How come the plastic of the kettle doesn’t melt?

Answer

Plastic does soften when you heat it up.

However, everything depends on which plastic you want to use, at what temperature. There are many different types of plastic, all of which have different transition temperatures, whereby they soften or even become liquid. Plastics can have very different melting or glass transition temperatures.

Example: A plastic cup that can be used in the microwave or the dishwasher typically has a melting temperature above 100°C. In this way, the cup retains its shape even if it is washed at 75°C, for example.

Typically for household things, polypropylene, abbreviated PP, is used. (You can see this on the kettle or cup. Typically there is somewhere in a circle on which plastic has been used. For example PP, HDPE, PET.) PP has a melting temperature of about 160°C, which means that you can heat it up to about 130°C without getting too soft to lose its shape. Since water boils at 100°C, there is no problem.