Forced flow-through type capillary viscometer

Capillary Viscometers sed for concentrated solutions or polymer melts and described just above, the other, described here, used for measuring dilute-solution viscosities. The most widely used of the latter types employ a glass capillary tube and means for timing the flow of a measured volume of the solution (e.g., polymer in solvent) through the tube under the force of gravity. This time is then compared with the time taken for the same volume of pure solvent, or of another liquid of known viscosity, to flow through the same capillary. Relevant tests are from ASTM (www.astm.org). See also Dilute-Solution Viscosity and Viscometer. 

Another parameter that can be related to molecular weight is the relative viscosity, defined as the ratio of the viscosity of a polymer solution rj to the viscosity of the solvent rjo (see Table 3.3). Reliable for molecular weights >10 g/mol, the viscosities can be determined by measuring flow times through capillary tubes (diameters 1 mm), usually with gravity as the driving force for the flow. Automated instrumentation is widely available. Rotational and oscillatory type viscometers are used where a uniform, well-defined, or low shear rate is required. The ratio of the two viscosities, is called the relative... 

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