Thermoanalytical Methods Review: TGA and EGA

The sample holder and furnace must not be in contact. There are 3 main possibilities to place the sample relative to the balance and furnace.

The PC is incorporated into most commercially available instruments to control heating and cooling cycles, store data, and handle data. It also helps resolve overlapping thermal reactions.

The 1st derivative of the Dm vs.T (DTG) curve is used to resolve overlapping thermal reactions. It is used when there are multiple thermal reactions occurring simultaneously.

The different types of water are bulk water, absorbed water, and constitutional water. They are differentiated by their expulsion temperatures.

The water/moisture content is calculated using the formula: (D/A) × 100%. Where D is the mass loss and A is the initial mass.

The rate of mass change (dm/dt = f(T))

It corresponds to a point of inflection in the TG curve, where mass is lost (or gained) more rapidly.

It provides a better distinction of overlapped steps

They correspond to the loss of water molecules (2 H2O, 2 H2O, and 1 H2O) at specific temperatures (75°C, 113°C, and 250°C)

It is proportional to the mass change

To measure the amount of moisture and volatiles present in the sample.

To burn the carbon and measure the carbon and ash content.

It allows for the preparation of multiple samples at the same time and enables overnight or weekend measurements.

To analyze the gases evolved during the thermogravimetry analysis.

To prevent the loss of moisture or absorption of water, which can affect the accuracy of the results.

The primary purpose of EGA is to identify and analyze the gases evolved during thermal decomposition, which correlates with TGA data by providing additional information on the chemical composition of the gases released.

The peak of the DTG curve represents the maximum rate of weight loss, providing information on the temperature and rate of thermal decomposition.

Water content analysis in TGA is significant in understanding the moisture content of materials, which is affected by heating rates that can influence the accuracy of water content measurements.

The principle behind TGA is to measure the weight change of a sample as a function of temperature, providing information on thermal decomposition, phase transitions, and moisture content.

The DTG curve represents the rate of weight change, providing information on the thermal decomposition rates and temperatures, which correlates with the TG curve to provide a comprehensive understanding of thermal decomposition.

To prevent contamination or loss of sample during storage and handling prior to measurement.

Loss of mass (vapor emission) or gain of mass (gas fixation)

It allows for the detection of the type of gas evolved during decomposition or desorption of a heated sample.

Balance, thermobalance, furnace, sample chamber, instrument control/data handling

It enables the simultaneous analysis of both the weight change and the evolved gases during a thermogravimetric experiment.

To determine the decomposition behavior of the sample

To identify the gases evolved during the decomposition process

It provides a more detailed analysis of the thermal decomposition process by highlighting the rate of weight change.

By measuring the weight loss corresponding to the evaporation of water or moisture.

The rate of change of mass with respect to temperature

The primary principle of thermogravimetry is the measurement of the variation in mass of a sample as a function of temperature or time in a controlled atmosphere. It is used to analyze materials by providing information on decomposition, oxidation, and other thermal reactions.

The DTG curve provides information on the rate of mass change with respect to temperature or time, allowing for the identification of reaction peaks and kinetic analysis.

Evolved gas analysis (EGA) is a technique used to analyze the gases evolved during a thermogravimetric experiment. It is used to identify and quantify the gases produced during thermal decomposition or reaction.

Moisture content is an important parameter in materials science, affecting material properties and stability. Thermogravimetry can be used to analyze moisture content by measuring the mass loss associated with water evaporation.

Thermogravimetry has applications in materials characterization, quality control, process control, and decomposition analysis in fields such as polymers, pharmaceuticals, and ceramics.

The atmosphere used in thermogravimetry can significantly affect the results, as it can influence the thermal behavior of the material, such as oxidation or decomposition reactions.

The temperature range is critical in thermogravimetry, as it determines the thermal events that are observed. The selection of the temperature range depends on the material and the desired information.

Thermogravimetry provides valuable information on material properties, such as thermal stability, decomposition, and moisture content, making it a powerful tool for materials characterization.

Thermogravimetry measures the change in mass of a sample as a function of temperature, whereas DSC measures the heat flow. TGA is particularly useful for analyzing materials with significant mass changes during thermal events.

Sample preparation is critical in thermogravimetry, as the sample must be representative of the material and free from contamination. Improper sample preparation can lead to inaccurate results.

The primary difference is that thermogravimetry measures mass changes, whereas other techniques measure other properties such as heat flow or dimensions.

Simultaneous measurements provide a more comprehensive understanding of the sample by allowing for the measurement of multiple properties at once.

The atmosphere affects the results of the analysis, and can be controlled to simulate different conditions.

Computer-controlled instruments provide data processing and sample handling capabilities, allowing for more efficient and accurate analysis.

Thermogravimetry can determine sample purity by measuring the mass changes associated with impurities.

Thermogravimetry is a subgroup of thermal analysis techniques, which study the properties of a sample as a function of temperature.

Thermal analysis is used to understand the thermal properties of materials and their behavior under different conditions.

The primary principle is that the mass of the sample changes as a function of temperature.

The temperature program determines the conditions under which the sample is analyzed, and can be tailored to simulate different scenarios.

Evolved gas analysis is used to identify and quantify the gases produced during thermogravimetric analysis.

The primary function of the furnace is to heat the sample to a controlled temperature, usually in a specific range, depending on the material used.

The sample chamber is where the sample is placed, and it is designed to ensure that there is no contact between the sample holder and the furnace.

The type of pan used can affect the results of a thermogravimetry analysis, as it can influence the sample's heating rate and the accuracy of the mass measurements.

The null-point weighing balance ensures that the sample remains in the same heating zone, allowing for accurate mass measurements.

The advantage of using an isothermal or quasi-isothermal technique is that it allows for the resolution of overlapping thermal reactions, providing more accurate results.

The DTG curve provides the rate of mass change at any temperature, with the height of the peak curve representing the rate of mass change.

The ceramic crucibles are used to store the samples, and the lid is removed just before the experiment, allowing for accurate measurements.

Minimizing the exposure of thermogravimetry samples to air is important to prevent loss of moisture or absorption of water, which can affect the results.

The PC is used to store data and monitor heating and cooling cycles, providing a digital platform for data analysis and processing.

Electrostatic effects can affect the results of a thermogravimetry analysis, as they can influence the sample's mass measurements.

To provide a baseline or a standard against which the sample can be compared, and to ensure accurate measurements.

TD measures thermal expansion without an external load or stress, while TMA measures changes in dimension of a material when the temperature changes, with or without an external load or stress.

It represents the material's ability to store energy when deformed, and is associated with the elastic behaviour of the material.

To change the properties of the polymer, such as lowering its glass transition temperature.

Joules per second (J/s), which is equivalent to Watts.

TMA measures dimensional changes under a constant load, while DMA measures the response of a material to a dynamic load.

Because they have a similar thermal expansion to the sample being tested, and do not undergo thermal transitions.

It helps understand how materials behave under different conditions like temperature and frequency, and provides information on both elastic and viscous behaviour.

It represents the energy absorbed or released by the sample as it is heated or cooled.

To ensure that the deformation and stress are accurately transmitted to the material.

It increases the free volume, allowing polymer chains to slide past each other more easily, thereby lowering the glass transition temperature.

It decreases.

Rubbery-elastic state.

To detect transitions that are missed in conventional DSC systems.

From -180°C to 600°C.

Reduced analysis time and high throughput.

To enable true isothermal measurements.

It provides accurate specific heat analysis.

It increases.

To make them easier to work with and more suitable for specific uses.

Sample size and packing, heating rate, type of pan used in the instrument, gas flow, electrostatic effects, condensation and reaction, buoyancy, sample holder, and reaction enthalpy.

Samples are airtight sealed, and the lid is pierced just before measurements are taken. They are stored in ceramic crucibles, and the lid is removed just before the experiments.

DTA measures the temperature difference against a reference sample, while DSC measures the difference in heating power needed on a sample.

TMA measures changes in the dimension of a material when the temperature changes and when the level of stress on the material changes.

Storage modulus (E') and loss modulus (E''), representing the material's ability to store energy when deformed and the material's ability to dissipate energy as heat, respectively.

Plasticizers modify the properties of amorphous materials (i.e., polymers) by decreasing the glass transition temperature with increasing plasticizer content, making the material more rubbery-elastic.

Hyper DSC uses two small, low-mass furnaces to heat and cool rapidly, providing better resolution and higher sensitivity, enabling the detection of transitions missed in conventional DSC systems.

EGA is used to study the gas evolved from a heated sample undergoing decomposition/desorption.

Plasticizers decrease the glass transition temperature with increasing plasticizer content, making the material more rubbery-elastic.

DMA studies how materials respond to forces (stress) and stretching (strain) in a dynamic and changing way.

Thermal analysis is a group of techniques in which a property of the sample is monitored against time or temperature while the temperature of the sample is programmed. The main variable being monitored is the property of the sample, such as mass, volatiles, temperature, heat, or heat flux, etc.

The properties that can be monitored include mass, volatiles, temperature, heat or heat flux, dimensions, acoustical properties, electrical properties, magnetic properties, optical properties, and radioactive decay.

TG determines sample purity, decomposition behavior, and chemical kinetics by measuring the changes in the mass of the sample as a function of temperature or time in a controlled atmosphere.

The essential components include the balance and furnace (thermobalance), sample chamber, and instrument to control data handling.

The primary purpose of TG analysis is to determine sample purity, decomposition behavior, and chemical kinetics.

DSC is a technique that measures the heat or heat flux of a sample as a function of temperature or time in a controlled atmosphere.

Thermogravimetry (TG), Evolved Gas Analysis (EGA), Differential Thermal Analysis (DTA), Differential Scanning Calorimetry (DSC), Thermodilatometry (TD), Thermomechanical Analysis (TMA), Dynamic Mechanical Analysis (DMA), Thermosonimetry, Thermoacoustimetry, Thermoelectrometry, Thermomagnetometry, and Thermooptometry are some of the thermal analysis techniques used.

EGA is used to analyze the gases that are evolved during a thermogravimetry analysis, providing information about the decomposition behavior of a sample.

The primary purpose of TD is to measure the changes in the dimensions of a sample as a function of temperature or time in a controlled atmosphere.

DMA is used to measure the mechanical properties of a sample as a function of temperature or time in a controlled atmosphere, providing information about the viscoelastic behavior of a sample.