Thermal Analysis in the Field of Renewable Energy
On Demand Webinar

Thermal Analysis Applied to the Field of Renewable Energy

On Demand Webinar

This webinar explores the various uses of thermal analysis in the field of renewable energy

Renewable energy
Renewable energy

Increasing demand of a cleaner environment led to several developments in the field of renewable energy sources. Hence, in the last decades solar energy-, wind energy- or biomass plants are widely in use worldwide. The four main techniques of thermal analysis DSC, TGA, TMA, and DMA are ideal for characterizing materials that are common in these fields.

In this Webinar, we will discuss the different methods used to investigate important materials for renewable energy sources and present some interesting applications.

43:40 min
English

The Webinar covers the following topics:

  • Introduction
  • Basic properties of thermoplastics
  • Typical questions
  • Thermal analysis
  • Industries and applications
  • Instrumentation and applications
    - Differential Scanning Calorimetry (DSC)
    - Thermogravimetry (TGA)
    - Thermomechanical Analysis (TMA)
    - Dynamic Mechanical Analysis (DMA)
  • Summary

In recent years, renewable energy resources have become widely accepted as a way to help solve the world’s potential energy crisis. Developments are progressing rapidly and new materials employed in the field of renewable energy require adequate quality control.

Industrial applications

Methods based on thermal analysis techniques such as DSC, TGA, TMA, DMA are extremely important for characterizing the materials and compounds used in renewable energy resources. Thermal analysis is mainly used to measure the thermal stability, oxidative stability, and curing behavior of materials. In addition, it is an important tool for optimizing processes in biomass plants or for quality control in the biofuels industry.

Other important applications have to do with the laminating process of photovoltaic modules and the measurement of the mechanical properties of composites used for rotor blades in wind turbines.

Thermal analysis in the field of renewable energy

The most important effects that can be analyzed by DSC are the glass transition, melting behavior, and the enthalpy of cure.

TOA is the method of choice for the visual observation of samples, for example during crystallization and to detect cloud point effects.

The main applications of TGA are content analysis, thermal stability and evaporation behavior.

TMA can be used to characterize expansion, shrinkage or melting behavior.

DMA is a good method for characterizing the viscoelastic behavior of materials.

Thermal Analysis in the Field of Renewable Energy

Slide 0: Thermal Analysis in the Field of Renewable Energy

 

Ladies and Gentlemen,

Welcome to the METTLER TOLEDO webinar on Thermal Analysis in the Field of Renewable Energy.

 

In recent years, renewable energy resources have become widely accepted as a way to help solve the world’s potential energy crisis. Developments are progressing rapidly and new materials employed in the field of renewable energy require adequate quality control.

Methods based on thermal analysis techniques such as DSC, TGA, TMA and DMA are extremely important for characterizing the materials and compounds used. During the course of this webinar, I want to describe a number of interesting application examples to demonstrate this. The applications have to do with the measurement of the physical properties and behavior of materials as a function of temperature and include melting, thermal stability and curing reactions.

 

Slide 1: Contents

The slide lists the topics I would like to cover.

First, I want to make some remarks about renewable energies in general.

I will then discuss the most important thermal properties of materials used in the field of renewable energy and describe the thermal analysis techniques that can be used to measure the properties.

The techniques include:

Differential Scanning Calorimetry, or DSC;

Thermo-optical Analysis, or TOA;

Thermogravimetric Analysis, or TGA;

Thermomechanical Analysis or TMA;

and Dynamic Mechanical Analysis, or DMA.

 

After this, I want to present a number of examples that illustrate how thermal analysis can be used to investigate the physical behavior of materials and compounds used in the renewable energy field.

 

Finally, I will summarize the different thermal analysis techniques and their application areas and list a number of useful references for further information and reading.

 

Slide 2: Introduction

During the last ten to twenty years, there has been a marked change to the use of more renewable and sustainable energies. This change has been catalyzed by the prospect of limited resources of fossil fuels, the greatly increased awareness of environmental and atmospheric problems, and the unsolved problems associated with the operation and decommissioning of nuclear power plants. On top of this, the widespread acceptance that nuclear power once enjoyed has been undermined in recent years by several serious accidents.

Renewable energy is energy derived from resources which are naturally replenished on a short timescale. These include hydro- and wind-power, biomass, solar energy, geothermal power, and biofuels. Related technologies such as fuel cells, batteries or energy storage systems utilize special compounds that can be investigated by thermal analysis.

Renewable energy and energy efficiency are the two main pillars on which sustainable energy is based. The aim of sustainable energy is to meet the energy needs of the present without compromising the environment or the needs of future generations.

 

Slide 3: Introduction

Typical questions that arise in connection with materials used in the field of renewable energy are:

 

Are you interested in the thermal stability of the compounds you use?      or

 

Do you need to test the oxidative stability of your products?                    or

 

Are you familiar with the curing behavior of the materials you use?

 

For example, in the wind energy industry, the degree of cure of epoxy resins used for the manufacture of laminated rotor blades for wind turbines has to be characterized. This can easily be done by DSC.

The picture on the right side shows the DSC heating curve of the curing reaction of an epoxy resin. Curing starts at about 30 degrees Celsius and is completed by 230 degrees. Integration of the area under the curve allows us to determine the energy produced in the curing process up until the temperature when the epoxy resin is fully cured.

 

Slide 4: Thermal Analysis

 

But let’s start at the beginning. What exactly is Thermal Analysis?

 

The ICTAC definition of thermal analysis is:

“A group of techniques in which a physical property of a substance is measured as a function of temperature whilst the substance is subjected to a controlled temperature program”.

The schematic diagram on the right shows a simple linear temperature program in which the temperature of a sample is increased at a constant heating rate.

 

The lower half of the slide illustrates typical events and processes that occur when a sample is heated. For example, the melting process in which the sample changes from the solid to the liquid state. Or oxidation - if the sample is exposed to air or oxygen it will start to oxidize and finally decompose.

We use thermal analysis techniques to investigate effects like this.

 

Slide 5: Thermal Analysis                                                                    Techniques

The slide shows the five most important techniques used in thermal analysis to characterize materials employed in the field of renewable energy, namely:

 

Differential Scanning Calorimetry, or DSC. This is the most widely used thermal analysis technique. The picture shows a DSC sensor with a crucible containing a sample (colored red), and a reference crucible.

Thermo-optical Analysis, or TOA. In the picture, we see a video camera installed above a DSC instrument.

Thermogravimetric Analysis, or TGA. The picture shows part of the TGA ultra-micro balance with its automatic internal ring weights.

Thermomechanical Analysis, or TMA. Here we see the sample area with a sample (colored red) and the quartz probe and sensor.

And finally, Dynamic Mechanical Analysis, or DMA. The picture shows one of the several different sample-clamping assemblies.

 

I will explain the different measurement principles and the properties that the instruments can measure in more detail during the course of the webinar and describe some typical application examples.

 

Slide 6: Industries and Applications

The table summarizes the most important industries and the different applications of thermal analysis in this field. It shows that thermal analysis is mainly used to measure the thermal stability, oxidative stability, and curing behavior of materials. In addition, it is an important tool for optimizing processes in biomass plants or for quality control in the biofuels industry.

Other important applications have to do with the laminating process of photovoltaic modules and the measurement of the mechanical properties of composites used for rotor blades in wind turbines.

 

Slide 7: Differential Scanning Calorimetry (DSC)

The first technique I want to discuss is DSC. DSC allows us to determine the energy absorbed or released by a sample as it is heated, cooled or held at constant temperature.

 

DSC instruments exist in different versions depending on their temperature range, the type of sensor, and the available heating and cooling rates.

 

The standard METTLER TOLEDO DSC 1 instrument measures from minus one hundred and fifty degrees Celsius (–150 °C) to plus seven hundred degrees (700 °C) at heating rates of up to three hundred Kelvin per minute (300 K/min). Samples are normally measured in small crucibles made of aluminum, alumina or other materials, using sample amounts of two to twenty milligrams.

 

Another useful DSC technique is high-pressure DSC, or HPDSC for short. The METTLER TOLEDO HP DSC 1 instrument can analyze samples under inert or reactive gases at pressures of up to ten megapascals (10 MPa) or 100 bar. This suppresses undesired vaporization of samples or enables the stability of samples under increased oxygen pressures to be studied.

 

The schematic curve on the left shows a typical DSC measurement curve of a semi-crystalline polymer. Exothermic effects point in the upward direction and endothermic effects downward. The different effects are numbered next to the curve and explained in the table, namely:

One, the initial deflection or start-up transient of the DSC;

Two, the baseline where no thermal effects occur;

Three, a glass transition with enthalpy relaxation;

Four, cold crystallization;

Five, melting of the crystalline fraction; and finally

Six, oxidative exothermic decomposition.

 

Slide 8: Differential Scanning Calorimetry (DSC)

DSC is used to study thermal behavior and events such as melting, crystallization, solid-solid transitions, and chemical reactions.

The table on the left summarizes the analytical applications of DSC for materials used in the field of renewable energy. The main applications have to do with melting behavior, crystallization, chemical reactions and curing behavior. The rate of curing reactions and the degree of cure of thermosetting matrixes are important parameters.

Several standard procedures are available for determining oxidative stability and crystallinity.

DSC measurements also provide information about the composition and the thermal history of materials as well as the enthalpy of transitions, specific heat capacity, and the influence of impurities, additives or fillers on melting behavior.

 

The picture on the right of the slide shows a view of an open DSC furnace with sample and reference crucibles. The standard crucibles are made of aluminum.

 

Slide 9: Application 1: HPDSC                                                Biodiesel

Biodiesel is being increasingly used as a fuel due to improved availability and competitive prices.

However, one problem is the risk of oxidation of unsaturated fatty acids present in the biodiesel. This leads to the formation of short chain lengths and rancidity that we know from vegetable oils. This is the reason why stabilizers are added to biodiesel and why stability tests are important for quality control.

In this example, the performance of different stabilizers was investigated using an OOT or Oxidation Onset Temperature measurement. To do this, an unstabilized biodiesel and two stabilized samples of biodiesels were measured in oxygen in an HP DSC 1 instrument from 30 degrees Celsius to 195 degrees at a heating rate of 5 Kelvin per minute. The oxygen pressure was 2 megapascals or 20 bar. The diagram displays the resulting OOT curves. We can see that the samples can be differentiated by their OOT onset temperatures.

The Oxidation Onset Temperature is a qualitative measure of the level of stabilization of a material toward oxidation. The measurement is performed at a specified heating rate in an oxidative environment of air or pure oxygen.

The HPDSC technique is a good test to quickly estimate the efficiency of different stabilizers in biodiesel.

 

Slide 10: Application 2: DSC                                                                EVA

A photovoltaic module consists of arrays of solar cells connected together. An important step in the manufacture of photovoltaic modules is encapsulation. In this production step, solar cells are encapsulated between a glass sheet and a polymer film as a backing sheet. Ethylene-vinyl acetate or EVA is commonly used for encapsulation. The curing behavior of EVA during the lamination process can be easily studied by DSC and DMA. The measurement results allow lamination conditions to be optimized and can be used for quality control purposes.

This slide describes the determination of the kinetics of the curing reaction of EVA employed in solar modules using the Model-Free-Kinetics evaluation program.

The method requires data from DSC measurements performed at three or more different dynamic heating rates as shown in the upper left part of the diagram.

The corresponding conversion curves shown below this were then calculated from the DSC curves and used to calculate the activation energy as a function of the degree of conversion or cure.

The activation energy curve is shown in the upper diagram on the right and enables the degree of cure to be predicted as a function of time under isothermal conditions. This is illustrated in the lower right diagram for a temperature of 135 degrees Celsius. The curve measured in a separate isothermal DSC experiment at the same temperature is shown in the same diagram. The measured and predicted curves agree very well.

Experiments like this are very useful for determining the optimum process parameters for the lamination of photovoltaic modules. Later on, we will discuss the curing of EVA using DMA.

Further information on this can be found in the article published in UserCom 31.

 

Slide 11: Application 3: DSC                                                    Composite

The next two slides show examples of the analysis of materials used for wind turbines.

In the wind power industry, the curing behavior and the glass transition temperatures of polymer matrices are important criteria for the composite materials used in the construction of wind turbines, for example for the rotor blades.

The correct degree of cure of rotor blades is crucial for their stability. Epoxy resins are used for the laminating process. They are cured in an isothermal curing step at a particular temperature.

For quality control reasons, the degree of cure of the rotor blades is usually measured afterward. If the glass transition and post-curing reaction overlap, it is not possible to reliably determine the degree of cure by conventional DSC. A solution to this problem is to use a temperature-modulated DSC method known as TOPEM. This method allows reversing and non-reversing effects like the glass transition and the curing reaction to be separated.

The slide shows the conventional DSC curve, as well as the total-, non-reversing-, and reversing-heat flow curves obtained from a TOPEM experiment. Using TOPEM we can easily calculate the enthalpy of the postcuring peak from the non-reversing heat flow curve and determine the glass transition temperature from the reversing heat flow curve. The results can be used for quality control purposes.

 

Slide 12: Application 4: DSC                                                    Epoxy resin

The second application deals with the isothermal curing of prepregs in the wind energy industry.

When curing is carried out at low isothermal temperatures, vitrification or glass formation can occur and the curing reaction stops. This results in incomplete curing of the material and could lead to the failure of final products. Information about vitrification is therefore important. This can be obtained by performing isothermal curing experiments on the epoxy resin using the TOPEM method mentioned before.

The slide shows measurements performed at 80 degrees Celsius. The upper curve is the quasi-static heat-capacity-curve and lower curve the total heat-flow-curve. The vitrification time is reached after about 86 minutes. Vitrification means that the epoxy sample becomes glassy and the curing process more or less stops. The material remains in the glassy state due to restricted molecular movement. Using TOPEM experiments, we can obtain information about the vitrification time of prepregs and finally determine the optimum curing conditions for the desired degree of cure.

 

Slide 13: Thermooptical Analysis (TOA)

The next method I want to describe is thermo-optical analysis or TOA for short.

TOA comprises a group of techniques that are used to measure optical properties of a sample as it is heated or cooled. The properties can be monitored by a DSC, an HPDSC or a Hot-stage system in combination with a microscope or a camera. The HPDSC instrument can also be connected to a chemiluminescence system. Some TOA instrumentation allows us to simultaneously measure calorimetric effects while visually observing the sample.

The table lists the most important applications of TOA for materials in the field of renewables, such as the determination of changes in morphology, shrinkage and crystallization behavior. In addition, thermochromism and oxidative stability can also be measured.

The picture shows a hot-stage cell set up for visual sample monitoring. When combined with a microscope and video camera, video images can be captured and overlaid with the temperature in real time.

The next slide shows an example of such an experiment.

 

Slide 14: Application TOA                    Crystallization behavior of biodiesel

Diesel fuel made from vegetable oil can be used in standard diesel engines and has several advantages over petroleum diesel fuel such as better lubricity.

The slide shows DSC measurement curves of samples of modified biodiesel and the determination of the wax-appearance-temperature in DSC cooling experiments. The wax-appearance-temperature defines the lowest temperature at which a product can be used without the risk of the fuel system becoming clogged with possible engine failure.

In this application, the crystallization behavior of three different biodiesel mixtures was investigated. The samples were cooled from plus 25 to minus 65 degrees Celsius (–65 °C) at 5 Kelvin per minute, held constant at minus 65 degrees (–65 °C) for 10 minutes, and then heated at the same rate.

The cooling or crystallization curves are shown overlaid in different colors in the upper part of the diagram, and the heating or melting curves in the lower part. The curves are all very similar. The main crystallization process occurs at about minus 44 degrees (–44 °C). However, some differences are apparent between zero and minus 25 degrees (–25 °C) where small amounts of material crystallize.

Microscopy was performed to study the crystallization process and obtain more information about differences in the crystallization process. The images show the samples at about minus 60 degrees (–60 °C). The microscopy results indicate clear differences in the morphology of the crystals.

In summary, we see that the combination of DSC and microscopy helps us to differentiate the three biodiesel samples.

 

Slide 15: Thermogravimetric Analysis (TGA)

Now let’s turn our attention to thermogravimetric analysis, or TGA.

In this technique, the mass of a sample is continuously measured as it is heated or cooled in a defined atmosphere. We simply put a few milligrams of the sample into a crucible, weigh the sample, heat it and record the weight change. From this, we can obtain information about the composition of the sample such as the polymer and filler content.

 

The schematic curve on the left shows a typical TGA measurement curve of a polymer composite material. Initially, before the heating ramp begins, the TGA measures the mass of the sample. At the end of the measurement, inorganic fillers like glass fibers remain behind as a residue after heating to temperatures of one thousand degrees Celsius (1000 °C). The steps due to loss of mass provide information about the composition of materials.

 

The steps are numbered next to the curve and explained in the table, namely:

One, heating begins and volatile components vaporize;

Two, pyrolysis of organic substances and polymers;

Three, at six hundred degrees Celsius (600 °C) the atmosphere is switched from nitrogen to air to obtain oxidative conditions;

Four, carbon black or carbon fibers burn;

Five, inorganic fillers such as glass fibers are left behind as a residue.

 

Slide 16: Thermogravimetric Analysis (TGA)

TGA is used to investigate processes such as vaporization or decomposition. Evolved gases can be analyzed online using hyphenated techniques such as TGA-MS, TGA-FTIR or TGA-GC/MS.

 

The table summarizes the main analytical applications of TGA for materials used in the field of renewable energy. The technique provides information about the composition of samples including their filler content. Furthermore, it allows us to check the thermal or oxidative stability of products such as biodiesel, or to analyze the content of moisture or volatiles in formulated products.

 

The picture on the right side is a view of the open furnace showing a sample holder with two positions for the sample and reference crucibles in a TGA instrument. The standard crucibles are made of alumina in order to withstand high temperatures.

 

Slide 17: Application 1: TGA/DSC                                             Corn cob

Biomass refers to renewable, non-fossil, organic substances from which energy can be obtained. Different kinds of biomass such as wood, straw, corn, sugar cane, eucalyptus, and oilseed rape are readily available and fast growing. Before biomass can be used as an energy resource, it has to be suitably treated. It can be gasified, liquefied or solidified. Several complex processes are available to do this.

This example describes how corn cob biomass was analyzed by TGA/DSC to simulate the pyrolysis of corn and in this way gain information about the potential of this particular biomass as a solid fuel.

In the diagram, the TGA mass loss curve is displayed in black and the DSC curve in red. The sample was heated at 10 Kelvin per minute in nitrogen up to 600 degrees Celsius. The atmosphere was then changed to air from 600 to 1000 degrees.

Analysis of the results gives us information about the composition of the corn cob. Initially, moisture is released, followed by volatiles and organic substances from 180 degrees onward. After pyrolysis, a solid material known as char amounting to about 23% of the initial mass is left behind. The residue after combustion of the char is the ash content. Fast growing biomass like corn can have an ash content of up to 20%.

The DSC curve gives us information about the heating or calorific value of the char. This enables us to classify the biomass with regard to the amount of energy it can supply.

 

Slide 18: Application 2: TGA/DSC-MS                                      Eucalyptus

The next example concerns eucalyptus biomass, which is transformed into fuel gas in a pyrolysis reaction. The eucalyptus biomass was investigated by TGA in combination with a mass spectrometer. In addition to obtaining information about the mass loss, this hyphenated technique allows us to identify the gases evolved in the pyrolysis process.

The dashed black TGA curve in the diagram shows the mass loss curve of the eucalyptus sample. The measurement was performed in a nitrogen atmosphere from room temperature to 600 degrees Celsius. The differently colored continuous curves show the mass spectrometric ion intensities for carbon dioxide, water, methane and hydrogen. These curves show the temperatures at which the gases are evolved and can also provide quantitative data after suitable calibration.

 

Slide 19: Application 3: TGA/DSC                                Lithium batteries

The next application example has to do with lithium batteries of which different types are available. In general, they have a high energy density and are used for portable electronic devices such as mobile phones and vacuum cleaners or in electric vehicles.

One problem associated with such batteries is that they may heat up during use. It is therefore important to test their temperature stability.

The slide shows the results of the TGA analysis of a sample of lithium-iron-phosphate (LiFePO4) a compound that is commonly used in lithium batteries. Lithium-iron-phosphate (LiFePO4) acts as the cathode material in the battery and offers advantages such as a longer lifetime and better power density compared with lithium-cobalt-oxide (LiCoO2).

The measurement curves shown in the diagram provide information about the thermal stability of lithium-iron-phosphate (LiFePO4). They indicate that the material is stable up to about 150 degrees Celsius.

 

Slide 20: Application 4: TGA/DSC                                Hydrogen storage

A major problem associated with renewable forms of energy is that the energy is not continuously available. To bridge gaps in supply, energy production from renewable energy sources requires intermediate storage systems. Hydrogen is a promising candidate for this because it can be stored as a gas, liquid or solid.

A safe and economical way to store hydrogen is to use a suitable solid, for example a metal hydride such as sodium-borohydride. Hydrogen can then be regenerated through the controlled addition of water with the formation of borate-hydrates. The different borate-hydrates release different amount of hydrogen.

The slide displays the TGA decomposition curve of a material used for hydrogen storage, a sodium-borate-hydrate consisting of a mixture of sodium-borate-tetra-hydrate and sodium-borate-dihydrate. The curve shows the stability ranges of the different hydrate forms.

This knowledge helps us to optimize the hydrolysis of sodium-borohydride. When it is used as storage medium to generate hydrogen through reaction with water, the degree of hydration of the sodium borate should be as low as possible in order to yield a high percentage of hydrogen.

Further information on this application can be found in the article published in UserCom 31.

 

Slide 21: Thermomechanical Analysis (TMA)

We now move on to thermomechanical analysis, or TMA. This technique measures the dimensional changes of a sample as it is heated or cooled.

The schematic curve on the left shows a typical TMA measurement curve of a polymer measured in compression using a small sample load. The different effects are numbered next to the curve and explained in the table, namely:

One, expansion below the glass transition;

Two, the glass transition point at which the rate of expansion changes;

Three, expansion above the glass transition; the steeper slope indicates a greater rate of expansion;

Four, softening with plastic deformation;

 

Slide 22: Thermomechanical Analysis (TMA)

The table summarizes the analytical applications of TMA for materials used in the field of renewable energy.

The main application is the determination of the expansion behavior and the Coefficient of Thermal Expansion, or CTE.

The technique is also excellent for determining the glass transition temperature, and for studying softening behavior, creep, or swelling in solvents. The picture on the right shows the typical experimental setup with a ball-point probe in contact with a sample specimen.

The following slide describes an application example.

 

Slide 23: Application 1: TMA                                       Battery membrane

This slide displays the TMA curve of a thin film used in lithium batteries as a membrane.

 

The membranes can become warm during use. This could lead to shrinkage and rupture and finally product failure. To make sure that this does not happen, the dimensional stability of the membranes must be investigated beforehand. This can be done by TMA.

 

The main diagram displays the TMA curve of the thin film measured in tension from room temperature to 200 degrees Celsius. The sample starts to shrink from 120 degrees onward and at higher temperatures shows two steps. This suggests the presence of a mixture of two different polymers, possibly polyethylene and polypropylene. Finally, the sample tears at about 200 degrees.

The small diagram in the lower left corner of the slide shows the low temperature region of the curve on a greatly expanded scale. The expansion and shrinkage of the sample is now clearly visible.

TMA provides information about the dimensional stability of materials. It helps us to check the quality of raw materials and detect the presence of polymer blends.

 

Slide 24: Dynamic Mechanical Analysis (DMA)

Dynamic mechanical analysis is a technique that is used to measure the mechanical properties of a viscoelastic material as a function of time, temperature and frequency when the material is deformed under a periodic oscillating stress.

 

The schematic diagram on the left shows the results of a DMA heating measurement of a shock-cooled semicrystalline polymer in the shear mode. The curves display the storage modulus, gee prime (G′), the loss modulus, gee double prime (G″),and tan delta as a function of temperature.

The different effects are numbered next to the curve and explained in the table, namely:

One, secondary relaxation, observed as a peak in tan delta;

Two, the glass transition, seen as a decrease in the storage modulus;

Three, cold crystallization begins with increasing temperature;

Four, recrystallization accompanied by a peak in tan delta;

Five, melting of the crystalline fraction with a decrease in the storage modulus;

 

Slide 25: Dynamic Mechanical Analysis (DMA)

The table lists the main analytical applications of DMA for materials used in the field of renewable energies.

In general, DMA provides information about the mechanical modulus, compliances, and about damping and viscoelastic behavior. The glass transition temperature, softening temperatures, or beta-relaxation processes are detected as peaks in tan-delta or through changes in the modulus.

The picture on the right shows a sample installed in the DMA ready for measurement in the bending mode.

 

Slide 26: Application 1: DMA               Curing measurements of EVA

This DMA application displays the results obtained from the curing of ethylene-vinyl acetate or EVA. As I mentioned earlier, this material is used for the encapsulation of photovoltaic modules. I also discussed how the curing kinetics can be measured by DSC.

The slide summarizes measurements of the curing of EVA using DMA in the temperature range minus 60 (–60 °C) to plus 180 degrees Celsius (+180 °C). In particular, we see the storage modulus curves of the first and second heating runs colored blue and red. The EVA sample was measured in shear mode at a frequency of 1 Hertz and a heating rate of 5 Kelvin per minute.

During the first heating run, the storage modulus begins to decrease at about minus 30 degrees (–30 °C) due to glass transition. This is followed by melting at 50 degrees. From 120 degrees onward, the modulus increases again due to the curing reaction because the modulus depends on the network density. The network formed makes the sample stiffer. The second heating run shows only the glass transition and melting but no postcuring reaction because the curing process is completed in the first heating run. Kinetic evaluations and predictions can also be made using DMA measurements.

Further details can be found in UserCom 31.                  

 

Slide 27: Summary

The table summarizes the most important events that can be used to characterize materials employed in the field of renewable energies as well as the techniques recommended for investigating the effects. A box marked red means that the technique is strongly recommended; a box marked blue indicates that the technique can also be used.

 

The most important effects that can be analyzed by DSC are the glass transition, melting behavior, and the enthalpy of cure.

 

TOA is the method of choice for the visual observation of samples, for example during crystallization and to detect cloud point effects.

 

The main applications of TGA are content analysis, thermal stability and evaporation behavior.

 

TMA can be used to characterize expansion, shrinkage or melting behavior.

 

DMA is a good method for characterizing the viscoelastic behavior of materials.

 

Slide 28: Summary

This slide presents an overview of the temperature ranges of the METTLER TOLEDO DSC, TOA, TGA, TMA, and DMA instruments.

 

In general, DSC experiments are performed at temperatures between minus one hundred and fifty degrees Celsius and plus seven hundred degrees. The temperature ranges may be different if special equipment or accessories are used.

TOA experiments can carried out between minus sixty degrees and plus three hundred and seventy five degrees. Several modes of operation are possible depending on the information required.

TGA measurements normally begin at room temperature. The maximum possible temperature is about sixteen hundred degrees.

TMA experiments can be performed between minus one hundred and fifty degrees Celsius and plus sixteen hundred degrees.

DMA samples are measured in the range minus one hundred and fifty degrees to plus five hundred degrees.          

 

Slide 29: For More Information

Finally, I would like to draw your attention to information about the use of thermal analysis in the field of renewable energies that you can download from the Internet.

METTLER TOLEDO publishes articles on thermal analysis and applications from different fields twice a year in UserCom, the well-known METTLER TOLEDO biannual technical customer magazine. Back issues can be downloaded as PDFs from the Internet as shown in the middle of the slide. A compilation of applications can be found in the “Thermal Analysis in Practice” handbook.

 

Slide 30: For More Information on Thermal Analysis

In addition, you can download details about webinars, application handbooks or information of a more general nature from the Internet addresses given on this slide.

 

Slide 31: Thank You

This concludes my presentation of thermal analysis in the field of renewable energy. Thank you very much for your interest and attention.

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