Rheometrische Ausstattung
ARES : strain-controlled dynamic mechanical rheometers (ARES, ARES-G2)
(TA Instruments)
The visco-elastic or rheological properties of polymers can be easily determined from dynamical-mechanical experiments as a function of time, frequency and temperature. Their understanding is important for the design of new materials as well as for optimizing processing conditions of known polymers. The response to linear or non-linear deformation is highly sensitive even to the architecture of the polymer chain. Probing a sample isothermally over one specific frequency range or time domain yields typical storage and loss moduli which can be shifted by the time-temperature-superposition principle to any reference temperature to cover several magnitudes in the (unmeasured) time or frequency range. The full relaxation time spectrum can then be obtained as well and quantitative comparisons with theoretical expectations from microscopic approaches are feasible. The results complement typical time-dependent scattering methods like neutron spin-echo spectroscopy or quenched small angle neutron scattering and the dielectric response functions.
Angular frequency | 0.001-500 rad/s |
Torque 2kN FRT transducer | 2-2000 g |
Temperature | -150°C < T <350°C |
Temperature controller | Liquid N2 /Peltier/Water bath/Air |
Tools | Parallel plate, cone-plate (0.04 rad), torsion, couette, extensional viscosity,fiber |
Q800: stress-controlled dynamic-mechanical analysis
(TA Instruments)
Dynamic Mechanical Analysis (DMA) differs from the strain-controlled rheometer by application of an oscillating force to a sample and by the analysis of the dynamic response to this stress. From this, one calculates properties like the tendency to flow (called viscosity) from the phase lag and the stiffness (modulus) from the sample recovery. These properties are often described as the ability to lose energy as heat (damping) and the ability to recover from deformation (elasticity). In this way the relaxation spectrum of polymer chains can be studied. The method complements the strain-controlled experiments because stress-controlled mesurements are ideally suited for creep measurements to long times which cannot be accessed easily by rheometers due to the limited frequency range.
Angular frequency | 0.01-200 Hz |
Modulus range | 103-1012 Pa (±1%) |
Temperature | -150°C < T <600°C |
Temperature controller | Liquid N2 /Air |
Tools | Shear sandwich, single-dual cantilever,3-point bending, tension) |
AR-G2 rheometer:
(TA Instruments)
The AR-G2 is a stress-controlled rheometer with a special magnetic bearing that allows measurements of torques in the nano-Nm range typical for low viscosity samples. Together with its high angular resolution of 0,025 μrad it is therefore especially dedicated to fluid rheology and high resolution creep and stress relaxation experiments.
An additional small angle light scattering option (CCD) allow insitu structural characterisation in Q vector range ~1.38x10-4Å-1 to 6.11x10-4Å-1 (scattering angle ~6° to 26.8°).
Angular frequency | 0.01-200 Hz |
torque range | 30nNm – 200mNm |
Angular resolution | 0.025 μrad (with 300rad/s) |
Temperature controller | Peltier, Liquid circulator |
Tools | Cone-plate, parallel plate, concentric cylinders (Searle) |
Kontakt:
Phone: +49 2461 61-6683
email: j.stellbrink@fz-juelich.de
Phone: +49 2461 61-4681
Email: w.pyckhout@fz-juelich.de
