Characterization of Thermosets by Means of Thermal Analysis
On Demand Webinar

Characterization of Thermosets by Thermal Analysis

On Demand Webinar

Thermal analysis is an excellent method for identification and characterization of thermosets

Thermosets are used for components that must be rigid, insoluble and of high mechanical strength and temperature stability. Production and processing are cheaper compared with metals. The four main techniques of thermal analysis, DSC, TGA, TMA, and DMA are ideal for characterizing such materials. The chief advantage is that properties can be measured as a function of temperature or time over a wide temperature range, from –150 to 1600 °C.

In this Webinar, we will show how thermal analysis is used to analyze thermosets and will present some typical examples of samples measured by DSC, TGA, TMA, or DMA.

39:23 min
English

The Webinar covers the following topics:

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

Thermal analysis is an excellent method for the identification and characterization of thermosets because their properties are strongly temperature dependent.

What is a thermoset?
Thermosets are polymers that can undergo a permanent chemical reaction known as curing to form a giant crosslinked network structure. They are also known as thermosetting polymers, resins or plastics. Fully cured themosets are rigid, typically insoluble solid materials of high mechanical strength and high temperature stability. In contrast to thermoplastics, thermosets cannot be melted and remolded to other shapes after curing.

Characterization of thermosets
Thermal analysis can be used to determine many of the key properties of thermosets. For example, an important application is the measurement of the glass transition and the curing reaction in epoxy resin systems.
The most important effects that can be analyzed by DSC are the glass transition, melting behavior, reaction enthalpies, curing, and thermal stability.
TMA is normally used to study the mechanical behavior of materials such as expansion, shrinkage, softening, and the glass transition.
DMA is the best method for characterizing the viscoelastic behavior of materials, the glass transition, and the frequency dependence of effects.
The main applications of TGA are compositional analysis, thermal stability and decomposition, and evaporation and desorption behavior.

This webinar discusses the most important thermal properties of thermosets and describes the thermal analysis techniques that can be used to measure them.

Thermal Analysis of Thermosets

Slide 0: Thermal Analysis of Thermosets

Ladies and Gentlemen,

Welcome to the METTLER TOLEDO webinar on the Thermal Analysis of Thermosets.

 

Thermosets are polymers that can undergo a permanent chemical reaction known as curing to form a giant crosslinked network structure. They are also known as thermosetting polymers, resins or plastics

Fully cured themosets are rigid, typically insoluble solid materials of high mechanical strength and high temperature stability. In contrast to thermoplastics, thermosets cannot be melted and remolded to other shapes after curing.

Thermal analysis is an excellent method for identifying and characterizing thermosetting materials and end-products because their properties are strongly temperature dependent.

 

The thermal analysis of thermoplastics and elastomers will be discussed in separate webinars.

 

Slide 1: Contents

This slide lists the main topics that will be covered in this webinar.

 

First, I want to discuss the most important thermal properties of thermosets and describe the thermal analysis techniques that can be used to measure them.

The techniques include:

Differential Scanning Calorimetry, or DSC,

Thermomechanical Analysis, or TMA,

Dynamic Mechanical Analysis, or DMA.

and Thermogravimetric Analysis, or TGA

I will then present a number of examples that illustrate how thermal analysis can be used to investigate the physical properties and behavior of thermosetting materials.

 

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

 

Slide 2: Introduction

The term “thermosetting resin” was originally used to describe liquid resins that become solid and hard on heating, in contrast to thermoplastics, which become soft and melt on heating.

Nowadays, the word “thermoset” is used generally for systems that irreversibly harden, irrespective of whether this is achieved through the action of heat, exposure to UV-light, or the addition of reactive components. In all these cases, an irreversible chemical curing reaction takes place.

 

The measurement curves on the right part of the slide illustrate the different thermal analysis techniques that can be used to measure and characterize thermosets; in this case, the thermoset was an epoxy resin powder known as KU600.

 

Slide 3: Introduction: Typical Properties

Thermal analysis can be used to determine many of the key properties of thermosets.

 

For example, an important application is the measurement of the glass transition and the curing reaction in epoxy resin systems.

The figure displays the DSC curing curve of a fresh resin, the postcuring curve of a partially cured resin, and the curve of the fully cured thermoset. The results show that as the degree of cure increases, the glass transition shifts to higher temperatures and the postcuring reaction enthalpy decreases. If the reaction enthalpy of the uncured resin is known, the degree of conversion can be calculated from the enthalpy of the postcuring reaction.

 

In general, thermosets are amorphous, that is, they do not melt but merely soften at the glass transition. This defines the upper temperature limit for their practical use.

 

Slide 4: Thermosets                                        Curing reaction

The schematic diagram illustrates the curing reaction. This is a complex polymerization process involving different reaction steps.

Thermosets are often identified at three stages of cure: A, B, and C.

The A-stage refers to unreacted mixtures of small reactive molecules, often monomers with two or more functional groups (1).

The reaction proceeds through linear growth and the branching of chains to partially reacted, increasingly viscous, and usually vitrified, B-stage material below the gel point (2).

On further heating, this devitrifies, undergoes further reaction and crosslinking (3), and can be processed to the completely cured C-stage thermoset (4).

 

Thermal analysis techniques can be used to obtain information about the reaction process such as the gel point, where the viscosity increases markedly, the pot-life or processing time, and the shelf-life which is related to the practical storage time of the thermosetting system.

 

Slide 5: 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.

 

The lower half of the slide illustrates the main events that occur when a sample is heated. These include initial melting, in which the sample changes from the solid to the liquid state followed by oxidation if the sample is exposed to air or oxygen, and finally decomposition.

Thermal analysis techniques can be used to measure properties such as the heat capacity, thermal expansion, mechanical modulus, softening, the change in sample mass and chemical stability to name just a few.

 

Slide 6: Thermal Analysis                                        Techniques

The slide shows the four most important thermal analysis techniques that are employed to characterize thermosets:

 

DSC allows you to determine the energy absorbed or released by a sample as it is heated, cooled or held at constant temperature.

The picture shows a DSC sensor with a crucible containing a sample, and a reference crucible.

TMA measures dimensional changes or the changes of mechanical behavior of a sample as a function of temperature

The picture shows the sample area with a quartz probe resting on the sample.

DMA measures the mechanical properties of a material as a function of time, temperature and frequency while it is subjected to a periodic stress.

The picture shows one of the several different sample-clamping assemblies.

Finally, TGA measures the mass of a sample as a function of temperature in a defined atmosphere.

The picture shows the unique METTLER TOLEDO ultra-micro balance with its automatic internal ring weights.

 

Slide 7: Industries and Applications

The table summarizes the extremely wide applications field of thermosets. They are used in practically all industries, ranging from automotive to medicinal.

.

One of the primary uses of thermosetting resins is as a matrix material in composites. Composites are nowadays widely used as high performance engineering materials in the automotive, aerospace, boat building, and other industries. Adhesives are another major application area. A large volume is also used in the coating industry, in electronic components, for wind power systems, and for sport goods.

 

Thermal analysis techniques are employed to measure thermal stability, determine glass transitions, for investigating the degree of cure to optimize processes, and for studying the mechanical behavior of materials.

Because the techniques are widely used in quality control, many of these analyses are defined in international standard methods.

 

Slide 8: DSC

Let’s begin with DSC.

This technique allows us to measure the amount of heat absorbed or released by a sample.

The standard METTLER TOLEDO DSC 1 instrument operates 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.

The schematic curve on the left shows a typical DSC measurement curve of a semicrystalline polymer. Exothermic effects point in the upward direction and endothermic effects downward. The effects are numbered next to the curve and explained in the table. These are:

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

Two, the evaporation of moisture;

Three, a glass transition of the amorphous fraction with enthalpy relaxation;

Four, chemical reaction (curing); and finally

Five, the beginning of oxidative exothermic decomposition.

 

Special instruments, allow you measure samples at higher or lower gas pressures, or at ultra-fast heating and cooling rates.

 

Slide 9: Differential Scanning Calorimetry (DSC)

The main analytical applications of DSC for thermosets are summarized in the table and have to do with the measurement of glass transitions, specific heat capacity curves, the enthalpy of reactions, reaction kinetics and thermal stability. This information can be used to identify polymers and define the working range of materials.

Furthermore, it can be employed in quality control and analysis of raw materials and to study the influence of additives. The measurement of reactions such as the curing reaction is an important application.

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

 

Slide 10: Application 1: DSC                                   Degree of cure

 

The first application demonstrates the relationship between the glass transition and the degree of cure. The experiments were performed using a two-component epoxy resin system consisting of DGEBA and DDM.

 

The diagram shows the DSC curing curve of a fresh sample and the postcuring curves of a series of samples that had been partially cured at one hundred degrees Celsius (100 °C) for different times to obtain different degrees of cure. After curing, the samples were rapidly cooled to minus forty degrees (–40 °C) before measurement.

The series of curves shows that with increasing curing time, the exothermic postcuring peak decreases, and the glass transition temperature increases. The glass transition temperature does not however exceed one hundred and twenty-five degrees (125 °C) because the sample vitrifies under these conditions.

Only curing at a higher temperature leads to complete crosslinking and the maximum possible glass transition temperature of one hundred and fifty-five degrees (155 °C). To achieve this, the thermosetting material has to be heated to at least one hundred and seventy degrees (170 °C).

 

The upper left inserted diagram shows the relationship between the degree of cure, alpha, and the glass transition temperature, Tg. This allows the degree of cure to be determined in a routine analysis from a measured value of Tg. The glass transition is therefore an important criterion for assessing the quality of a product.

 

Slide 11: Application 2: DSC                                   Postcuring

The top green curve displays the postcuring curve of a laminated composite material with a very high glass transition temperature recorded in a conventional DSC experiment. The postcuring reaction often begins at the glass transition when the mobility of the reactants increases. The effects due to the exothermic reaction and the change in heat capacity at the glass transition then overlap. This makes it difficult to determine the glass transition temperature and the postcuring enthalpy in a conventional DSC measurement.

This problem can be overcome by using a temperature-modulated DSC method known as TOPEM. This separates the two effects into reversing and non-reversing heat flow components. The reversing heat flow curve shows the change in the specific heat capacity due to the glass transition, and the non-reversing heat flow the enthalpy of the postcuring reaction. The sum of both heat flow components is the total heat flow.

 

Slide 12: Application 3: DSC Kinetics Evaluation (MFK)

This application has to do with reaction kinetics or the rate of reaction. The goal of such experiments is to be able to model and predict curing behavior.

The example shows how the reaction kinetics of a two-component resin used for constructional reinforcement elements can be described by model free kinetics (MFK) software.

 

The first step is to measure at least three dynamic DSC curves at different heating rates as shown in the upper left diagram. This data is then used to calculate conversion curves from which the activation energy of the reaction can be calculated as a function of conversion.

This allows the degree of cure to be predicted as a function of time, for example at forty-two degrees Celsius (42 °C) as shown in the lower half of the diagram.

To check the kinetic prediction, samples were first cured for different periods at forty-two degrees (42 °C). DSC postcuring measurements were then performed to determine the reaction conversions that had been attained. The results are shown by the blue stars and agree well with the predicted reaction curve. The postcuring curves showed that the resin system was still not completely cured even after more than 36 hours. This is due to vitrification of the resin.

 

Slide 13: Application 4: HPDSC Condensation Reaction

The diagram shows DSC curves of a phenolic resin measured in different crucibles.

 

The effects due to the endothermic vaporization of water produced in the polycondensation reaction of phenolic resins and the exothermic curing reaction often overlap. The curing peak is then no longer clearly defined and kinetic evaluation becomes impossible. The temperature range in which these two phenomena simultaneously occur is indicated by the arrow above the dashed curve.

If the curing reaction is measured in a high-pressure crucible, or in a high-pressure DSC instrument, the vaporization of the water is suppressed or shifted to higher temperatures. As a result, the effects due to curing and vaporization no longer overlap and the exothermic reaction can be properly recorded. The reaction peak free from effects due to vaporization is indicated by red asterisks.

 

Slide 14: Application 5: UV-DSC Photocalorimetry

The DSC photocalorimetry accessory allows you to characterize UV-curing systems. You can study photo-induced curing reactions and measure the influence of exposure time, light intensity and temperature on the rate of reaction and material properties.

 

The upper right inserted diagram shows a schematic view of the measuring cell of the METTLER TOLEDO DSC-Photocalorimetry System.

 

Both the sample and the reference sides are exposed to the same light intensity. This is done using a branched fiber-optic light guide. One end is connected to a suitable light source. The two exits are fixed in a holder and positioned directly above the sample and reference crucibles of the DSC. The holder can be mounted and demounted in about 2 minutes. This means that the DSC can be used for both photocalorimetric and for normal DSC measurements.

 

In this experiment, the sample was held constant at one hundred and thirty degrees Celsius (130 °C). After 6 minutes, the shutter of the light source was opened and the sample exposed to UV light for 15 minutes. The reaction shown by Curve 1 begins as soon as the light irradiates the sample and dies down after a certain time because the possible reactants have been used up, that is, undergone conversion.

If the fully converted sample is exposed to light again in the same way as before, no further reaction peak is observed. Curve 2 can therefore be used as a blank. The blank subtraction takes into account that a small amount of the absorbed light is converted to heat. This is the cause of the small step in the DSC curve at the beginning and the end of the measurement under UV light in Curves 1 and 2. The difference between the curves yields the net heat power of the crosslinking reaction.

The optimum conditions for a sample to achieve an adequate degree of crosslinking can then be determined by systematically varying the exposure parameters.

 

Slide 15: TMA/SDTA

Let’s now move on to thermomechanical analysis or TMA. This is a straightforward technique to measure mechanical properties of materials by measuring the dimensional changes of a sample as it is heated or cooled under a defined load.

 

The schematic curve shows a typical TMA measurement curve of a polymer under a small load. The different effects are numbered next to the curve and explained in the table. These are:

One, expansion below the glass transition;

Two, the glass transition point, indicated by a marked change in the rate of expansion;

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

Four, delamination;

Five, plastic deformation.

 

Slide 16: Thermomechanical Analysis (TMA)

The table lists the most important applications of TMA for thermosets such as the measurement of expansion behavior, contraction or softening phenomena, glass transition, gelation and swelling of material in a solvent.

The picture shows the sample mounted on a quartz support. The thickness is continuously measured by the TMA probe resting on the sample and yields the sample expansion as a function of temperature.

 

Slide 17: Application 1: TMA/SDTA                 Expansion Coefficient

In this experiment, the glass transition temperature, the coefficient of thermal expansion (CTE), and the delamination temperature of a printed circuit board (PCB) were determined in one single TMA measurement.

 

The PCB sample consisted of glass fiber with an epoxy matrix resin and flame retardant. The change in the slope of the TMA curve at about ninety-three degrees Celsius (93 °C) is due to the glass transition. As we can see, the CTE curve exhibits a large step in this region. The first irreversible change in the expansion curve at three hundred and twenty-three degrees Celsius (323 °C) indicates the beginning of delamination under the measurement conditions used.

 

Slide 18: Application 2: TMA/SDTA                         Time to gelation

This application shows how the viscosity of an adhesive increases with increasing conversion during isothermal curing. The material was initially in the liquid state but then reacted to form a solid.

 

The gel point is of major interest from the technical point of view. This is the point at which the adhesive becomes structurally stable. Gelation can be investigated by periodically raising and lowering the TMA probe out of and into the sample in an up-and-down movement. The probe is able to move freely until the resin gels and becomes rubbery-like. On further reaction, the sample hardens and the amplitude changes to a very small value. The reaction time at which the probe can no longer be lifted out of the sample is the gel point.

In the measurement shown, this is clear from the sharp decrease of the envelope difference curve after a reaction time of about 26 minutes.

 

Slide 19: Application 3: TMA/SDTA         Dynamic load TMA (DLTMA)

In the Dynamic Load TMA or for short, DLTMA mode, the force exerted on the sample alternates between a higher and a lower value at a fixed frequency.

DLTMA can be used to follow the crosslinking of a sample during curing. The method reacts very sensitively to changes in the elasticity of a sample and is therefore a good technique in quality control and damage analysis.

 

In this example, the three-point bending accessory was used for investigate a composite material. The ball-point probe touching the center of the sample exerted an oscillatory load that varied from zero point zero two (0.02) to zero point five Newtons (0.5 N) over a period of 12 seconds. The heating rate was ten Kelvin per minute (10 K/min).

The TMA software calculates the mean curve as well as the value of the Young’s modulus from the blank-corrected DLTMA curve. Glass transitions of highly filled polymers can be easily detected using 3-point bending due to the large change in modulus.

 

Slide 20: DMA/SDTA

Dynamic Mechanical Analysis or DMA measures the mechanical properties of viscoelastic materials as a function of time, temperature and frequency when the material is deformed under a periodic oscillating stress. The sample response is analyzed over a wide frequency range of up to 1000 Hz.

The modulus consists of two components; the storage modulus, emm prime (M′) and the loss modulus, emm double prime (M″). The storage modulus corresponds to the elastic behavior (the solid line) of the material whereas the loss modulus (the dashed line) is related to the viscous behavior of material.

Another useful quantity is tan delta, also known as the loss factor or damping factor. Tan delta is the ratio of the loss modulus and the storage modulus and is a measure of the amount of energy dissipated as heat during each deformation cycle.

 

The schematic diagram shows the results of a DMA measurement of a reactive resin. The curves display emm prime (M′) and emm double prime (M″) as a function of temperature.

The different effects are numbered next to the curve and explained in the table. These are:

One, the glassy state;

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

Three, viscous liquid;

Four, crosslinking;

Five, gel point;

Six, rubbery state

 

Several different clamping modes are available for DMA measurements, for example for shear, tension, and bending experiments. This mode used depends on the information required and the behavior and geometry of the sample.

 

Speaker:

NB In the above text, (M¢) is written phonetically as emm prime (M¢), etc. etc.

 

 

Slide 21: Dynamic Mechanical Analysis (DMA)

The table lists the main analytical applications of DMA for thermosets.

In general, DMA provides information about the mechanical modulus, compliances, damping properties and viscoelastic behavior as a function of frequency. The glass transition temperature is detected through changes in the modulus or as peaks in tan delta.

The most important DMA applications have to do with the determination of the glass transition and mechanical modulus of composites, and the determination of gel time.

 

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

 

Slide 22: Application 1: DMA                   Frequency dependence of Tg

The first DMA application displays the storage modulus and tan delta curves of a cured epoxy resin powder in the shear mode as a function of frequency and temperature.

The storage modulus curves, labeled gee prime (G¢) show a step change in the glass transition region whereas the tan delta curves display peaks. It can be seen that the peaks are shifted to higher temperatures at higher frequencies.

 

The glass transition is a relaxation effect. It has its origins in the molecular mobility of cooperative units. With increasing temperature, the frequency of the cooperative rearrangements increases. At low temperatures, the frequency of these rearrangements is much lower than the measurement frequencies used. In this case, the sample appears hard and the storage modulus is therefore large. At higher temperatures, the frequency of the cooperative rearrangements is much higher than the measurement frequency. The material then appears soft and has a low storage modulus.

 

Speaker:

NB In the above text, (G¢) is written phonetically as gee prime (G¢)

 

Slide 23: Application 2: DMA Curing

The second DMA application shows the curves obtained from the measurement of a two-component epoxy resin system in the shear mode. During curing, the modulus changes by more than six orders of magnitude. In the shear mode, the glass transition of the fresh and the cured resin as well as the gel point can be measured in one single experiment.

 

In the upper diagram, the glass transition of the uncured resin is shown by a marked decrease in the storage modulus, gee prime (G¢), at about –10 °C. In the liquid phase, gee prime is very low and cannot be measured. The loss modulus, gee double prime, (G″) starts to increase at about 120 °C due to curing, and the viscosity increases. The gel point corresponds to the temperature at which gee prime equals gee double prime, in this case at about 150 °C. The glass transition of the cured material can be determined in a cooling experiment.

 

The viscosity curve of the liquid sample shown in the lower diagram was calculated from the loss modulus.

 

Speaker:

NB In the above text, (G¢) is written phonetically as gee prime (G¢), etc.

 

 

Slide 24: Thermogravimetric Analysis (TGA) 1

The final technique I want to discuss is Thermogravimetric Analysis or TGA.

In TGA, the mass of a sample is continuously measured as it is heated or cooled in a defined atmosphere.

The schematic curve shows a typical TGA measurement curve of a polymer. The steps due to loss of mass provide valuable information about the composition of materials.

 

The steps are numbered next to the curve and explained in the table. These are:

One, heating begins and volatile components vaporize;

Two, pyrolysis of the polymer under inert conditions;

At six hundred degrees Celsius (600 °C) the atmosphere is switched from nitrogen to oxygen to obtain oxidative conditions;

Three, carbon black or carbon fibers burn;

Four, a residue of inorganic substances remains.

 

The large step indicated by step two is the main pyrolysis of the polymer. This step can be used to determine the amount of a particular component. The temperature at which the step occurs is characteristic for the type of polymer investigated.

 

Slide 25: Thermogravimetric Analysis (TGA) 2

TGA is used to investigate processes such as vaporization or decomposition. Evolved gases, for example from condensation reactions, can be analyzed online using hyphenated techniques such as TGA-MS or TGA-FTIR.

 

The table summarizes the main analytical applications of TGA for thermosetting materials. The technique provides information about the composition of samples including their fiber or filler content. Furthermore, it allows us to check the thermal or oxidative stability of products or analyze the content of moisture or volatiles in products.

 

The picture on the right side displays a view of the open furnace, a sample holder with two positions for the sample and reference crucibles in a TGA instrument. The standard crucibles are made of alumina.

 

Slide 26: Application 1: TGA/DSC                   Compositional analysis

The first TGA application shows the measurement of an epoxy powder and illustrates how compositional analysis is performed

Approximately 15 mg of a sample was heated from room temperature to six hundred degrees Celsius (600 °C) under nitrogen and then from six hundred (600) to eight hundred and fifty degrees (850 °C) under air. The TGA curve exhibits two steps. The first step, between three hundred and twenty (320) and four hundred and eighty degrees (480 °C), corresponds to decomposition of the polymer through pyrolysis. The step height is proportional to the polymer content and is normally expressed as a percentage. The carbon present burns on switching to air.

 

The DTG curve is the first derivative of the TGA curve. In this case, it helps us to determine the optimum limits for the step evaluations. The two main steps are thus observed as large DTG peaks.

 

METTLER TOLEDO TGA instruments simultaneously measure the mass loss and the DSC heat flow signal of the same sample. The DSC curve provides additional information that can be used to identify thermal events. The combustion of carbon on switching to air produces a large exothermic effect which is shown as a large DSC peak. In contrast, pyrolysis of the resin exhibits only a small endothermic effect.

The TGA and DTG curves alone do not show the glass transition or the exothermic curing reaction. These thermal events are however observed in the DSC curve at about 70 and two hundred degrees Celsius (200 °C) respectively. The DSC signal clearly provides very useful complementary information.

 

Slide 27: Application 2: TGA/DSC                   Decomposition products

In this application, a hyphenated technique consisting of a mass spectrometer connected on-line to a TGA instrument was used to analyze volatile decomposition products from a printed circuit board.

The mass spectrometer (MS) allows volatile decomposition products evolved from the sample in the TGA to be qualitatively and quantitatively analyzed. Compounds with a sufficiently high vapor pressure pass from the TGA into the MS where the fragment ions are analyzed according to their mass-to-charge ratio.

 

The upper diagram shows the TGA and DTG curves. These exhibit a large one-step mass loss around 30%. The mass spectra of the evolved gases exhibit fragments with mass-to-charge ratios of isotopes that can be easily assigned to bromine. The curve in the lower diagram displays the ion current of bromine with a mass-to-charge ratio of 79. This ion current curve shows that decomposition products containing bromine are evolved in the decomposition step.

 

Slide 28: Summary 1

The table lists the chief events and properties that characterize thermosetting materials and the thermal analysis techniques recommended for their analysis. A red box denotes the recommended technique; a blue box indicates that the technique can also be used as an alternative.

 

The most important effects that can be analyzed by DSC are the glass transition, melting behavior, reaction enthalpies, curing, and thermal stability.

TMA is normally used to study the mechanical behavior of materials such as expansion, shrinkage, softening, and the glass transition.

DMA is the best method for characterizing the viscoelastic behavior of materials, the glass transition, and the frequency dependence of effects.

The main applications of TGA are compositional analysis, thermal stability and decomposition, and evaporation and desorption behavior.

 

Slide 29: Summary 2

This slide summarizes the temperature ranges of the METTLER TOLEDO DSC, TMA, DMA, and TGA instruments

 

In general, DSC experiments are performed at temperatures between minus one hundred and fifty degrees Celsius (–150 °C) and plus seven hundred degrees (700 °C). If special equipment or accessories are used, the temperature ranges, and heating and cooling rates may be different.

TMA experiments can be performed between minus one hundred and fifty degrees (–150 °C) and plus eleven hundred degrees (1100 °C). Several modes of operation are possible depending on the information required

DMA samples are measured in the range minus one hundred and fifty degrees (–150 °C) to plus six hundred degrees (600 °C). A number of different clamps are available for measuring samples in the shear, bending, tension and cantilever modes.

TGA measurements normally begin at room temperature. The maximum possible temperature is about sixteen hundred degrees (1600 °C). A combination of different furnace sizes and sensors is available. In addition to automatic operation, the instrument can be connected to vacuum, sorption, FTIR and mass spectrometer systems.

 

Slide 30: For More information on Thermosets

 

Finally, I would like to draw your attention to information about the analysis of thermosets 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 from www.mt.com/TA-usercoms.

 

A large collection of applications can be found in the “Thermosets” and the “Thermal Analysis in Practice” handbooks.

 

 

Slide 31: For more information on Thermal Analysis

 

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

 

 

Slide 32: Thank you

 

This concludes my presentation on the thermal analysis of thermosets. Thank you very much for your interest and attention.

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