How are plastic bottles made?

Find out with Sir Sidney McSprocket!

Sir Sidney McSprocket’s been in action capturing facts – all about manufacturing!

Today he’s finding out all about plastic bottles!

A plastic bottle is a common enough item and one with which you’ll be well acquainted!

But how is a plastic bottle made?

Many plastic bottles are made of a substance called PET – that’s short for polyethylene terephthalate. It makes bottles that are lightweight and strong – useful when bottles are used for food and drinks.

Pellets of PET and recycled plastics are loaded into special ovens and heated to 260 degrees centigrade so that it melts.

This melted plastic is then injected into small moulds – that’s like a hollow space that shapes the plastic into long thin tubes.

The tubes are then re-heated and placed in bottle shaped moulds – where high pressured air inflates them to fill the mould and to take their final shape.

Sometimes, to make sure that the bottom of each bottle has a flat shape to help it stand up straight, another piece plastic is joined to the bottle during the moulding process.

The bottles must be cooled instantly or they will lose their shape as the warm plastic will creep downwards.

Sometimes cold water or liquid nitrogen might be circulated around the moulds, or air is blown at room temperature.

Like most manufacturing, it’s important to test samples from the production line.

Samples will be measured to make sure they’re the right shape and size. They’ll also be squashed to see how strong they are. Once ready, the finished bottles will be boxed up, ready for dispatch.

The final step is putting a cap onto the bottle. This is done by the food company, after the drink or food has been added.

Whilst plastic is a very versatile material, it can take hundreds of years to decompose naturally. That’s why it’s really important to recycle any that you use!

Sidney McSprocket is Fun Kids’ resident inventor!

When he’s not in Edinburgh, tinkering with wacky contraptions in his workshop, he’s finding out all about manufacturing!

In the latest series, Sidney is finding out about a whole load of everyday objects from tin cans and toothbrushes to plastic bottles and Pyrex…

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Sidney McSprocket’s How’s it Made, with support from the Royal Commission for the Exhibition 1851.

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