Definition of viscous flow
Viscous state (English name viscous state), also known as plastic state, is a special term for polymer rheology. Its physical meaning is the mechanical state of the amorphous polymer under the action of high temperature and large external force for a long time. It is characterized by irreversible deformation that increases with time, and produces flowing mucus. Polymers such as synthetic plastic processing and spinning of synthetic fibers are all carried out in the viscous flow state of polymers.