By Arya Hakimian, Application Scientist
When it comes to measuring thermal conductivity, there’s no one-size-fits-all solution. Each method, whether steady-state or transient, has its own advantages and limitations. Choosing the correct technique depends on several factors: the type and format of the sample, the required testing standard (ASTM or ISO), and practical considerations like test time, temperature range, and ease of sample preparation.
Among transient methods, two approaches often compared are the Modified Transient Plane Source (MTPS) and the Single-Sided Transient Plane Source (TPS), sometimes even referred to as a “modified” or “mTPS”. While they may sound similar, they differ significantly in design, performance, and application.
MTPS vs TPS: A High-Level Comparison
The MTPS method, patented by C-Therm Technologies, is standardized under ASTM D7984 for textiles’ effusivity characterization and is also widely used in industries including automotive, aerospace, and electronics. In contrast, the TPS method, including its single-sided variant, is standardized under ISO 22007-2 and ISO 22007-7, respectively, and is non-proprietary.
Here’s how they compare:
- Sensor Design: MTPS uses a patented guard ring to ensure one-dimensional heat flow, providing a truly directionally dependent measurement. TPS sensors, which do not have a guard ring, lack this control and average over a broader area.
- Accuracy: MTPS typically achieves <5% error, while single-sided TPS can exceed 10%[1].
- Thermal Conductivity Range: MTPS can measure as low as 0.01 W/mK, whereas single-sided TPS is limited to materials above 1.0 W/mK1.
- Test Time: MTPS delivers results in under 3 seconds; TPS can take up to 300 seconds.
- Setup and Operation: MTPS requires minimal prep and is less prone to operator influence due to its optimized calibration settings. TPS, on the other hand, demands a more involved setup with operator oversight during test parameter design and data analysis.
What Is the Single-Sided or “mTPS”?
The single-sided TPS is an adaptation of the traditional double-sided TPS method. It uses an insulative backing to simulate one-sided contact, but this introduces several limitations:
- It’s not a true single-sided sensor and lacks directional control as it does not contain a guard ring.
- It struggles with low-conductivity materials and is best suited for rigid, high-conductivity samples.
- It requires compression during testing, which can distort soft or compressible materials.
- It does not conform to ASTM D7984, unlike C-Therm’s MTPS.
Use Cases and Limitations
MTPS is ideal for:
- Low and high conductivity materials and non-solids such as liquids, powders and pastes
- Thermal mapping of filled materials, which is highly relevant to the development and optimization of Thermal interface materials (TIMs) and polymer composites
- Applications requiring ASTM compliance and fast, repeatable results
Single-Sided TPS is better suited for:
- Rigid, high-conductivity samples
- Scenarios where contact agents are undesirable
- Labs with experience in handling complex sample prep, analysis and longer test cycles
- Product certification testing and technical data sheet validation requiring the ISO standard
Both the MTPS and single-sided TPS sensors are available on C-Therm’s Trident platform, giving users the flexibility to select the best method for their specific testing needs.
Conclusion
While both MTPS and single-sided TPS have their place in thermal conductivity testing, MTPS offers a more robust, accurate, and user-friendly solution, especially for materials with low thermal conductivity or where ASTM compliance is required. Its patented design, minimal sample prep, and rapid test time make it a preferred choice for many industrial and research applications.
About Us:
C-Therm Technologies Ltd. is the global leader in thermal conductivity testing instrumentation. Headquartered in Fredericton, New Brunswick, Canada, C-Therm specializes in non-destructive thermal analysis solutions that empower researchers, manufacturers, and quality control professionals across a wide range of industries – from aerospace and automotive to textiles, electronics, and energy storage.
If C-Therm’s patented technology on the MTPS and the single-sided TPS sensors are of interest to you or any other sensor configurations (FLEX TPS, TLS, THW), feel free to contact us, or request a FREE quote below.
Email: info@ctherm.com
Request a Quote: https://ctherm.com/contact/request-quotation/
About the Author
Arya Hakimian is C-Therm’s resident Application Specialist. He has extensive experience in thermal analysis and materials characterization, and he holds a MSc in Chemistry and BSc in Medicinal and Pharmaceutical Chemistry from the University of New Brunswick.
References
[1] ISO 22007-7 – https://www.iso.org/standard/81222.html