Spring is upon us, and with it comes fluctuating weather conditions! You’re enjoying some warmer days, but also a little worried how the extreme changes in temperature may affect your products. Thermal analysis can help you better understand how your materials fare with the changes in temperature. But with so many options in the market, how do you choose?
Today we’ll take a quick look at two most commonly used techniques for thermal analysis: Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC).
What can TGA tell us?
Thermogravimetric Analysis can track the changes in the mass of your sample as the temperature is changed in a controlled manner. Analysis typically consists of monitoring the mass of your sample while heating at a constant rate, or held at a constant temperature over time.
With the Netzsch TG 209 F3 Tarsus, we can probe changes in the sample mass from room temperature up to 1,000°C. Within this range, several changes can occur that would result in a mass loss. For example, loss of solvent or moisture through evaporation and/or boiling, and thermal decomposition (also called pyrolysis when completed in an inert environment). As such, TGA is often used for compositional analysis, e.g. moisture content, organic content, filler content, ash content, etc. It is particularly useful in this regard for samples with characteristic decomposition steps, such as calcium carbonate. However, mass gains may also be observed, especially under an oxidizing environment.
What can the DSC tell us?
Differential Scanning Calorimetry can track the changes in the heat flow to and from a sample as the temperature is changed in a controlled manner. The sample may be subjected to some heating and cooling cycle(s) in an inert or oxidizing environment. Each of these cycles may provide different information. For example, the initial heating cycle can provide insights into the sample’s thermal history (behavior dictated by how the samples have been produced and stored), which might be critical for failure analysis of plastic or rubber parts. Once the thermal history has been eliminated, the true properties of the components can be revealed in the second heating cycle.
With our recent upgrade to the Netzsch DSC 214 Nevio, we can probe changes in the sample from -170°C to 600°C. Within this range, several changes can occur that would result in a change in energy. For example, solid-liquid phase transition (melting or fusion; conversely, freezing or crystallization), solid-solid transition (cold crystallization from amorphous to crystalline phases, or changes between different polymorphs), glass transition (changes in amorphous materials between brittle, glassy state and flexible rubbery state).
While the hardware upgrade for DSC is expected to deliver higher performance and reproducibility, the updated Proteus software also provides many new features at Particle Technology Labs. These features include possible compositional identification by comparison of the thermal curves against a vast library of known materials, or a smaller custom-built library of reference materials as needed. Additionally, the software is fully compliant with requirements of 21 CFR Part 11, which is important for pharmaceutical, food and cosmetic products.
When do I need TGA vs. DSC?
The answer may be both! Very broadly speaking, if your sample might generate a lot of gas in the temperature range of interest (e.g. thermal decomposition), then TGA would likely be more suitable. If you are more interested in the temperature and energy related to an endothermic or exothermic transition, then DSC would be more appropriate. If the thermal properties of your samples are not well known, both analyses might provide useful information.
Both techniques can be applied to wide ranging types of materials from pharmaceuticals ingredients and finished products, plastics, metals, ceramics, petrochemical, and advanced materials.
Some differences and similarities between the two techniques are highlighted in the table below.
|Primary Determination||Changes in the sample mass as a function of temperature or time||Changes in the heat flow to and from the sample as a function of temperature or time|
|Temperature Range||Room temperature to 1,000°C||-170°C to 600°C|
|Heating Rate||0.001°C/min to 200°C/min||0.001°C/min to 500°C/min|
|Cooling Rate||N/A (not controlled)||0.001°C/min to 500°C/min|
|Resolution||0.1 µg||0.25 μW|
|Analysis Environment||Inert (nitrogen flow),
or oxidizing (air flow)
|Inert (nitrogen flow),
or oxidizing (air flow)
|Sample Amount||Approximately 5-50 mg||Approximately 5-50 mg|
|Typical Output||· % by mass lost or gained
· residual mass
|· Transition temperature (e.g. onset, peak)
· Transition enthalpy
|Example of Applications||· Moisture content
· Thermal stability
· Compositional analysis
|· Phase transitions, e.g. melting (fusion), crystallization
· Glass transition
· Solid-solid transitions, e.g. polymorphism, cold crystallization
· Concentration analysis (with known standards)
· Specific heat
· Oxidative induction time and temperature (OIT)
Why Choose Particle Technology Labs?
Particle Technology Labs is a fully independent, cGMP compliant and ISO accredited laboratory. Our lab has nearly 30 years of experience in the particle characterization field. Developing an appropriate analytical procedure for thermal analysis is paramount in obtaining the appropriate information for your needs. Additionally, understanding what processes correspond to each change in sample mass typically requires some knowledge of general chemistry and sample properties. The experts at Particle Technology Labs can guide you through the entire process from selecting the best options for your needs, conducting the analysis under suitable conditions, ensuring compliance when needed, and assisting with data interpretation.
By Chorthip Peeraphatdit – Particle Characterization Chemist IV / Team Leader