Rheologic Properties: Selecting Measurement Tool (Viscometer)

Rheologic Properties: Selecting  Measurement Tool (Viscometer)

Introduction:

Assessment of rheologic properties is critical to a number of industries including manufacturing, pharmaceuticals and food processing. In order to accurately measure the behavior of substances in different environmental conditions, rheology tools that are precise enough have to be used. This article explores why one should choose the right measuring instrument and what implications this has for substance behaviour on measurement accuracy.

Significance of Choosing the Right Measurement Tool:

The choice of an appropriate measuring device is crucial in determining how a particular substance flows. This selection depends on various parameters such as nature of the material and conditions under which it will be examined. For example, materials where shear rate is linearly related to applied force requires constant shear instruments.

Constant Shear Instruments:

These devices help generate data points on flow behavior graphs for substances. By extending a line from these points back to the zero interceptor for flow, investigators get a complete picture concerning material response under stress. However, this approach supposes that the substance to be tested behaves like water and obeys Newtonian physics.

Difficulties with Non-Newtonian Substances:

Nevertheless, not all substances behave as a Newtonian fluid. The non-Newtonian substances vary in flow characteristics under different conditions rendering single-point measurement instruments to be ineffective while measuring them. These devices fail because they do not allow for variation of speed in measurements hence, without the possibility of measuring over different speeds, these instruments are inadequate to describe completely behavior of a substance.

Multi-Point Instruments for Non-Newtonian Substances:

To overcome such complications with non-Newtonian substances there is need for multi-point type of instruments. Such equipment can measure viscosity at various velocities providing wider understanding on how it changes across varying circumstances. This moves from static states to dynamic processes like stirring, pouring or spreading that multipoint instruments give complete data on which single-point ones are unable to collect entirely.

Understanding Substance Behavior:

The behavior of substances varies significantly based on their rheologic properties. Newtonian substances maintain a constant viscosity regardless of the applied force, simplifying measurement procedures. In contrast, non-Newtonian substances exhibit diverse behaviors such as shear-thinning, shear-thickening, or viscoelasticity, necessitating advanced measurement techniques.

Shear-Thinning Substances:

Shear-thinning substances, also known as pseudoplastic fluids, exhibit a decrease in viscosity as the shear rate increases. Common examples include paints, ketchup, and certain types of polymers. To accurately assess the flow behavior of shear-thinning substances, multipoint instruments are indispensable, as they can capture the viscosity changes across different shear rates.

Shear-Thickening Substances:

Conversely, shear-thickening substances experience an increase in viscosity with higher shear rates. These substances, also referred to as dilatant fluids, defy the linear relationship between shear rate and viscosity observed in Newtonian fluids. Examples of shear-thickening substances include cornstarch suspensions and certain types of clay slurries.

Viscoelastic Substances:

Viscoelastic substances possess both viscous and elastic properties, exhibiting behaviors such as creep, stress relaxation, and hysteresis. Common examples include rubber, polymer melts, and biological tissues. Characterizing the rheologic properties of viscoelastic substances requires sophisticated measurement techniques capable of capturing their complex behavior accurately.

Conclusion:

In conclusion, the determination of rheologic properties is essential for understanding how substances flow and deform under various conditions. Selecting the appropriate measurement tool is paramount, especially when dealing with non-Newtonian substances that exhibit diverse flow behaviors. While single-point instruments suffice for Newtonian fluids, multipoint instruments are indispensable for accurately characterizing the rheologic properties of non-Newtonian substances. By employing advanced measurement techniques, researchers can gain valuable insights into substance behavior, facilitating advancements in numerous industries.