Cogswell Extensional Viscosity
Capillary rheology measurements are made using a zero L/D orifice die. The entrance losses are available directly from these measurements. Measurements with a 20 L/D die are also performed. The sample, dried if needed, is loaded into a preheated test barrel of a capillary rheometer. A range of flow rates is used, attempting to cover a shear rate range of 10-10,000 /s. Pressure drop across the die is measured for each flow rate, and viscosity-shear rate data are calculated. Weissenberg-Rabinowitsch corrections are performed. Using Cogswell's equations, the extensional viscosity v. extension rate is calculated.
Measurements can also be made using a load cell instead of a pressure transducer. More complex data analyses such as the Peldom scheme [R-042] are available.
- ASTM D3835
- ISO 11443
Cogswell Extensional Viscosity, Shear Viscosity v. Shear Rate. This data appears in Matereality as Capillary Viscosity.
Number of times this test is repeated: 1
0.5 kg of pellets [details]
This data is valuable to estimate elongational flow effects as an economical alternative to direct measurements of extensional viscosity.