Thermomechanical analysis (TMA) is a vertical dilatometry technique used to measure thermal expansion behavior and related properties (glass transition, crystal-crystal phase transition, sintering, softening, etc) of materials. It’s a powerful technique for materials science. TMA testing on polymers can shed light on processing conditions and use cases, as well as informing mechanical designs.
What Can TMA Testing on Polymers and Composites Help With?
1. Measuring the Coefficient of Thermal Expansion
A scientist sets up a TMA test.
An advantage of TMA over other contact based thermal expansion techniques is that the vertical arrangement of the expansion measurement avoids errors due to sagging or bending of the apparatus, and it allows extremely low forces to be used – which gives better and more accurate measurements on soft and rubbery materials. And, unlike optical techniques, no expensive optical table or sound cancellation is required. For this reason, TMA is the method of choice for measuring thermal expansion of polymers and polymer composites.
2. Measuring Anisotropy
Anisotropic behavior refers to behavior which has direction-dependent properties.
TMA can measure thermal expansion anisotropy directly and accurately in polymers and polymer composites. As many polymers and composites can be anisotropic because of their structure or manufacturing, the ability to measure the anisotropic thermal expansion behavior is critical to quality designs.
3. Determining Softening Temperature
Polymers and composites are often melt-processed, like in 3D printing.
With the penetration attachments available on TMAs, the softening point under different loads can be quickly and easily measured on the same apparatus as used for thermal expansion. This can in turn give information about how to process the material.
4. Measuring Glass Transition Temperature
Glass transition temperature is key to material performance in many industries, such as tires.
For thermoplastics, the glass transition temperature is key to the processing and use-cases of the material. Materials with low glass transition temperatures are rubbery and elastic at room temperature, making them useful for applications like sealants, rubber tires, balloons and anti-vibration pads. Using TMA, the glass transition temperature can be determined simultaneously with other properties of the material, like thermal expansion behavior.
5. Studying Thermal History Effects
Thermal history affects the mechanical behavior of polymers and composites. This means that by changing processing conditions, thermomechanical properties can be tuned.
Thermal history affects glass transition temperature, degree of crystallinity, and phase distribution. In other words, changing processing conditions – thus changing thermal history – can often change the properties of the end product. These effects are easily studied by TMA.
6. Studying Phase Behavior and Solid Transitions
Many polymers go through several solid phase transitions – such as a cold crystallization, crystal phase transitions, or glass transition, before the polymer actually melts. TMA can observe these events by looking at the change in the Coefficient of Thermal Expansion.
How Do You Get TMA testing?
Two options exist for getting TMA testing on your samples:
- Get contract testing at a commercial testing lab like Thermal Analysis Labs. This is a great option for groups with low sample volume or who aren’t sure if the data will shed light on their research problems. Learn more about contract TMA testing here.
- Bring equipment in-house and do it yourself. This is best for groups with the budget to support capital equipment, and who have a large enough volume of samples to make the instrument pay for itself. Contact one of our subject matter experts to learn more about our TMA products.
About the Author
|Written by Sarah Ackermann, MSc – Laboratory Services Manager, Thermal Analysis Labs|