## Rheometer

In dynamic rheology measurement, a continuously increasing and decreasing strain is applied to a material in a certain frequency range and the phase difference between strain and stress is measured with the highest stress value. If the material behaves as an ideal elastic material, the stress generated is directly proportional to the strain, and the stress and strain signals are in phase. The behavior of an ideal elastic material is represented by Hooke's Law. For an ideal viscous material, stress and strain rate are directly proportional, and there is a 90 degree phase difference between stress and strain. The behavior of an ideal viscous material is represented by Newton's Law. For viscoelastic materials, the phase difference between stress and strain takes a value between elastic (0º) and viscous (90º) behavior.

The tension signal of a viscoelastic material can be divided into two parts:

- Elastic stress in phase with strain.
- Viscous voltage with 90º phase difference with strain.

The Storage Modulus (E') (the ratio of elastic stress to strain) represents the ability of a material to store energy elastically. The Loss Modulus (E'') (ratio of viscous stress to strain) represents the ability of a material to dissipate energy. The complex modulus (E*) represents the total resistance of a material to deformation.

**Instrument:** TA Instruments ARES Rheometer

**Specifications**

- Heating Rate = 0.1 - 50 ºC/min.

Temperature range = Room temperature - 600 ºC

Frequency Range= 10-5 - 500 rad/s

**Measurement Modes and Sample Requirements**

- Parallel Plates: Diameter = 8mm, 25mm, & 40mm
- Cone and Plate: Diameter= 25 mm
- Bending (Rectangular Example): Length ~ 45 mm, Max. Width=12.7, Max. Thickness = 12.7mm
- For parallel plates and Cone and Plate measurement modes, 50 ml of sample is sufficient.

**Applications**

- Polymers
- Polymer blends
- Composites
- Molten polymers
- Medium to highly viscous liquids.

In dynamic rheology measurement, a continuously increasing and decreasing strain is applied to a material in a certain frequency range and the phase difference between strain and stress is measured with the highest stress value. If the material behaves as an ideal elastic material, the stress generated is directly proportional to the strain, and the stress and strain signals are in phase. The behavior of an ideal elastic material is represented by Hooke's Law. For an ideal viscous material, stress and strain rate are directly proportional, and there is a 90 degree phase difference between stress and strain. The behavior of an ideal viscous material is represented by Newton's Law. For viscoelastic materials, the phase difference between stress and strain takes a value between elastic (0º) and viscous (90º) behavior.

The tension signal of a viscoelastic material can be divided into two parts:

- Elastic stress in phase with strain.
- Viscous voltage with 90º phase difference with strain.

The Storage Modulus (E') (the ratio of elastic stress to strain) represents the ability of a material to store energy elastically. The Loss Modulus (E'') (ratio of viscous stress to strain) represents the ability of a material to dissipate energy. The complex modulus (E*) represents the total resistance of a material to deformation.

**Instrument:** TA Instruments ARES Rheometer

**Specifications**

- Heating Rate = 0.1 - 50 ºC/min.

Temperature range = Room temperature - 600 ºC

Frequency Range= 10-5 - 500 rad/s

**Measurement Modes and Sample Requirements**

- Parallel Plates: Diameter = 8mm, 25mm, & 40mm
- Cone and Plate: Diameter= 25 mm
- Bending (Rectangular Example): Length ~ 45 mm, Max. Width=12.7, Max. Thickness = 12.7mm
- For parallel plates and Cone and Plate measurement modes, 50 ml of sample is sufficient.

**Applications**

- Polymers
- Polymer blends
- Composites
- Molten polymers
- Medium to highly viscous liquids.