The material properties of plastics

Leon, Lina and Maria are having a party. Plastic glasses, plastic cutlery, plastic bottles, plastic crisp packets. And all in a plastic bag. Almost everything is made of plastic. Why?

Yes, right, we do use a lot of plastic. Plastic is made of oil. It’s an inexpensive raw material, which means that plastic is cheap to produce. Not only that, plastic can be shaped and coloured easily, quickly, and cheaply any way you want it. That would be much harder with say, metal or wood.

Also, plastic doesn’t react with many chemicals. That’s why we make containers for food and drink, and medicine and cleaning chemicals with plastic. Plastic is also a strong and durable material. It’s possible to carry heavy things in a plastic bag or a plastic box. Metal containers can be equally durable, but they usually weigh much more.

So, using plastic makes packaging lighter. This saves both muscle power and fuel. Some kinds of plastic can be bent without breaking, they are flexible. And plastic does not conduct electric current, it is an insulator. These properties - flexibility and insulation - make plastic useful for covering electric cables.

And we use plastic shells for electrical devices, to avoid the risk of electricity passing through the body when holding them. Plastic does not conduct heat well either, and therefore serves as handles for saucepans and frying pans, and other things that get hot. Cheap, durable, light, flexible, insulating plastic seems to be a fantastic material! But there are also problems with plastic. Unlike wood, plastic does not decompose in nature.

Plastic is not a biodegradable material. So if plastic ends up in the forest or in the sea, it can stay there for hundreds of years. However, plastic breaks up easily. It gets brittle when exposed to sunlight. And if the brittle plastic then ends up in the water and is hit by waves, it breaks down into extremely tiny pieces, ..microplastics.

The microplastics can end up in the bodies of animals, and humans. Today, we don’t know if the microplastics found in food and drinking water are dangerous. But larger pieces of plastic in the stomachs of animals can cause them to starve to death. So, plastic should not end up in nature. We need to take care of our waste plastic.

Much of it can be used to make new things: it can be recycled. The plastic that cannot be recycled can be burned to produce energy. But then we have to be sure to collect the particles and gasses released, so that they do not go into the air. Oh, the worst thing about having a party is that you have to clean up.