DMA analysis is an advanced technique that optimizes material performance by precisely characterizing their viscoelastic properties. Used to study polymers, composites, and elastomers, it reveals the behavior of a material subjected to mechanical stress as a function of temperature, frequency, and time. From the glass transition to damping, DMA analysis helps define the limits of a material's use and adjust its formulation or processing method. It has become an essential tool in research, development, and quality control.
Table of Contents
What is dynamic mechanical analysis (DMA)?
An advanced thermal analysis technique
Dynamic mechanical analysis, or DMA , is a thermal analysis technique used to evaluate the mechanical properties of a viscoelastic material when subjected to oscillatory deformation. Unlike a conventional static test (tensile or compressive), DMA measures a material's response to dynamic stress at varying frequencies and temperatures.
The principle involves applying a periodic stress – typically a sinusoidal wave – to a sample and recording its resulting deformation. This mechanical response is analyzed as a function of time and the phase shift between the applied force and the measured deformation, allowing the elastic and viscous components of the material to be characterized.
Understanding viscoelasticity
Polymer, elastomer, and composite materials exhibit mechanical behavior intermediate between that of perfectly elastic solids and perfectly viscous fluids. This behavior is called viscoelastic. It depends on numerous parameters such as temperature, time, frequency of stress, and the molecular structure of the material (degree of cross-linking, molar mass, crystallinity, etc.).
DMA allows this response to be precisely quantified through various parameters:
- Storage module (E') : measures the elastic stiffness of the material (capacity to store mechanical energy);
- Loss modulus (E'') : measures the viscous component (capacity to dissipate energy in the form of heat);
- Tan delta (tan δ = E'' / E') : ratio between the two moduli, also called damping factor;
- Complex module (E) : vector combination of modules E' and E'', expressed in complex form.
The shape of the curves obtained during a DMA test (E', E'', tan δ as a function of temperature or frequency) makes it possible to identify key areas such as the glass transition, the rubbery zone or the fluid zone of a material.
A method that complements other techniques
Dynamic mechanical analysis (DMA) belongs to the family of thermal analysis methods, alongside differential scanning calorimetry (DSC), thermogravimetric analysis ), and thermomechanical analysis (TMA). Unlike these techniques, DMA does not directly measure changes in mass or heat, but rather the mechanical response of the material.
It is more sensitive than DSC for detecting the glass transition temperature (Tg), particularly in the case of highly filled, crosslinked, or composite materials. It also allows the detection of secondary transitions (β, γ), invisible with other methods.
In the laboratory, DMA is often used in conjunction with other analyses to obtain a complete view of a material's behavior:
- DSC for glass transition and melting temperatures;
- TGA for thermal stability and decomposition;
- TMA for coefficients of thermal expansion and deformations under constant load.
This complementarity allows for in-depth thermal and mechanical characterization, essential in the plastics, cosmetics, packaging and healthcare sectors.
How does a DMA analysis work?
The physical principle of dynamic deformation
Dynamic dynamics (DMA) analysis is based on a fundamental principle: the application of a periodic to a material, generally in the form of a sinusoidal wave , and the measurement of the resulting deformation . This dynamic loading allows observation of the material's response in terms of stiffness, damping capacity, and viscoelastic behavior, under controlled conditions of temperature , frequency , amplitude , and time .
When a material is subjected to this oscillatory stress, the deformation it undergoes is not perfectly in phase with the applied force. A time lag , called shift (δ) . This phase shift is directly related to the viscous of the material's behavior: the more energy the material dissipates (in the form of heat), the greater the phase shift.
This phase shift allows us to decompose the mechanical response of the material into two components:
- elastic component (in phase with the stress) represented by the storage modulus E' ;
- viscous component (in quadrature phase) represented by the loss modulus E'' .
The vector sum of these two components gives the complex modulus E *:
E *= E' +i E''
The ratio E''/E' gives the loss factor or tan δ , a key indicator of the material's ability to dampen vibrations. This value is particularly important in the automotive and electronics sectors, where reducing vibration and noise is a performance imperative.
The parameters controlled during a DMA trial
The strength of DMA analysis lies in its ability to vary several parameters in a precise and controlled manner:
- Temperature : The sample is placed in a temperature-controlled chamber that can cover a wide range, generally from −150 °C to +600 °C depending on the equipment. This variation allows for the detection of phase transitions (Tg, Tm) and the study of mechanical behavior at high or low temperatures.
- Frequency : This corresponds to the speed at which the stimulus is applied. It can vary from a few millihertz to several hundred hertz. Frequency analysis allows for the simulation of various dynamic loading conditions (slow or fast vibrations).
- Amplitude/deformation : The amplitude of the applied stress must remain within the linear of the material for the results to be usable. If the amplitude is too high, the behavior may become nonlinear, rendering the modulus calculations invalid.
- Time/Isothermal or Ramp Mode : The test can be performed at a constant temperature (isothermal mode) or with continuous variation (ramp mode), with typical heating rates of 1 to 10 °C/min. Some tests extend over several hours to monitor the evolution of mechanical properties over the long term.
Modern instruments also allow for double scans , combining frequency and temperature variations, to construct master curves representing the behavior of a material over a very wide range of stresses.
The different methods of solicitation
The sample is fixed onto a sample holder adapted to its shape and nature, then subjected to a precise stress test, depending on the property to be studied:
- Tension-compression : used for solid materials such as rigid polymers, composites, or certain elastomers. This mode allows access to the dynamic Young's modulus (E*).
- Bending : commonly used for films, filled polymers, or thermosets. The three-point bending allows for the simulation of stresses close to those encountered in real-world applications (beams, shells, etc.).
- Shear : often applied to pasty, viscous or liquid materials (e.g., glues, varnishes, inks). It allows the determination of the shear modulus G * and the dynamic viscosity η *.
Each type of deformation requires a sample geometry . For example, for a tensile test, the sample must be slender (parallelepiped or cylindrical type), while a shear test will be carried out on a shorter and more massive sample, often in a dedicated cell.
The DMA device automatically calculates viscoelastic moduli from the measured force and imposed deformation , taking into account the exact geometry of the sample.
Common testing methodologies and protocols
Several types of DMA tests are performed depending on the objective:
- Thermal scanning : measurement of mechanical properties as a function of temperature, to detect transitions (glassy, rubbery, fluid). It is one of the most common tests in the laboratory.
- Frequency scanning : useful for simulating vibration or cyclic loading conditions. Allows the construction of predictive models of vibration or damping behavior.
- Creep tests : application of a constant stress and measurement of deformation over time. Represents the material's ability to deform slowly under continuous load.
- Stress relaxation tests : measurement of the progressive decrease in stress in a material under constant deformation. Allows prediction of long-term behavior .
- Dynamic fatigue testing : replication of stress cycles over long periods to identify mechanical limits before failure or loss of performance.
Each test is programmed via a control software (e.g. Dynatest), which automatically manages temperature ramps, plateaus, frequencies and data recording.
Depending on the requirements, a DMA test can last from a few minutes (simple isothermal test) to several hours (slow thermal sweep with a stabilized plateau). The results are then analyzed in the form of curves, tables, or mathematical models, according to applicable standards (ISO 6721, ASTM D4065, etc.).
All of these parameters make DMA a highly versatile , capable of reproducing a wide variety of mechanical and thermal stresses, while providing accurate and reproducible data on the durability and performance of materials.
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What materials can be analyzed by DMA?
A method suitable for many polymer materials
One of the major advantages of dynamic mechanical analysis is its applicability to a wide variety of materials, particularly polymers. Thanks to its multiple stress modes (tension, bending, shear), DMA can test solid materials as well as flexible films, foams, adhesives, and semi-liquid products.
The main materials targeted are:
- Thermoplastic polymers , often used in packaging, electronics, and automobiles, exhibit highly temperature-dependent mechanical behavior. DMA (Dynamic Modulation Analysis) allows for the characterization of their stiffness, elasticity, and vibration resistance across a wide range of conditions. Examples include polypropylene, polycarbonate, and PET.
- Thermosetting polymers , such as epoxy, polyurethane, or phenolic resins, are irreversibly cross-linked and exhibit stable thermomechanical properties. DMA analysis allows for the evaluation of their glass transition temperature (Tg), fatigue resistance, and the impact of post-curing.
- Elastomers : highly deformable materials such as natural rubber, silicone, or styrene-butadiene copolymers. DMA is essential for analyzing their behavior in bending or shear, particularly their damping factor (tan δ), their cold stiffness, or their dynamic behavior at high frequencies.
- Polymer matrix composites : these materials reinforced by fibers (glass, carbon, flax) are studied in DMA to evaluate their mechanical strength in bending, their fatigue behavior, and their anisotropy (influence of fiber orientation on performance).
- Films and fibers : whether food films, textile fibers, or medical devices, DMA allows testing of their tensile strength, flexibility, and thermal stability. These thin materials require precise test conditions (small sample sizes, low deformation amplitudes).
- Solid pharmaceutical materials : In the case of tablets or capsules, DMA analysis allows verification of mechanical stability and the evolution of viscoelastic properties as a function of temperature and humidity. These tests are useful for packaging and storage.
Specific materials and special cases
In addition to conventional materials, DMA can be used to test more complex samples or those from constrained environments:
- Polymers for medical devices : prostheses, implants, catheters… These products require high mechanical stability and biocompatibility. DMA helps predict their behavior under physiological conditions (37°C, high humidity, prolonged mechanical stress).
- Bio-based or recycled materials : PLA, PHA, natural fibers (flax, hemp), recycled elastomers… These materials often exhibit significant variability related to their origin or manufacturing process. DMA analysis allows for the evaluation of their performance, thermal transition, and lifespan.
- Multilayer composite materials : used in flexible packaging, membranes or technical textiles, they require a fine characterization of interfaces and energy dissipation.
- Technical adhesives and glues : widely used in aerospace, automotive, and electronics, adhesives must guarantee mechanical strength, controlled flexibility, and good aging stability. DMA (Dynamic Material Analysis) allows monitoring their curing, analyzing their damping capacity, and determining their shear modulus.
- Materials in extreme conditions : some DMA tests can be carried out at very low temperatures (−150 °C) or very high temperatures (+600 °C), allowing the simulation of real conditions of use in the aerospace, nuclear or industrial equipment sectors.
Concrete industrial applications
DMA analysis is used in many sectors to support the development of new materials, control production quality, or understand the causes of failure. Here are some examples of concrete applications:
- Automotive : evaluation of the durability of seals, silent blocks, or dashboard components subjected to vibrations. Study of the thermal behavior of interior materials exposed to solar radiation.
- Aeronautics : characterization of structural composites, optimization of the weight/stiffness ratio, prediction of aging under thermal cycles.
- Packaging : testing the flexibility of films, the mechanical resistance of trays, and the thermal resistance of multilayer materials.
- Cosmetics : analysis of polymers present in packaging or textures, study of the dimensional stability of bottles under mechanical stress.
- Electronics : validation of polymers for flexible printed circuits, analysis of component fixing adhesives, prediction of viscoelastic behavior under heating.
- Food processing : damping test in insulation or cushioning materials, evaluation of the thermal stability of coatings or packaging in contact with foodstuffs.
In all these cases, DMA provides precise , quantifiable and reproducible , enabling manufacturers to make informed decisions regarding formulation, material selection or market strategy.
What is the purpose of a DMA analysis?
Determine the glass transition temperature (Tg)
One of the first applications of DMA is the determination of the glass transition temperature (Tg) of a polymer material. This temperature corresponds to a critical threshold beyond which a polymer transitions from a rigid, glassy state to a more flexible, rubbery state. It is essential for defining the range of applications of a material.
In a DMA assay, this transition is detected by analyzing the tan δ curves as a function of temperature . The peak in tan δ generally indicates the glass transition temperature. Unlike other techniques such as DSC, DMA is capable of detecting this transition with very high sensitivity, even in highly filled, crosslinked, or composite materials.
Tg is a key parameter in many sectors:
- In packaging: to guarantee the mechanical strength of trays or hot films.
- In cosmetics: to ensure the stability of bottles or formulation materials.
- In aeronautics: to verify the performance of composites subjected to significant thermal variations.
Studying the rigidity and elasticity of materials
DMA analysis provides detailed information on mechanical stiffness , notably through the storage modulus (E') , which reflects its ability to resist elastic deformation. This modulus is measured under different thermal regimes to track the evolution of the material's stiffness during heating.
The resulting curves allow us to visualize several characteristic areas:
- Glassy zone : the material is rigid (high E'), generally brittle.
- Transition zone : the modulus drops rapidly, the material becomes viscoelastic.
- Rubbery zone : the material regains elastic behavior but with a much lower modulus.
DMA thus makes it possible to compare different formulations, to evaluate the effect of heat treatment, aging, or the presence of additives (plasticizers, fillers, crosslinkers).
It is also used to calculate the dynamic Young's modulus (E) * and, in some cases, Poisson's ratio , by combining the results of tension and shear.
Analyze the vibration damping capacity (tan δ)
The loss factor (tan δ) is a key indicator of damping behavior . It measures the material's ability to dissipate mechanical energy (vibrations, shocks, deformations) as heat through internal friction.
A high tan δ means that the material absorbs vibrations well (good damper), while a low tan δ indicates a more rigid and less dissipative behavior (like a metal).
This property is crucial in:
- The automotive industry (silent blocks, dashboards, seals),
- The building (vibration-damping insulation),
- Electronic equipment (supports, fixings, sheaths),
- Sports equipment (soles, materials for rackets or skis).
DMA analysis makes it possible to identify the temperature and frequency ranges where tan δ is maximal, i.e. where the material offers its best damping performance.
Understanding the long-term behavior of materials
In addition to temperature and frequency measurements, DMA is used for isothermal , such as:
- Creep of the deformation over time.
- Stress relaxation : maintaining a constant deformation and measuring the decrease in the force required.
- Dynamic fatigue tests : repeated stress cycles to simulate prolonged usage conditions.
These tests make it possible to predict the long-term behavior of the material , under conditions close to reality: thermal cycles, repeated stresses, accelerated aging.
For example :
- A prosthetic polymer must retain its flexibility after several years of use.
- A structural adhesive must not lose its adhesion after prolonged exposure to heat.
- A composite material for an engine hood must withstand heating/cooling cycles without cracking.
These tests are essential for product validation , life cycle simulation , or compliance with industry standards .
Facilitating the selection and formulation of materials
DMA is a strategic tool for R&D teams , formulators , and materials engineers . Thanks to the precise mechanical data it provides, it is possible to:
- Compare several raw materials or formulations,
- Choose the material best suited to a given application (rigid, flexible, shock-absorbing…),
- Optimizing a manufacturing process (post-hardening, extrusion, molding…),
- Adjust the rate of plasticizer, filler or crosslinker in a formulation.
It is also an excellent tool for analyzing the effects of a defect : modification of the modulus, drop in Tg, loss of elasticity… DMA analysis makes it possible to identify a non-conformity or premature aging, in order to correct the formulation or the process.
How to interpret the results of a DMA analysis?
Reading DMA curves: magnitudes and loss factor
The results of a DMA analysis are often presented as curves representing the different parameters measured during the test: storage modulus (E') , loss modulus (E'') , tan δ , and complex modulus (E) * as a function of temperature or frequency. These curves provide a comprehensive view of the material's mechanical behavior and allow for the identification of several key points.
Storage module (E')
The storage modulus (E') is a measure of the elastic stiffness of the material. It indicates the material's capacity to store applied mechanical energy. In a temperature-dependent curve of E', we can observe:
- An increase in rigidity in the vitreous zone (rigid material),
- A decrease in stiffness in the transition zone (change of state of the material),
- Stabilization of rigidity in the rubbery zone (flexible material).
The position of the glass transition temperature (Tg) can be easily spotted by the marked drop in the storage module.
Loss modulus (E'')
The loss modulus (E'') quantifies the viscous component of the material, that is, its ability to dissipate energy as heat. The more energy a material dissipates, the higher its loss modulus. In a DMA analysis, this curve shows:
- A loss peak associated with the glass transition temperature (Tg), where the material transitions from a rigid state to a more flexible state.
- A reduction in the loss modulus in the rubbery zone, when the material becomes more flexible.
The intensity of this peak can also indicate the damping of the material, a characteristic sought after in many industrial sectors such as automotive or electronics.
Tan δ (loss factor)
The loss factor (tan δ) is the ratio between the loss modulus and the storage modulus (E'' / E'). This value is a key indicator of the material's damping behavior. A high tan δ means the material dissipates a large amount of energy (for example, a shock absorber), while a low tan δ indicates a stiffer and more elastic material.
- In the glassy zone, tan δ is small because energy dissipation is low.
- In the transition zone, tan δ increases considerably, reaching its maximum around Tg.
- In the rubbery zone, tan δ remains high, but energy dissipation is more stable, meaning the material is more flexible but less dissipative.
Complex module (E*)
The complex modulus (E) * is the vector combination of the storage modulus and the loss modulus. It represents the overall response of the material to dynamic loading, integrating both its capacity to store and dissipate energy. Depending on the temperature or frequency, this curve can provide information on the transition between stiffness and flexibility , the glass transition , and the dynamic response of the material under different conditions.
Analysis of transition temperatures and behavioral zones
One of the major advantages of DMA is its ability to precisely detect transition temperatures . These transitions mark significant changes in the material's mechanical properties, which are crucial for its use in real-world applications.
Glass transition temperature (Tg)
The temperature at which a polymer transitions from its glassy (rigid and brittle) state to a more flexible and rubbery state is called the Tg thermal and mechanical of a material. DMA curves allow for the precise localization of this temperature, which is often associated with a peak in the tan δ curve.
Thermoplastic materials, such as polycarbonate or polymethyl methacrylate (PMMA) , have relatively high Tg values, while elastomers like natural rubber have a much lower Tg value. This information is crucial for determining the material's usage conditions.
Rubber transition temperature (Tc)
The rubber transition (Tc) refers to the point at which a material, after transitioning from a glassy to a rubbery state, enters a reversible elastic behavior . This temperature is important for elastomers and polymers used in applications such as seals, tires, and shock absorbers. It can be determined by analyzing the tan δ curve, which shows a marked increase in damping capacity.
Interpretation of results according to the application
The results obtained by DMA must be interpreted in light of the specific requirements of each sector. Depending on performance needs , the material selection criteria may vary.
In the automotive industry
In the automotive industry, for example, mufflers , tires , and seals are subjected to vibrational and thermal stresses. DMA analysis allows testing of damping capacity (tan δ), determination of thermal stability , and assurance of material durability under temperature variations. The results should demonstrate good damping within the operating temperature ranges of vehicles.
In electronics
In the electronics sector, materials used for flexible components or encapsulants must be able to withstand mechanical stresses while maintaining their thermal integrity . DMA allows verification that these materials have a sufficiently high glass transition temperature (Tg) to prevent deformation under high operating temperatures.
In food packaging
DMA analysis of packaging materials ensures that plastic films or food packaging components withstand temperature variations and retain their mechanical properties throughout the product's lifecycle. Migration and thermal stability are crucial for ensuring food safety.
Precautions and best practices for interpretation
When interpreting DMA results, it is essential to take into account several external factors :
- Sample preparation : Samples must be prepared uniformly and sized correctly for each type of test (tensile, flexural, shear).
- Test conditions : Temperature, humidity, and pretreatment of materials (e.g., aging or UV exposure) can influence the results.
- Comparability of results : Comparing the results obtained with those of reference materials or industry standards allows us to validate the data and ensure their relevance for the target application.
By adhering to these best practices, the data obtained via DMA not only allows for the control of material quality but also guides the research and development of new products.
Why choose DMA analysis for your materials testing?
The advantages of DMA analysis for polymer materials
Complete characterization of mechanical properties
Dynamic mechanical analysis (DMA) allows for the detailed and precise characterization of the elastic and viscous of polymers. Unlike other techniques, DMA simultaneously measures several essential parameters, including the storage modulus (elastic stiffness), the loss modulus (energy dissipation), and the loss factor (tan δ) , thus enabling an in-depth analysis of dynamic mechanical behavior . This characterization is crucial for optimizing materials for specific applications, such as seals, packaging materials, or automotive components.
Detection of critical thermal transitions
One of the major applications of DMA is the detection of glass transition temperatures (Tg) , which is fundamental for evaluating the thermal stability of polymers. The ability to accurately determine this temperature allows for a better understanding of how a material reacts under different temperature conditions, which is particularly important for applications subject to thermal variations (tires, automotive parts, packaging materials).
Monitoring aging and durability
DMA is also used to simulate the aging of materials, thus enabling the evaluation of their long-term durability Stress relaxation and creep tests performed in isothermal mode are essential for predicting the behavior of materials under prolonged use. This allows manufacturers to anticipate potential failures and improve material formulations to ensure longevity.
A reliable and flexible method for diverse sectors
One of the main advantages of DMA lies in its flexibility of application to a wide range of materials and in very diverse sectors. Here are some examples of areas where DMA plays a key role:
Automotive and Aerospace
In the automotive and aerospace , DMA is used to test materials subjected to extreme temperature and vibration . It allows for the validation of the performance of composites used in structures, the testing of the resistance of seals to thermal and mechanical variations, and the guarantee of the stability of interior materials in vehicles or aircraft.
Packaging and food safety
In the food , DMA (Discharge Analysis Method) is used to test plastic films , barriers , and other packaging materials that come into contact with food products. Migration and thermal stability ensure that the materials used do not alter product quality and comply with safety standards, such as EC Regulation No. 1935/2004.
Medical and pharmaceutical devices
DMA analysis is also crucial in the field of medical devices and pharmaceutical materials , where biocompatibility and mechanical stability are paramount. Materials used for implants, prostheses, and drug delivery devices must be tested for their long-term strength and stability under mechanical and thermal stresses .
Electronics and sensitive equipment
In the electronics , DMA is used to test the rigidity and flexibility of flexible components such as flexible printed circuit boards . These materials must guarantee reliable performance under different temperature and mechanical stress conditions.
The reliability and accuracy of the results obtained
Another major strength of DMA analysis is the reliability of the results it provides. The use of state-of-the-art equipment viscoanalytical instruments (e.g., the METRAVIB RDS VA2000), makes it possible to perform tests with exceptional accuracy , even on materials exhibiting complex behaviors .
Quality and compliance standards
Accredited laboratories using DMA, such as those certified to ISO 17025 and COFRAC , guarantee that tests are performed according to current international standards quality , safety , and performance required by industries. This is particularly important for highly regulated sectors, such as food, pharmaceuticals, and aerospace.
Repeatability and reproducibility of tests
Thanks to standardized test protocols , DMA offers repeatability and reproducibility of results, allowing manufacturers to track changes in material properties over time and validate changes to formulation or manufacturing process.
A strategic choice for R&D and product optimization
The use of DMA in laboratories allows companies to conduct research and development by rapidly evaluating the and mechanical properties of materials before they enter production. This optimizes manufacturing processes , reduces validation testing costs consistent quality throughout production.
Accelerating the development cycle
DMA analysis helps reduce time to market by providing reliable and readily actionable data for new product development. By precisely adjusting material formulations and evaluating their behavior before production, companies can improve process efficiency while meeting performance requirements.
Optimizing material performance
By adjusting parameters such as chemical composition , additives , or crosslinking , DMA helps manufacturers achieve optimal mechanical properties for each specific application. This ensures that materials meet not only technical requirements but also environmental standards .
