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Last revision: 01 March 2007
Dynamic mechanical analysis (DMA) and Dielectric analysis (DEA) are two widely used techniques for the characterization of polymers. Combining the two techniques allows incremental information to be obtained about the behavior of for instance polymer systems. Simultaneous DMA-DEA measurements are achieved using the DMA parallel plate, or cup and plate, measuring system, simultaneously, as electrodes for the DEA. Another option for simultaneous measurement is to use a surface detecting interdigitated electrode sensor in the DMA to obtain DEA measurements.
What does a dynamic mechanical analyzer measure?
Dynamic mechanical analyzers measure changes in mechanical behavior, such as modulus and damping, as a function of temperature, time, frequency, stress or strain or combinations of these parameters.
Principle of operation
The Perkin-Elmer DMA7e allows for the quantitative mechanical analysis of a broad range of sample materials. The system is made up of four segments: a linear force motor, a temperature controlled displacement detector (LVDT), a central core rod and probe (measuring system) assembly and an environmental system (furnace).
The central core rod runs the length of the analyzer and is the device through which all stresses are applied to the sample. Measuring systems and probes are attached at the lower end of the core rod through the use of a quick-connect fixture. This fixture allows the rapid installation or removal of the measuring systems.
The temperature controlled displacement detector is the measuring system on the DMA7e. Mounted in a vertical arrangement, it accurately tracks any mechanical changes occurring in the sample.
A linear force motor is used with the DMA7e to provide precise control of all stresses applied to the sample. The high resolution of the force motor allows for reproducible force control up to 1 mN. All stresses applied are maintained constant throughout the experiment to produce the best quality data and results.
DMA7e Cut-Away diagram (Perkin Elmer slide)
What does a Dielectric analyzer measure?
Dielectric analyzers measure the relative mobility of charged sites in a polymer. Charged sites in a polymer are typically ions and dipoles.
Principle of operation
The mobility of ions and dipoles is measured by applying a sinusoidal voltage to the sample and measuring the current.
DEA Excitation and Response
The applied voltage produces a polarization within the sample and causes a change in the amplitude of oscillation, measured in dB, and a phase shift measured in degrees. The amplitude change and the phase shift are measured by comparing the applied voltage to the measured current at the response electrode.
DEA Ionic and Dipolar behavior
This signal may either pass through the sample in a classical parallel plate-type measurement, or in a fringing field measurement typical of two interdigitated electrodes fixed on a planar substrate.
This current can be resolved into two fundamental dielectric characteristics: capacitance and conductance. From these, dielectric properties can be determined as a function of time, temperature, and frequency.
Simultaneous results are obtained using traditional DMA parallel plates (or cup and plates) as electrodes for the DEA. More can be obtained from the combined techniques than the individual techniques. DMA-DEA can be used for most thermosets, hot melt adhesives, elastomers, thermoplastics and curing elastomers.
Setup for simultaneous analysis (Perkin Elmer slide)
Advantages
- Faster analysis time – only one run is required.
- Sample is exposed to identical environmental conditions.
- Sample is exposed to identical temperature conditions.
- Sample preparation is identical.
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The DMA7e is very versatile due to the range of measuring systems that can be used.
These include:
- Parallel plate measuring system with:
- parallel plates
- sintered parallel plates
- parallel plates with tray kits
- cup and plate
- 3 Point bending measuring system
Extension measuring system
DMA7e analyzer specifications
Furnace (28 mm diameter)
- -170 to 500 oC (rate up to 40 oC/min)
Force that can be applied
- 1 to 8000 mN downwards
- 6500 mN upwards
Modulus
- 104 to 1012
Frequency
- 0.01 to 51 Hz
Sample geometries
It can be:
- flat bars
- pellets
- cylinders
- disks
- films
- fibers
Low conductivity option
Specifications
Bulk conductivities 10-16 to 10-5 Siemens/cm Ion viscosity 105 to 1016 Ohm-cm Sensor Low conductivity Operating frequency range 0,001 to 100 000 Hz
Mid conductivity option
Specifications
Bulk conductivities 10-13 to 10-3 Siemens/cm Ion viscosity 103 to 1013 Ohm-cm Sensors IDEX User sensor Operating frequency range 1 to 100 000 Hz The DMA and DEA can also be used combined.
- Temperature Scan
- Time Scan
- Frequency Scan
- Creep-Recovery
- Constant Force (TMA)
TEMPERATURE SCAN
Measurement Use Modulus Impact performance Damping Dimensional stability Tan delta Thermal transitions Glass Transition Multiphase charcterisation Crystalline transitions Copolymerisation Melt transitions Processing Parameters Alpha transitions Degree of Polymerization Beta transitions Effect of plasticiser Gamma transitions Backbone mobility Secondary dispersions Ductility
Crystallite morphology
Thermal history
Annealing
FREQUENCY SCAN
Measurement Use Dynamic viscosity Melt viscosity Zero shear viscosity Molecular weight Terminal zone modulus Molecular structure Absolute modulus Blend ratios Frequency multiplexing Process parameters Crossover Molecular weight distribution Fingerprinting
Detect subtle material differences
STRESS SCAN
| Measurement | Use |
| Slope | Young's modulus |
| Critical stress | Proportional limit |
| Proportional area | Energy for brittle fracture |
| Yield strength | Load capacity |
| Yield point | Strength |
| Ultimate stress | Toughness |
| Elongation to break | Ductility |
| Loss modulus | Heat generated per cycle |
| Prot test | Fatigue life |
| Yield strength/density | Failure envelope |
| Young’s modulus | Specific strength Specific modulus Strain hardening Crystal-crystal interaction Crystal re-orientation |
Complete dynamic and dielectric analysis of samples can be done through the use of the right mode of operation and in conjunction with the DEA.
The following is some of the test that can be performed on samples:
- melt, Tg, alpha, beta and gamma transition
- recrystallization
- curing
- modulus
- damping
- creep
- shrinkage
- heat deflection
- brittle point test
- tensile test
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