Extensional flow of polymer melts play a dominant role in polymer processes such as film blowing

fiber spinning and thermoforming. Knowing the extensional flow properties of the polymer melts is very important to control and predict their ability to be shaped or processed into products. In many cases and compared to shear flow

transient extensional viscosity is more sensitive for characterizing polymer structures such as macromolecular structure

anisotropy of particles filling and phase morphology of polymer blends. In this paper

the extensional rheometers or fixtures commonly used and their principles are briefly introduced. Moreover

some recent investigations about the extensional flow properties of pure polymers

polymer nanocomposites and polymer blends are reviewed and discussed.