Paper Number
AR12 

Session
Applied Rheology for Pharmaceuticals, Food, and Consumer Products

Title
A new pressurized Couette cell for rheological characterization

Presentation Date and Time
October 24, 2019 (Thursday) 10:50

Track / Room
Track 6 / Room 306B

Authors (Click on name to view author profile)

1. Ahuja, Amit (TA Instruments)
2. Lee, Reginald (TA Instruments)
3. Latshaw, Alina (TA Instruments)
4. Nowak, Maik (BASF SE)
5. Foster, Peter (TA Instruments)

Author and Affiliation Lines (in printed abstract book)
Amit Ahuja¹, Reginald Lee¹, Alina Latshaw¹, Maik Nowak², and Peter Foster^1
1TA Instruments, New Castle, DE 19720; ²BASF SE, Ludwigshafen am Rhei, Germany

Speaker / Presenter 
Ahuja, Amit

Text of Abstract
Despite the relevance of pressure in several industrial processes, the impact of pressure on the rheological properties has been less explored in comparison to the effects of temperature. This is mostly due to the challenges to develop a high sensitivity pressurized rheological geometry. The contributions from mechanical bearings and high-pressure mechanical seals can severely limit the sensitivity of the measurements, particularly for low torque measurements. The inherent baseline friction from a conventional mechanical bearing can be as large which typically restrict low torque measurements to 100 µN.m. Using a Couette geometry which utilizes a novel design (patent pending) to provide material pressurization (up to 5 bar) without conventional bearings and mechanical seals improved low torque sensitivity (1 µN.m in oscillatory and 10 µN.m in shear flows). This pressure cell allows testing in both steady shear and dynamic oscillatory flow modes over a range of testing conditions (-5°C to 150°C) simulating extreme processing, usage, and storage conditions, to characterize shear and viscoelastic properties for a variety of materials ranging from low viscosity to structured complex fluids. First, the novel design features of this pressure cell will be discussed which will be followed by examples involving two potential applications. Particularly, in the food industry, most food products undergo extreme processing conditions of high temperature and pressure and the measurements of sample behavior above 100°C is extremely difficult due to water-based formulations. By using Xanthan gum solution in water as a model system, it will be demonstrated that testing in this pressurized Couette cell suppresses boiling of the volatile components from the formulation, allowing to characterize the structure of the sample in the right processing conditions. The second example utilizes a commercial shaving foam from a pressurized container and discusses the stability and pressure-induced changes on the foam rheology.