These devices feature a glass or steel capillary of exact inner diameter and length. Capillary viscometers utilizing gas pressure Typical applications are highly viscous substances, such as polymer melts, and also PVC plastisols, greases, sealants, adhesives, and ceramic masses.
However, the weight is replaced by a driving motor, which realizes high shear stress values (up to 900 kPa) and medium to high shear rates (around 1,500 s -1). Such a viscometer works in the same way as a weight-driven instrument (see the above section). High-pressure capillary viscometers with electric drive In such devices, the polymer sample is exposed to medium shear stresses (from 3 kPa to 200 kPa) and medium shear rates (from 2 s -1 to 200 s -1). ISO 1133 states the dimensions of cylinder, piston, and die as well as the approved weight pieces. capillary) at the bottom of the cylinder. The sample then has to pass through an extrusion die (i.e. The steel piston glides down inside a vertical steel cylinder, which contains the sample. Ī defined weight on top of a piston is pulled down by gravity. Consequently, such an instrument is also named MFR or MVR tester. These parameters help to assess the quality of the melt and to predict its behavior when processing it. The device returns the MFR (melt mass flow rate) in or the MVR (melt volume flow rate) in. This type of instrument plays a major role in checking polymer melts.
