol does not necessarily mean the plastic is actually recycled. Sometimes recycling a plastic costs more than producing it new. Only a small share of the world’s plastic is recycled today, and most of it ends up in the environment. One reason recycling is expensive is the cost of collecting the plastic, so by collecting and separating plastic from our rubbish we can do a lot for the environment.
3. Certain additives, such as antioxidants, help keep the recycling process under control. Every round of recycling weakens the properties of the polymer, so the right additive can extend how many times a plastic can be recycled.
4. The number inside the triangle is called the resin identification code. It shows what the plastic is made of, which makes identifying plastics for recycling much easier. Plastics marked 3 and 6 can be toxic, and type 7 plastics are often, though not always, of lower quality.
5. The resin identification codes were introduced by the Society of the Plastics Industry, which renamed itself the Plastics Industry Association in 2016. Sorting is one of the most important steps in plastic recycling, and these codes make it easier to tell plastics apart. Let us look at each code.
What the Recycling Symbol Means
The recycling symbol for plastics is a triangle with a number inside it. The triangle itself is made of three arrows. Below we explain the triangle and the numbers separately.
What Does the Recycling Triangle Stand For?
The recycling triangle is made of three arrows that follow each other around a Möbius loop. The first arrow stands for collecting, sorting and separating.
The numbers in the triangle, explained below, make this sorting step easier. The second arrow stands for making new goods, containers and other products from recycled plastic, and the last arrow stands for using those recycled products.
What Do the Numbers in the Recycling Symbol Mean?
1. Polyethylene Terephthalate (PETE)
Number 1 in the recycling triangle shows that the plastic is polyethylene terephthalate. It is widely used for drink and food containers and for fibres, and it is easy to recycle.
2. High-Density Polyethylene (HDPE)
Number 2 shows that the plastic is high-density polyethylene. It is used for all kinds of packaging containers, pipes, toys, wire insulation and many light household items, and it is one of the most important materials in the plastic packaging industry. HDPE can be turned into packaging containers by injection molding, blow molding and injection blow molding.
3. Polyvinyl Chloride (PVC or V)
This plastic, identified by number 3, was once so widely used that it competed with polyethylene for first place. Its use fell sharply after it was found to have caused cancer and deaths among workers who handled it. Although production was changed and the residual vinyl chloride monomer responsible for the cancers was cut to 5 ppm, the market never fully recovered. PVC is still used for bottles, wires and cables, window frames and other products.
4. Low-Density Polyethylene (LDPE)
Number 4 inside the triangle identifies low-density polyethylene. LDPE is used for packaging, toys, adhesive tape, all kinds of plastic bags and many other products.
5. Polypropylene (PP)
Number 5 stands for polypropylene, the third most used polymer in the world. It is used for disposable containers, household goods and car parts, as well as woven sacks, sports equipment and much more. Polypropylene is also sold under trade names such as Moplen and Hostalen PP.
6. Polystyrene (PS)
The fourth most used polymer in the world is identified by number 6 in the recycling triangle. This clear, easily shaped material is also a very good insulator and is used for household and electrical appliances, car parts and many other goods, as well as lightweight structures, decorations and crafts. It is not considered safe in contact with food. For more on plastics and health, read our article on the microplastics crisis.
7. Other Plastics
Code 7 covers all other plastics. Plastic items can be made from blends of different plastics or from special plastics, and recycling them can be very difficult and may need special equipment. Even so, taking plastics to a recycling centre is one of the ways we can reduce plastic waste and protect the environment.
Things to Keep in Mind When Recycling Plastic:
1. Recycled plastics must be separated by raw material.
2. After separating them by raw material, scrap plastics should also be sorted by colour.
3. Recycled plastic must be completely dry and clean, even after shredding.
4. Recycled plastic should not be stored for long, because its properties degrade, and it should be kept in suitable conditions.
5. Additives that suit the plastic in question should be used.
Further reading: What is plastic waste and how is it managed?
