Differential thermal analysis (DTA) is a technique for identifying and quantitatively analyzing the chemical composition of substances by observing the thermal behaviour of a sample as it is heated. This technique is based on the fact that as a substance is heated, it undergoes reactions and phase changes that involve absorption or emission of heat. In DTA the temperature of the test material is measured relative to that of an sample inert material. A thermocouple imbedded in the test piece and another in the sample inert material are connected so that any differential temperatures generated during the heating cycle are graphically recorded as a series of peaks on a moving chart. The amount of heat involved and temperature at which these changes take place are characteristic of individual elements or compounds; identification of a substance, therefore, is accomplished by comparing DTA curves obtained from the unknown with those of known elements or compounds.
More popular today is Thermogravimetric analysis (TGA) which provides both mass loss and thermal information. TGA can provide information about physical phenomena, such as second-order phase transitions, including vaporization, sublimation, absorption, adsorption, and desorption.
Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature.
Dynamic mechanical analysis (DMA, also known as dynamic mechanical spectroscopy) is a technique used to study and characterize materials. It is most useful for studying the viscoelastic behavior of polymers.
| Parameter | Value |
|---|---|
| Mass of sample | up to 1 g |
| Ñalibrated weight | 1 g |
| Weighing range | from 0.250 g up to 1 g |
| Weight Resolution | 0.5·10-6 g |
| Temperature Resolution | 0.05 °C |
| DTA Resolution | 0.01 °Ñ |
| Atmosphere | air |
| Design | vertical |
| Temperature ranges | from 20 ° C up to 1100 ° C; from room temperature up to 1200 ° C |
| Heating speed | from 0,1 °Ñ/min up to 100 °Ñ/min |
Some typical problems wich can be solved using DTA technique:
DSC and TGA are often used for the analysis of pharmaceutical materials. DSC allows you to explore the changes occurring in polymorphic transformations at different heating rates. Thus, it may be determined heating rate required to provide polimorfonoy purity product (sometimes it is necessary to provide speeds of up to 750 ° C/min). TGA is often used to measure the remaining solvent and moisture, but can also be used to determine the solubility of pharmaceutical materials in solvents.
Thermoplastic polymers are used in packaging materials and household goods. For the study of materials phenomena, such as the impact of additives used in them (including color stabilizers and additives) and for the optimization pressing or extrusion processes DSC technique is used. For example - DSC for oxidation induction time to determine the amount of oxidation stabilizer present in thermoplastics (usually polyolefin). Analysis is often performed in synchronization with the TGA, which helps divide influence fillers, polymer resin and other additives. TGA can also give information on the thermal stability of the polymer and evaluate the effectiveness of additives (eg flame retardants).
Composite materials such as carbon fiber or glass epoxy composites are often investigated by DMA, allowing to measure the hardness of materials, to determine deformation module and damping (energy absorption). Space companies often use these analyzers with daily quality control to ensure that manufactured products meet specific specifications. Race car manufacturers in Formula 1 also have similar needs. DSC is used to determine the properties of curing resins used in composite materials, and can also confirm whether the resin can to be harden and allows to determine heat emission during hardening process. The application of analysis that predicts the kinetics can help adjust production processes. Another example is the application for TGA measurements of fibers in composites by heating the sample to the care of her pitches and determine weight loss.
The TGA analysis continuously weighs a sample as it is heated. As the result we receive TG-curves - sample weight changes versus of temperature or time. To interpret the results of the TG analysis it is necessary to process TG-curves. In particular, the derivative of the TG signal (rate of change of mass) allows to determine time or temperature at which the weight change occurs most rapidly.
The software allows you to build DTA (differential thermal analysis) and sample weight changes charts based on the input of text data received from sensor of corresponding equipment, to carry out mathematical processing - DTA curve smoothing, to determine the final weight of the sample point and temperature of phase transitions. Charts can be printed or saved as image files.
InterDTA v. 1.0 - software for processing and analyzing data received from deryvatografic analysis equipment:
Download user manual InterDTA v.1.0