1. Overview
TA Instruments AR-G2 Magnetic Bearing Rheometer is a high-sensitivity research rheometer designed for advanced characterization of complex fluids, polymer melts and solutions, suspensions, emulsions, gels, and soft solids. Its defining feature is the ultra-low-friction magnetic bearing system, which provides exceptional torque sensitivity, enabling measurements at extremely low shear stresses and low viscosities.
Typical capabilities include
- Steady shear viscosity and flow behavior
- Oscillatory viscoelastic measurements
- Stress-controlled and strain-controlled operation
- Ultra-low torque response for fragile or low-viscosity samples
- Full environmental and temperature control with multiple geometries
Capabilities:
Viscosity flow curve, shear stress, strain, phase angle, storage and loss modulus
Viscoelasticity, yield stress, creep compliance and stress relaxation behavior
Environment Test Chamber (ETS) with liquid nitrogen cooling source
Features:
- Torque range: 0.01 uN.m to 200 mN.m
Frequency range: 10 -7 to 100 Hz - Temperature range: 160 to 600°C
Maximum heating rate: 40°C/min
Maximum cooling rate: 40°C/min
2. Principle
The AR-G2 measures rheological behavior by applying stress or strain and recording the corresponding deformation or torque response.
The magnetic bearing system suspends the motor shaft without mechanical contact, minimizing friction and enabling accurate low-torque operation.
Core measurement functions include
- Shear viscosity: relationship between shear rate and flow resistance
- Elastic modulus G′ and viscous modulus G″: from oscillatory testing
- Phase angle and damping: viscoelastic balance
- Yield stress: flow initiation threshold
3. Data Interpretation
- Flow curves: viscosity versus shear rate indicating Newtonian, shear-thinning, or shear-thickening behavior
- Amplitude sweeps: defining the linear viscoelastic range
- Frequency sweeps: G′ and G″ dependence on time scale or relaxation
- Temperature ramps: transitions such as gelation, melting, network breakdown
- Creep and recovery tests: structural resilience and long-time deformation
- Yield stress metrics: determining flow onset
Interpretation notes
- G′ higher than G″ indicates more elastic or solid-like response
- G″ higher than G′ indicates viscous or liquid-like flow
- G′–G″ crossovers often correspond to gel points or structural transitions
- Sensitive torque control allows evaluation of weak networks, dilute solutions, and low-viscosity fluids
4. Example Applications
- Polymer melts and concentrated solutions: viscoelasticity and temperature dependence
- Dilute or low-viscosity systems: surfactants, micellar fluids, solvent-rich polymers
- Gels and hydrogels: gelation kinetics, strength, relaxation
- Suspensions and colloids: stability, particle interactions, yielding
- Food and cosmetic formulations: texture, spreadability, flow initiation
- Emulsions and creams: droplet stability and viscoelastic structure
- Inks, coatings, and paints: shear-thinning and processing behavior
Publications involving the system
Microstructure and Viscoelasticity of Oppositely Charged Ionomer Blend Melts,
Macromolecules 2025, https://doi.org/10.1021/acs.macromol.4c02781