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Identification and code of plastics

The existence of many types of plastics and polymers on the market and their recyclability led to the creation of identification codes, the symbol for which dates back to 1970. This first identification document was created by a group of students participating in a Container Corporation of America competition. The symbol reflects the recycling process: from the collection of the material, to the recycling process, to the purchase of the recycled products.

Plastic identification codes as such, however, came years later from the American Society of the Plastics Industry. They originated in 1988 with the aim of facilitating the identification of each type of plastic and to be able to separate them properly, making a correct management of these.

For this classification of plastics, a triangle with three successive arrows surrounding a number from 1 to 7 is used as a symbol. This triangle is known as the Möbius triangle, the universal symbol of recycling, and identifies the material from which the product is made, as well as the possibility of being recycled.

Classification of plastics codes

Number 1: PET (Polyethylene terephthalate)

PET is one of the most widely used plastics in food packaging, thanks to properties such as its low production cost, its light weight and, above all, its great recyclability.

Number 2: HDPE (High Density Polyethylene)

This identification code is used to classify plastics that are resistant to chemicals, not very flexible, but easy to manufacture and handle, such as HDPE plastic. The most common applications for this plastic are grocery bags, packaging for cleaning products, personal care products and others. As soon as it is recycled, it can be used again for the same purpose it had at the beginning of its useful life.

Number 3: PVC (Polyvinyl Chloride)

This plastic identification number corresponds to materials that are characterised by chlorine in their composition, which makes them difficult to recycle, such as PVC. They are also characterised by their high acid resistance and their hardness, which makes them ideal for tubes, pipes, medical equipment and much more.

Number 4: LDPE (Low Density Polyethylene)

Low Density Polyethylene or LDPE is identified by the number 4, and is used to designate those plastics that are very flexible and have great sealing properties, which is why it is usually found in the food industry. It is also commonly found in the form of bags, laboratory containers or frozen food. After recycling, it can be reused for containers, litter bins, panels and pipes.

Number 5: PP (Polypropylene)

Polypropylene is the ideal material for microwaveable packaging, as its main characteristics are hardness, vapour barrier and heat resistance. This makes it perfect for food packaging that is sterilised. It is also commonly found in sauce pots, lids and medical and veterinary packaging. Once it has passed the recycling process, it is generally used to make brushes, trays or illuminated signs.

Number 6: PS (Polystyrene)

PS plastic or polystyrene is a plastic that is mainly used in food trays, in the dairy industry, for household appliance packaging and also to make cups for hot drinks. It is also a material that can be recycled an infinite number of times, giving it a very long life span. However, it does have one negative quality, and that is that at temperatures above 80°C it releases styrenes. Styrene is considered carcinogenic by the Environmental Protection Agency and the International Agency for Research on Cancer.

Number 7: Mixed plastics

This code includes a wide range of plastics that are very difficult to recycle. Most articles classified under this number include several different types of plastics in their composition. Typically, mixed plastics are found in sunglasses, but also in some water bottles or food packaging.

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