Testing.7 – Thermal Conductivity Testing on High Temperature Polymers – Fluorinated Ethylene Propylene (FEP)

Sep 17, 2015 | Blog, Testing |

A sample of fluorinated ethylene propylene (FEP) was tested for thermal conductivity and thermal diffusivity using the Hot Disk Transient Plane Source (TPS) 2200 instrument. This instrument has the capability of measuring absolute bulk and directional thermal conductivity and thermal diffusivity for solids, liquids, pastes and powders without the need for calibration or contacts agents. Thermal conductivity ranges from 0.03 W/m•K to 500 W/m•K are measureable with this system.

Thermal property measurements were performed using the convenient Hot Disk TPS single-sided sensor. The TPS single-sided sensor is ideal when only one sample piece is available or when the experimenter is testing large hard to handle samples.

Belonging to the same family of resins as polytetrafluoroethylene (PTFE) and perfluoroalkoxy (PFA), fluorinated ethylene propylene is most commonly used for computer wiring, extrusion, chemical processing equipment, and coatings. The product resin of a copolymerization between tetrafluoroethylene and hexafluoropropylene, it is the most chemically inert of all plastics. It has an exceptionally high degree of stress crack resistance, ability to withstanding very low and high temperature extremes and excellent dielectric properties.

Transient Plane Source Bulk Measurements:

Experimental set up is extremely easy, and achieved by placing the material sample on top of the sensor. A weight is added on top of the sample to ensure good sensor to sample contact. This unique sensor offers excellent accuracy and repeatability without the requirement of two pieces of sample. The TPS single-sided sensor may also be inverted for larger samples.

Thermal Conductivity Blog FEP

Figure 1. Fluorinated ethylene propylene (FEP) experimental set up

 

Parameters of test time for FEP: 80 seconds @ 0.1 W were selected to ensure representative 3-dimensional heat penetration, without testing beyond any of the dimension boundaries of the sample.  This is easily determined as the Hot Disk TPS measures the thermal diffusivity (mm2/s), thus the penetration depth is calculated and displayed. It is important to make sure the penetration depth from measurement is less the available probing depth, as this will result in a clean signal free of any reflections.

Once measurement is complete, the contact resistance between sensor and sample may be removed by simply selecting and removing the portion of time which represents the non-linear portion of the temperature vs time curve.  This is easily accomplished with the easy to use Hot Disk TPS 7.2.1 Software.

After calculations, the testing results of thermal conductivity (W/m•K) and thermal diffusivity (mm2/s) for the sample materials are displayed (See Table 1).

Table 1. Thermal conductivity and thermal diffusivity for fluorinated ethylene propylene (FEP)

Bulk Thermal Conductivity
(W/m•K)
Bulk Thermal Diffusivity
(mm2/s)
Standard
Deviation
(for λ*)
0.21953 0.13689 0.0006939

 

When compared to our reference values (0.20 ± 0.04 W/m•K), the experimental results fall within the specified conductivity range.

Sources

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* where λ is thermal conductivity