High-speed elongation rheometer-determination of elongational viscosity

In many processes like film blowing, film casting or fiber spinning, elongational strain occurs. A well-known correlation between shear and elongation was first found by Trouton in 1906 in the low strain area regime, where the elongational viscosity is 3 times higher than the shear viscosity. For the aforementioned processes it is very important to know and understand the occurring elongational viscosities. However, for high elongation rates the elongational viscosity was not accessible with so far existing methods, examples are the extensional rheometer after Sent-manat (SER), oil bath rheometer after Meissner or tensile rheometer after Münstedt (MTR), with the limitation of elongation rates to a maximum of 10 s^-1those setups are not suitable in the range up to 100 s¹which are typical in fiber spinning. With the "Rheotens" slightly higher elongation rates can be achieved, but in comparison to the aerodynamic fiber stretching via an aspirator, it is still by far insufficient for an industrial relevant range. Therefore, for proper understanding of fiber spinning a new technique was developed.