Testing.4 – Thermal Conductivity Testing on High Temperature Polymers –Ultem (PEI)
Following the testing of Torlon (polyamide-imide), measurements were taken on a close relative, polyetherimide with the brand name Ultem. This is the second sample of high-temperature polymers, in our high temperature polymer series, which was tested for thermal conductivity and thermal diffusivity using the Hot Disk Transient Plane Source (TPS) 2500 S 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 0.01 W/m•K to 1800 W/m•K are measurable.
In addition to Torlon and Ultem, other possible polymers to be tested are: fluorinated ethylene propylene, poly(etherether-ketone), polysulfone, polyphenylene sulfide, poly(phenylene-sulfone), and polytetrafluoroethylene.
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 testing large hard to handle samples.
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.
Parameters of test time for Ultem: 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, 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 Ultem sample are displayed (See Table 2).
Table 2. Bulk thermal conductivity and thermal diffusivity for Ultem PEI.
Bulk Thermal Conductivity
When compared to the reference value obtained by ASTM C177 (0.220 W/m•K), the measured bulk value was found to be very similar to that of the reference with a 1.7% difference.