A number is printed under each plastic bottle, checking it is essential, here’s why

Several times we have discussed the issue of the large quantity of plastic that contaminates our planet in every corner. There are numerous solutions aimed at reusing this material and cleaning up polluted environments, but none at the moment have brought about substantial changes to the tragic situation.

Think you know enough about plastic? Its main advantage is that it is light and resistant but the science hidden inside is yet to be discovered . Take a bottle of water, locate the number printed on the bottom , and start learning more about this revolutionary material.

via afamily.vn

Have you never noticed it or have you always wondered: what does that number printed on the bottom of the plastic containers mean?


There is not just one plastic but there are different types, and it is the simplicity with which it is possible to form new ones that makes this material very interesting.

Plastic is made up of very long chains of carbon atoms , to which other elements are linked: it is precisely the latter that determine the macroscopic characteristics of the material.

There are transparent, opaque, resistant and other flexible plastics, which soften with heat and others which harden, depending on the bonds established by the carbon. 

Each plastic is made up of different molecules and different types cannot be recycled together. It’s like trying to fuse paper with glass, it makes no sense!


For this reason, the number printed on the bottom of plastic containers is fundamental: it is used in collection centers to separate the different types of plastic and then proceed to the recycling phase.

Here is the list of numbers and corresponding plastics: let’s discover the characteristics of each one and the reason why it is used for that specific container.


1) PET : this is an abbreviation used to indicate polyethylene terephthalate. It is used in most disposable containers and appears as a light and flexible plastic. 

If you have a bottle with this identification number, you should not use it more than once  as it increases the risk of bacterial contamination . Furthermore, over time this type of material releases toxic components that interfere with the endocrine system. 

Washing PET requires professional tools and very aggressive chemical washes: domestic cleaning is not enough to sanitize a bottle. 

2) HDPE : identifies a plastic whose molecules have a very high density. This results in a more rigid material , generally used for soap, detergent, oil and toy containers.

Experts recommend purchasing water bottles marked with this number , they are probably the safest and the water you drink is the cleanest. 

3) PVC : its abbreviation is certainly better known than its extended name, polyvinyl chloride. All food packaging , some cooking oil bottles, children’s and animal toys are made of this material . It is not recommended to purchase products with this plastic, which is responsible for the release of dangerous chemical substances.

4) LDPE : unlike HDPE, in this plastic the carbon chains are very distant from each other and result in a flexible plastic. It is not possible to package food products due to the release of dangerous compounds. 

5) PP : the two ‘p’s stand for polypropylene, a historic material synthesized by the Italian chemist Giulio Natta . It is used for packaging more delicate foods, such as dairy products: yogurt pots are made of this resistant and lightweight plastic . It is a thermoset which means it does not melt with heat. Compared to other materials it is an effective barrier against humidity. 

6) PS : when you buy an appliance, you will certainly find polystyrene in the box that contains it. It is the material that makes up those white and light panels that protect the product from impacts. Even common plastic plates and cups are made of polystyrene . It should not be subjected to heat sources as the release of carcinogenic substances is possible.

7) Other : all other types of plastic that do not belong to the previous sections fall into this category, such as objects made up of two or more materials. Alternative plastics of non-fossil origin are also marked with the number 7. 

Now you know something more about this material: check that the plastic used is the right one by looking at the number printed on the bottom of the containers!

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