Brookfield Engineering

Toothpaste

Laboratory Viscometer Application Data Sheet

USE

To aid in the prevention of tooth decay, and protect teeth and roots against cavities.

YIELD STRESS TEST

Test Equipment:

  • Instrument: YR-1 Rheometer
  • Spring Torque Range: RV
  • Spindle: Vane Spindle V-74; Immerse to the Primary Immersion Mark
  • Speed, rpm: 1.0 rpm
  • Temperature: Room Temperature (70-72°F).

We used the Brookfield RVYR-1 Rheometer, with EZ-YieldTM v1.4 software for automated instrument control and data acquisition. The YR-1 performs yield stress tests, which determine the stress that must be applied to make a material flow. The corresponding apparent yield strain is the deformation at which the sample structure breaks down - and at which the sample flows. The product was squeezed out of the tube into a 50 mL beaker, where it was tested. The spindle was immersed in a fresh part of the sample for each trial. The spindle was cleaned before each trial. Representative data from the analyses are shown in Figure 1, below:


Figure 1: Toothpastes A and B at Room Temperature (70-72°F).

Figure 1 demonstrates Stress (Pa) vs. Apparent Strain (rad) of Toothpastes A and B at 1 rpm. Testing with the RVYR-I and the V-74 vane spindle at 1 rpm produced on-scale results. The stiffness or firmness of the material is reflected in the slope or steepness of the stress-strain curve. The yield stress is the maximum stress, in each run. Toothpaste A's yield stress (229 Pa) was significantly higher than toothpaste B's yield stress (119 Pa). This translates into Toothpaste A being able to keep its structure while under more stress than Toothpaste B. The results were repeatable.