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Interfacial Dilational Rheology with PAT1M and PAT2P

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.  

A typical dilational experiment can be carried out with our automatic drop shape tensiometers PAT. Using the dosing system the drop area can be subjected to transient or harmonic perturbations:

Both instruments, PAT1M and PAT2S provide the opportunity to change the size of a drop or bubbles according to a given time line. This can include harmonic perturbations and various types of transient area changes, such as ramps, jumps, and combinations of them. For harmonic perturbations, frequencies are rather limited, as at too high frequencies the drop profiles deviate from a Laplacian shape and therefore the main condition of the methodology is no longer fulfilled. A clear indication for being beyond the physical limit in an oscillation experiment is the standard deviation as measure for the quality of fitting the experimental drop profile. As soon as these values of the standard deviation become much larger than those observed at
constant drop size the chosen frequency is out of the acceptable limits.
SINTERFACE Technologies e.K
M├╝ggelseedamm 70
12587 Berlin

+49 (0)30 23544406
+49 (0)30 23535716

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