These are the polymers that can be moulded only once. They can not be softened by heating and their shape can not be changed. These are called Thermosetting plastic.
The monomers are attached in a three dimensional arrangement in these kind of polymers .
Their examples are malamine and Bakelite.
Malamine is used in the production of unbreakable utensils.
Bakelite is used in the handles of pressure cookers and other handles that are attached to hot surfaces.