Thermosetting plastics are very hard and brittle at room temperature. At high temperatures the plastic does not become soft and keeps its shape. It does not begin to decompose until reaching approximately 200 °C / 392 °F.
The high degree of cross-linking is called “hardening”. Thermosetting plastics are also called “duroplastics”. Thermosetting plastics are non-plastic deformable, non-meltable and non-weldable. They are insoluble and only slightly swellable.