New Developments 1/1/17

A new generation of bubble pressure tensiometers, including BPA-2P and BPA-2S , as follow up developments of the excellent predecessors BPA-1P and BPA-1S , are available more...

New Books 1/1/17

Textbook “Dispersionseigenschaften - Stabilität, 2D-Rheologie, 3D-Rheologie“ This textbook contains the main fundamental knowledge on interfaces, colloidal systems more...

Latest events 1/1/17

2D-3D Rheology and Stability of Disperse Systems - User Workshop, May 8-10, 2017, Berlin-Schönefeld, Germany In May 2017 the 2D-3D Rheology and Stability of Disperse more...


Interfacial Rheology

When interfacial layers are deformed there are forces acting against this deformation. There are principally two forms of deformation:
- shear deformation: changing the shape of the interface at constant area
- dilational deformation: keeps the shape constant but changes the surface area.

The possibility of expanding and compressing an interfacial layer is a peculiarity different to bulk rheology, where in a first approach the incompressibility of liquids is assumed.
Interfacial Dilational Rheology

Both profile and capillary pressure analysis tensiometers are suitable also for measuring the dilational rheology by means of area perturbations. While PAT allows for low frequency oscillations up to a maximum of 0.2 Hz, the oscillating drop and bubble capillary pressure analyzer ODBA allows studies of the dilational visco-elasticity at much higher frequencies. For the water/air interface oscillation frequencies of 100 Hz and more are feasible. For water/oil interfaces, due to viscosity and inertia effects, much lower frequencies are feasible and the limits have to be determined for each pair of liquids.  
Interfacial Shear Rheology

In addition to dilational rheology, our interfacial shear rheometer ISR provides the shear rheology of interfacial layers. Due to the applied principle of a torsion wire pendulum it is very sensitive and can probe structure formation at interfaces with very low shear visco-elasticities.