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Easy Rheometry Practice with Household Materials

February 23, 2018

Whether you are looking to learn rheometer instrumentation or train a new rheometer user, practicing sample loading and testing is very helpful.  Conducting rheometry measurements on common products is an easy way to train while allowing for blunders without much consequence. The more experience you gain with loading samples and adjusting test settings, the more intuitive it will be for you to optimize measurements for your industrial products.

 

 

Avoid using expensive samples to allow new users more freedom to make mistakes and learn how to load a sample without handling toxic chemicals. Practicing with liquid soaps, vegetable oil, and fruit juices is a good way to get a feel for the differences between loading sample in various measuring systems. This exercise can also help with perceiving which consistencies can be loaded with a plate and which require a cup.  Additionally, the impact of bubbles on the rheological properties can also be taught through measuring shampoo in its un-lathered state (with few bubbles) and compared to the results on the same shampoo when it is lathered into a foam.

 

Along with sample handling, running practice measurements will encourage users to take into consideration temperature equilibration and the potential for evaporation during the test. Five minutes more may or may not be sufficient to raise the sample temperature to match the rheometer temperature. Challenge the users to guess temperature equilibration time settings for a sample, look at the data, and then ask them to run a fresh sample but with a temperature equilibration time double of the original time. The difference in data quality may astonish them. Furthermore, observations of film formation on the parts of the sample exposed to air can help demonstrate how evaporation impacts the data. Tests conducted with and without use of a solvent trap can help reinforce the idea that rheometer users need to account for evaporation in the sample during measurement.

 

 

Another aspect of rheometry practice is adjusting the time per data point to be appropriate for the sample. Often colloidal samples or samples with many different chemical components require longer data averaging to account for the various motions between the constituents. Contrastingly, simple structures or less-structured materials do not need as much time per data point to capture their response to the applied shear. New rheometer users often do not consider this characteristic. For any viscoelastic sample, ask the trainees to run a flow curve with only 0.5 seconds per point, and then to use a fresh sample while running the flow curve at 5 seconds per point. This exercise will establish the importance of data collection settings through observing the resulting differences in the data.

 

Being comfortable with using the rheometer is important for producing accurate data while conserving time and resources.  

 

Download our free guide for practicing rheometry with household products.  

 

For more ideas on how to train new rheometer users, contact us for a free consultation. We also offer an assortment of rheology training modules both online and in-person for all levels.      

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