Petroleum Jelly or "petrolatum" is used as a skin protectant, such as for soothing chapped lips, for example. It is also sometimes used as a base material for pharmaceutical creams or ointments.
* While a particular model/version may be used as an example in this method, any current or past model/version from the same series may also be used. Please consult a sales associate to discuss the most current instrumentation and software available.
The test is run at room temperature.
Various manufacturers use equipment ranging from the Brookfield RVT Dial Reading Viscometer to Brookfield Digital Viscometers or Rheometers. They typically use their own proprietary choice of T-bar spindle and speed as well. Several readings are made as the spindle travels down [and back up] through the sample. The data are taken at regular intervals such as 30 seconds, for example, and an average value calculated for a QC/QA measure. However, automated data acquisition may be performed with the Brookfield RVDV-III Ultra Rheometer and Rheocalc software, for example.
A commercial product was tested using a Brookfield RVDV-III Ultra Rheometer and the method listed above. Typical automated-test data comparing two different products are shown below:
Click to enlarge
The above graph was custom-sized, using the new "Custom" window feature available in Rheocalc32 Version 3.0. This software version was released during February, 2006. Note that both the title and subtitle lines were created with user-selected fonts, font sizes and styles. Furthermore, the graph's data points [and traces connecting the points] were customized - different shapes and colors were used, with user-selected point sizes, as well.
The data used for averaging in the experiment above are selected from the "middle region" - that is, 50 to 250 seconds. This corresponds to the spindle traveling through the bulk of the sample. The spindle enters the sample from° to 50 seconds, causing the measured torque and corresponding viscosity to increase from zero. Conversely, the spindle exits the sample from 250 to 300 seconds, causing the measured torque and corresponding viscosity to decrease to zero. Most of the data points during 50-250 seconds lie between 1,250,000 and 2,500,000 cP in this particular case.