Extrusion coating

Have you ever seen a machine that squeezes toothpaste onto your toothbrush? That's kind of like what extrusion coating is, but instead of toothpaste, it's a melted plastic that gets squeezed onto a flat surface, like a piece of paper or a metal sheet.

First, the plastic pellets get heated up until they melt into a gooey liquid. Then, a big machine called an extruder transfers the melted plastic to a special nozzle or die. This nozzle has a funny shape that looks kind of like a flat rectangular tube.

Next, the flat surface that needs to be coated moves under the nozzle. The melted plastic oozes out of the nozzle and lands on top of the surface. It's sort of like using a giant icing bag to frost a cake.

As the plastic melts onto the surface, the temperature cools down and the plastic hardens into a thin layer. Now the surface has a protective coating, plus the coating can also make the surface look shiny or bright.

Extrusion coating is used for lots of different things. It's great for making food packaging, like bags for chips or cereal boxes. It can also be used to create waterproof coatings for things that need to stay dry, like roofs or even boats!

Overall, extrusion coating is a way to add a special layer of melted plastic onto something to keep it safe and make it look pretty.