Fillers, Stability, and Volatiles
Plastic and rubber materials that are used in commercial applications always contain multiple ingredients to achieve a balance of cost, performance, and processability. It can be important to verify the composition of materials as part of a quality control (QC) or quality assurance (QA) project. Or, comparative analysis of materials from different suppliers, production facilities, or time periods may be needed. In these cases, thermogravimetric analysis can be a powerful analytical tool.
Thermogravimetric analysis (TGA) operates on a simple principle; heat a sample in a controlled atmosphere using a controlled heating rate and monitor the change in mass as a function of time and temperature. Most samples will lose weight when they are heated because water or solvents are released during the initial portion of the heating profile. At higher temperatures liquid additives and process aids may begin to evaporate. Plastic and rubber ingredients will decompose and vaporize at even higher temperatures leaving inorganic fillers, ash, or carbon residue.
The TGA method is quantitative and is especially useful for comparing materials. The output from the instrument is a plot of mass as a function of time and temperature. Usually, the mass is converted to "% initial mass remaining" so that samples having different mass values can be directly compared.
To compare the basic composition of materials for any reason, consider using thermogravimetric analysis as a rapid, sensitive, and inexpensive method of analysis. TGA can provide excellent baseline data for your materials.
If you want more information about the TGA method,
click on the link below.
> Read more about Thermogravimetric Analysis (TGA)
An important feature of plastic and rubber materials is that the molecular structure allows for various levels of organization or crystallinity. Two fundamental transitions that are recorded for polymer materials are the glass transition temperature and the melting region.
These thermal transitions have significant influences on the end-use performance of materials. In fact, the balance of amorphous and crystalline features often determines the suitability of a specific polymer material for an application. And, as a polymeric material ages, the relative amount of crystallinity can change. Increased crystallinity can result in shrinkage, cracking, reduced impact resistance, and harder materials.
Differential scanning calorimetry (DSC) can readily document the glass transition temperature of materials and the temperature region over which melting will occur. These basic parameters are important for setting end-use temperature limits and also have a strong effect on the required process temperatures.
DSC instruments can operate in a conventional heating mode where typically a linear modest heating rate is employed. Alternatively, to isolate overlapping thermal transitions, one can employ a modulated DSC (MDSC) technique. The MDSC method superimposes a sinusoidal heating-cooling profile onto the standard linear heating profile. Some specialized applications may benefit from rapid heat-cool (RHC) DSC wherein heating rates in excess of 200 °C per minute are imposed on the sample.
If you want more information about the DSC method, click on the link below.
> Read more about Differential Scanning Calorimetry (DSC)
In this issue:
We bring you thermal analysis information in this issue to answer important questions about how plastic and rubber materials respond to temperature. Fillers, stability, and volatiles are analyzed using thermogravimetric analysis (TGA). Thermal transitions are evaluated using differential scanning calorimetry (DSC). Frequency response of materials is assessed using dynamic mechanical analysis (DMA). TGA, DSC, and DMA instruments are three of the tools found in a well-equipped thermal analysis laboratory.
Browse through this e-Newsletter for information about;
- Thermogravimetric Analysis (TGA)
- Differential Scanning Calorimetry (DSC)
- Dynamic Mechanical Analysis (DMA)
You can get even more information about these important analytical methods by visiting our web-site or by talking to one of our experts.
Also in this e-Newsletter is the very popular section, Jay’s Cool Microscopy Pics of the Month!
Frequency Response of Materials
Many plastic and rubber materials do not enjoy a static existence. Instead, they are subjected to oscillatory or vibratory forces. How will your plastic or rubber material respond to oscillatory forces?
Dynamic mechanical analysis (DMA) is the analytical tool of choice when you want critical information about the response of your materials to changes in frequency and temperature. Modern DMA instruments allow us to directly determine the physical properties of samples from -120 °C to over 300 °C.
The usual outputs from the instrumentation are loss modulus, storage modulus, and the ratio of these two properties which is called the loss factor, the loss tangent, or tangent delta (Tan δ)
In addition to the direct evaluation of materials over a broad frequency range modern software coupled with fundamental principles of polymer science allow properties at lower (creep) and higher (impact) frequencies to be modeled.
As a result, DMA is a powerful, multi-dimensional characterization tool for plastic and rubber materials.
If you want to read more about the Dynamic Mechanical Analysis (DMA) method, click on the link below.
> Read more about Dynamic Mechanical Analysis (DMA)