This allows the onset of molecular motion in amorphous polymers to take place at temperatures below the melting point of such crystallites. Consequently, as the molecular motion in an amorphous polymer increases, the sample passes from a glass through a rubber like state until finally it becomes molten. These transitions lead to changes in the physical properties and material application of a polymer, and it is important to examine physical changes wrought in amorphous polymer as a result of variations in the molecular motion.