It is very common to hear the term capillary rheometer instead of viscometer, but both terms used to describe a testing instrument that measures the viscosity of the material. This is done through timing material moving through a small capillary of known diameter.
The benefits of this process are that the viscosity of materials, particularly non-Newtonian fluids, cannot be measured using other types of systems because of the change or variance in the flow under different conditions. With the use of a capillary viscometer, the conditions can be carefully controlled for the temperature to provide a consistent way to test.
The Importance of Viscosity
It is essential to understand the viscosity of the material to understand the way it will behave under different environmental factors. This includes thermoset plastics, polymers as well as elastomers. How these materials resist flowing, the viscosity will ensure that specific materials are suitable to different conditions.
How They Work
To use a capillary viscometer, a small sample is prepared and placed in the chamber to allow to come to the desired temperature. Once the correct temperature is reached for the test, the sample is drawn into the testing barrel and allowed to flow naturally through the capillary to a lower chamber.
The time that the sample requires to move through the capillary is measured. This time is then converted to determine the viscosity of the sample at that temperature. The faster the material travels through the capillary, the lower the rate of viscosity as there is less resistance to flow.
There are different sizes and options in capillary viscometer or capillary rheometers on the market. Smaller systems are very effective when there are limited samples to run while the more advanced systems provide continual processing, some even come with extruders to supply the test barrel and limit the need for operator handling of the test equipment.
