| TA Instruments | Discovery HR-2 |
| Oscillation tourqe minimum | 2 nN.m |
| Steady shear torque minimum | 10 nN.m |
| Torque maximum | 200 mN.m |
| Normal force maximum | 50 N |
| Frequency range | 1e-7 – 100 Hz |
| Angular velocity | 0 – 300 rad/s |
| Strain step | 15 ms |
| Rate step | 5 ms |
The Discovery Hybrid Rheometer measures the flow and deformation of a material or the relationship between a material’s stress and deformation. Specially, it can provide information on the mechanical properties of a viscoelastic polymer or liquid sample. Experiments can determine the storage (G’) and loss (G”) modulus as well as viscosity, creep, and stress relaxation data.
Shear modulus (G) – material stiffness; modulus = Stress / Strain
Storage modulus (G’) – material’s ability to store deformation energy elastically
Loss modulus (G”) – deformation energy losses from internal friction when flowing
Loss tangent (tanδ) – damping or index of viscoelasticity
Stress (σ) – measure of force as applied to an area (Force / Area)
Strain (γ) – deformation of the material (change in material dimensions / original dimensions)
Viscosity (η) – deformation resistance as a function of shear rate or stress
Creep – deformation under a constant force
Stress relaxation – force necessary to maintain a constant strain
The rheometer is able to perform viscosity measurements that extend far beyond the limits of a traditional viscometer, characterizing non-Newtonian behaviors like shear thinning, thixotropy, and yield stress of complex fluids (emulsions, suspensions, paints, inks, coatings, slurries). Heating can also be used in order to generate time-temperature superposition plots that allow for the comparison of materials almost regardless of their flow behavior at a given shear rate.
Prior to running samples, understanding some of the principals of the methodology is highly recommended: