Various materials such as epoxies or other composite resins, slow curing adhesives, gelatins, hydrocarbon gels.
* 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 Cure Mode algorithm was developed in response to customer concerns that (1) their gel timers did not provide them with any viscosity or rheological data, and (2) they could not afford expensive rheometers that would monitor gelation or "curing" of materials such as epoxies, for example. This algorithm allows data to be taken over very large viscosity ranges - several decades, in fact. Brookfield Rheocalc32™ software (Version 3.0 or higher) is used for instrument control and data acquisition, with DV-II+ Pro Viscometer, DV-III+/DV-III Ultra Rheometer, for example. The software "wizard" in Rheocalc is used - "Cure Mode" is selected, and the wizard guides the user in setting up a test.
In the following example, Brookfield LVDV-III+ was used with SC4-27RD disposable spindles and SC4-13RD disposable sample chambers. The initial speed was 100 rpm. The viscosity increased as the epoxy system reacted or cured. Each time the measured torque reached 90% of Full Scale Range or "FSR", the speed was decreased by a factor of 10. Rheocalc32™ version 3.0 software was used. The program ended the run when 90% of FSR was reached at the slowest speed - in this case,°.01 rpm.
Figure 1: Expoxy Cure at 23C:
Each curve represents a test at a different rotational speed for the spindle. The left-most curve is the torque data at 100 rpm; the right-most curve is the torque data at°.01 rpm. The measured torque increases at each given speed, as the cure proceeds.
Figure 2: Spindle Speed vs. Time Data for the Expoxy Cure Test:
Speed is decreased each time the measured torque reaches 90% of Full Scale Range or "FSR", during the epoxy cure at 23°C. The speed intervals shown in the graph correspond with the torque data in Figure 1.
Figure 3: Viscosity vs. Time Data for Epoxy Cure Test at Three Different Temperatures Epoxy Cure Monitored at 23, 50 and 60 °C.:
The reaction or "cure" proceeds faster as the temperature is increased. Note that the initial viscosity is lower at the higher temperatures.