Relative Viscometer

Source: Viscotek Corp.
Relative Viscometer
The relative Viscometer is ideally suited for measuring dilute polymer viscosities.
The relative Viscometer is ideally suited for measuring dilute polymer viscosities. It provides faster analysis and greater precision than is obtainable with the conventional glass tube viscometers it replaces. The principle of operation is based on measurement of pressure drops due to the continuous forced flow of solvent and sample through two stainless steel capillary tubes placed in series. The pressure drop across each capillary tube obeys Poiseuille's Law (P=nQR).

P is the pressure drop as measured by a differential pressure transducer (DPT), Q is the flow rate, R is the tube resistance, and n is the viscosity. The sample solution is loaded into the sample loop via the syringe pump and then pushed into capillary 2 when the injection valve is turned. A steady state condition is reached when the sample solution completely fills capillary 2, solvent remaining in capillary 1 at all times. The relative viscosity of the sample solution is determined simply and directly by the ratio of the pressure drops.

From the measured relative viscosity, all other solution viscosity measurements can be calculated.

The Relative Viscometer can report the following results:

  • Relative Viscosity
  • Specific Viscosity
  • Inherent Viscosity
  • Intrinsic Viscosity
  • Absolute Viscosity
  • Molecular Weight


  • Over 50% solvent savings compared to traditional methods
  • Faster analysis than conventional glass tubes
  • Yields higher accuracy and precision
  • Closed loop system provides greater operator safety
  • Various levels of automation are available

  • System Controller- a good entry level system for a tighter budget and simplified operation.
  • Autosampler- for unattended measurement of a series of samples.
  • Robotics- the relative viscometer couples seamlessly with the Zymark laboratory robot to provide complete automation, including sample weighing, solvent dispensing, dissolution, and viscosity measurement. This level of automation virtually eliminates solvent exposure and provides unbiased measurements with a consistency unattainable by human operators.

Viscotek Corp., 15600 W. Hardy Rd., Houston, TX 77060-3102. Tel: 281-4459791; Fax: 281-931-4336.

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