Expanded Polystyrene Board (EPS Foam) is a widely used plastic for applications in packaging and building insulation. It has a very low thermal conductivity property, and therefore is an ideal material for providing thermal insulation.
The Chart I below shows the TCi’s results on a certified reference sample material of EPS provided by the National Institute of Standards and Technology (NIST) measured via the guarded hot plate (GHP) technique. GHP is a highly accurate and reliable method for measuring thermal conductivity – but it takes hours to run a sample and the wait-time for results – coupled with the onerous sample size requirements – can add up to a significant burden for some users.
As graphically presented in Chart I, the average test results generated with the C-Therm TCi Thermal Conductivity Analyzer on the NIST reference sample is 0.0329 W/mK with an RSD of 0.19%. This represents a difference of 2.13% from the stated NIST value measured with GHP of 0.0337 W/mK. All testing was done at approximately 24°C.
In testing within 2.13% of the stated reference value, the test results fall within the 2.4% uncertainty noted on the NIST certificate for the reference standard material. These test results exemplify the high accuracy clients typically achieve in characterizing a wide range of sample materials with the C-Therm TCi Thermal Conductivity Analyzer.
The following testing results highlight application of the TCi in quality control testing for insulation materials. A sample of EPS was sourced from the local Home Depot store in Fredericton, New Brunswick. The TrueFoam™ sample was tested in 10 different locations in assessing both the overall quality of the insulation material, and also the sample homogeneity. In Chart II these results are plotted – note that this time the X-axis plots different locations of measurement in contrast to Chart I above that plots multiple measurements on the same location. Test results demonstrate the product provides excellent insulation quality with an average thermal conductivity of 0.033 W/mK and is highly homogeneous in its performance across multiple locations with a relative standard deviation 0f 0.6%. As the product has a specification of better than 0.0363 W/mK, C-Therm found the insulation to surpass the stated performance specification for the product. All testing was completed within 10 minutes (each measurement took less than 3 seconds with a 60-second interval period between measurements).
In manufacturing, the C-Therm TCi Thermal Conductivity Analyzer offers added insight in being able to accurately and quickly measure the thermal conductivity of products so production can understand if they are meeting specifications consistently. In this example, the test results tested better than the stated thermal conductivity and the sample material is of excellent consistency.