Written by Sarah Ackermann, Laboratory Services Manager (BSc, MSc), and AJ (Ajinkya) Dhale, Business Development Manager (MBA, ChemE)
The Steady State Method is a popular approach to test the insulation properties of textile materials. As technology evolves, different methods emerge, such as the Modified Transient Plane Source, which has been growing as another choice for textile researchers to measure thermal conductivity.
In the tests presented below, we are comparing the thermal conductivity values of a non-woven fabric, Polyester Felt, obtained by a Heat Flow Meter (HFM) conforming to ASTM C518, with measurements taken using the Modified Transient Plane Source Method (MTPS) conforming to ASTM D7984.
ABOUT POLYESTER FELT
Polyester Felt is a non-woven material made from polyester fibers or recycled plastic bottles. This textile has high stability against degradation when subjected to heat, and it is also resistant to organic, oxidizing, and ambient conditions.
This material is also used in gaskets, filtration applications, and as padding material in a broad range of industries. Other popular applications include window lining, steel wiping, floor protection, weatherstripping, to name a few.
TEST SET-UP DETAILS
During our tests, we have maintained the same ambient temperature and atmospheric conditions for both equipment. A Compression Test Accessory has been employed and deemed a complementing instrument to MTPS capabilities in measuring the thickness of the material.
Figure 1. Setup on MTPS (ASTM D7984) with Compression Test Accessory
Figure 2. Setup on Heat Flow Meter (ASTM C518)
TEST SUMMARY AND RESULTS
Sample 1 was tested using the Textiles 1 calibration and presented valid testing thickness. The reported thermal conductivity (k) and associated relative standard deviation (RSD) are the averages of 15 measurements. The temperature was not controlled during testing (Room Temperature 22.8°C[1]). The thickness was controlled to 6.38 mm to ensure similar compression. The test results are summarized in Table 1.
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Sample ID |
Results[1] |
Time |
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Avg k (W/mK) |
RSD (%) |
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MTPS |
0.0357 |
0.6 |
10 – 15 mins |
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HFM |
0.0351 |
0.5 |
6 hours |
Table 1. Test Results MTPS vs HFM
The thermal conductivity values acquired are very similar between methods, with a difference of about 1.7%. This is within the typical reproducibility range of the methods. The biggest advantage of using MTPS over HFM is the test time. HFM takes about 24 times longer to provide the results than MTPS. In addition, the HFM requires a larger sample size to fit between the two plates, which can be inconvenient when sample material is limited.
Additionally, the thermal resistance (R) of the textile fabric can only be calculated if the thickness of the material is known. This article highlights the formula necessary to compute the R value of the material and convert it into different units of thermal resistance – clo and togs.
For information on the setup highlighted in this blog post, or for information on how to get contract testing using this test setup, contact us here or at +1-506-457-0498.
About the Authors
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Sarah Ackermann is our laboratory services manager. She has extensive experience in thermal analysis and materials characterization and has been helping clients with their thermal testing problems for over five years. She holds a MSc in Chemistry and BSc in Medicinal Chemistry from the University of New Brunswick. |
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AJ (Ajinkya) Dhale is a Business Development Manager at C-Therm and helps researchers in the Middle East and South Asia to achieve their thermal conductivity objectives. AJ has experience working in diverse chemical industries in the capacity of manufacturing specialist, technical consultancy, and business development.
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