Apparent thermal conductivity of multiple layers of coatings

Related services Thermal conductivity

We have a post on the measurement of thin paint and coating thermal conductivity with the ASTM D5930 method. Many surfaces are coated with multiple layers of coatings. How to determine the apparent thermal conductivity of such multilayer coating systems?

The method described in the post is only applicable to one single layer of coating. For a surface coated with two or more layers of coatings, the method can only measure the top layer, but cannot determine the apparent thermal conductivity of multiple layers.

To determine the apparent thermal conductivity, the calculation method needs to be used. In this post, we use a two-layer coating system as an example:

  1. Measure the thermal conductivity of each layer individually (k1 and k2). Note: the samples need to be prepared individually too, as the method can measure the top layer only.
  2. Calculate the overall thermal resistance: R = d1/k1 + d2/k2, where d1 and d2 are the thickness of each layer.
  3. Calculate the apparent thermal conductivity: k = (d1 + d2)/R

For the calculation of the overall thermal resistance, our online ETTV U-value calculator can be used. The R-value result reported is the overall thermal resistance of all layers in the system.

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