Method of measuring extensional viscosity of polymer melts and capillary injection system

A capillary injection system for measuring an extensional viscosity of a polymer melt, comprising:

• a barrel, having a cavity configured to contain the polymer melt;
• a capillary, coupled to the barrel;
• a piston, coupled to the barrel, configured to provide a force to the polymer melt to make the polymer melt flow through the capillary;
• a first pressure transducer, configured to measure a first pressure of the polymer melt at an inlet of the capillary;
• a second pressure transducer, configured to measure a second pressure of the polymer melt at an outlet of the capillary;
• and
• a rheometer, configured to:
• based on a weighted generalized Newtonian fluid (GNF) viscosity model, obtain a viscosity profile of the polymer melt according to a transport equation, a Navier Stokes equation, and a Trouton function;
• obtain a general viscosity of the polymer melt from the viscosity profile according to the first pressure and the second pressure, wherein the general viscosity comprises a shear viscosity of the polymer melt and the extensional viscosity of the polymer melt;
• and
• extract the extensional viscosity from the general viscosity.