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Pour water and then honey into a bowl, and you’ll have a pretty good idea of which one is more viscous. But to put a number on that, it takes a viscometer or rheometer. Here are a few things to know when shopping for such an instrument.
The U.K.’s Royal Society of Chemistry defines viscometry as: “The measurement of the viscosity of fluids by observing the relative motion of the fluid and an object.” It adds: “Viscometry is used to measure the molecular weight of polymers.”
To get a handle on rheometry, watch this introduction to rheology. This video defines rheology as: “The study of a material’s flow behavior under applied deformation forces.”
At Labcompare’s rheometers/viscometers page, scientists can explore a wide range of products in this market segment. In most fields that study the flow of materials—from making chemicals and cosmetics to testing foods and beverages and petroleum—scientists and engineers require a viscometer or rheometer.
These platforms come in a wide range of options, and here are a few.
Touch and timing
When asked about the latest advance in a rheometer or viscometer from AMETEK Brookfield (Middleboro, MA), Robert McGregor, former director, High End Instrument Sales, points to the touchscreen displays. These can be used “to rapidly set up tests and capture real-time viscosity data for analysis,” he says. Examples include the new DV2T Gel Timer and DV3T Gel Timer instruments. “The DV3T Gel Timer displays the viscosity flow curve versus time and clearly indicates the sudden rapid rise in viscosity to indicate that gel time for the resin or gel coat material under test has been achieved,” McGregor explains. “This visual confirmation of change in viscosity gives users of thermoset materials the confirmation they require on working time to get their plastic material to completely fill a mold—for example, turbine blade, bathtub, auto component made of plastic, etcetera.”
In addition, McGregor notes that existing viscometers and rheometers can be retrofitted with Brookfield’s special magnetic coupling. This “secures the standard glass rod used by the gel coat and resins industry to measure gel time,” McGregor says. “The coupling provides lab technicians with an affordable mechanism—less than $300—that not only secures the glass rod, but also disconnects quickly at end of test so that it can be quickly pulled out of the test material before the material hardens completely.”
But, there’s still another reason to consider this retrofit. This new approach to measuring gel time provides “the ability to specify a viscosity value that can be associated with gel time,” McGregor notes. “It makes the test method more scientific in nature.”
According to McGregor, major manufacturers of thermoset materials are adopting the Brookfield solution and equipping their labs with AMETEK Brookfield’s Gel Timer instruments.
Raising the bar at Anton Paar
From Anton Paar USA (Ashland, VA), lead scientist Abhishek Shetty talks about some new platforms, including the ViscoQC 100 and 300 viscometer. Shetty says that these “viscometers represent a significant advancement in the reduction of human error in viscosity measurement.” Some of the features that support that claim include automatic spindle recognition with Toolmaster, automatic guard detection with TruGuard, automatic speed function with TruMode, automatic bearing check with TruSine, and reproducible results with digital leveling.
“The ViscoQC 100 allows you to make the most consistent and reliable measurements using a single-point rotational viscometer,” Shetty says. “It is easy to use, easy to transport, and features a remarkably small footprint.” He notes that the ViscoQC 300 offers the same benefits, plus 21 CFR Part 11 compliance and the ability to test a larger range of speeds.
Anton Paar also developed the MCR 702 MultiDrive rheometer. Shetty points out several key features: “Magnetic Suspension Linear Drive for drift-free testing,” the “IsoLign Piezo Flange for unsurpassed gap setting and compensation during testing,” and the “Optoelectronic Technology for contact-free temperature and precise temperature measurements integrate the moving measuring systems.”
For dynamic mechanical analysis (DMA), Shetty emphasizes even more features of the MCR 702 MultiDrive rheometer. “Simple, self-aligning lower drive motors—Linear Drive and Rotational—offer duality not found in any other mechanical testing devices,” he says. “The MCR 702 MultiDrive is a full-fledged rheometer when the lower rotational drive motor is utilized, and transforms to a premier, full-range DMA when the lower linear drive is utilized.”
Do it dynamically
U.K.-based Malvern Panalytical offers a wide range of devices for measuring viscosity. Some of them rely on rotation. One example is the Kinexus DSR. The company says that this dynamic-shear rheometer is “designed for routine analysis and QC testing in the asphalt industry, with true ‘plug and play’ functionality for all measuring systems and environmental control units.” In addition, this platform “enables pioneering Standard Operating Procedure (SOP)-based testing with a built-in library of standard test protocols for asphalt and access to standard rheological test modes,” according to Malvern Panalytical.
Many other companies also offer rotation-based viscometers. For example, BYK-Gardner (Columbia, MD) offers a collection of rotational viscometers. The company describes its byko-visc DS as “an easy-to-use digital Stormer viscometer that measures in KU (Krebs units), grams, and centipoise units.” For quality control and research and development, BYK-Gardner recommends the byko-visc Advanced. With the byko-visc Premium, users get what the company describes as “the latest features in programming and communication technology.” That includes WiFi, Bluetooth, and USB interfaces.
Take it with you
To make viscosity measurements where needed, a portable device can be useful. There are plenty to consider at Labcompare’s portable viscometer webpage.
For example, FungiLab (Barcelona, Spain) makes glass capillary viscometers and, as the company points out, “We can also manufacture glass capillary viscometers with customer-specified constants.”
AMETEK Brookfield makes a variety of viscometers that can be taken where they’re needed. Plus, these devices represent a range of measurement methods, including falling ball, in tank, and spindle.
Viscosity impacts the production of many items, including turbine blades. (Image courtesy of the U.S. Department of Energy.)Does your material go with the flow? Find out with a viscometer or rheometer.
Mike May is a freelance writer and editor living in Texas. He can be reached at [email protected]