Viscosity is a measure of a medium’s internal resistance to flow. A higher viscosity indicates that the medium is thick flowing – a lower viscosity that it is thin flowing. The term viscosity derives from the typically thick flowing berry juice of the mistletoe plant species (viscum). Birdlime was made from these mistletoes, and “viscous” denotes “thick as birdlime”.
Unit of measurement: Pa s or mPa s
BOCHEM offers 2 different digital stirrers, who can stirr media from low until high viscosity:
RS 9000 und RS 9001,
sowie 12 different stirrer blades with different diameter, shaft lenths fom 300-800 mm and 3 different shaft diameters from 7, 8 and 10 mm.
Our stirrer blades are threaded, though you are very flexible with your equipment!
Have a look at the stirrer range:
(1) Unless otherwise noted, the values refer to the viscosity at 20 ° C.
1 mPa = 0,001 N/m² = 10-7 N/cm²
(2) There is a very wide range of viscosities in polymers, which essentially depends on the chain length and its branching structure (and of course on the temperature). For example, silicone oils (PDMS) are manufactured with defined viscosities between 0.6 mPas at 25 ° C and 1,000,000 mPas at 27 ° C. However, polymer melts can also have much higher viscosities. In the case of a UHMW-HDPE (for hip joint implants), viscosities beyond 1013 mPa · s at 150 ° C. were measured.
However, one must consider that with normal unfilled polymer melts at the latest from a viscosity of 10,000 mPas structural viscosity occurs, the intensity of which (i.e. how much the viscosity drops at high shear rate) increases with increasing viscosity.
(3) In principle, the viscosity of a crystalline solid is infinite. Since irreversible deformation can still occur in the long term due to the unavoidable defects in the crystallite, one obtains very large but finite values with real crystalline substances.