Testing.6 – Thermal Conductivity Testing on General Plastics Polymers– Polyvinyl Chloride (PVC)
Thermal property measurements were conducted on polyvinyl chloride (PVC) samples. Material samples were 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.
In comparison, CPVC or chlorinated polyvinyl chloride is considered to be the cousin to PVC. Both polymer thermoplastics are used primarily in welding, machining, and forming, more specifically in hot and cold water piping and industrial liquid handling. They are also inert to many chemicals including: alcohols, strong acids, alkalis, and salt solutions. Conversion from PVC into CPVC comes from a chlorine gas reaction to the PVC resin. In some cases CPVC would be the preferred choice due to the higher corrosion resistance at high temperatures (up to 200°F).
Alongside testing of polyvinyl chloride, other polymers to be tested include: high density polyethylene (HDPE), low density polyethylene (LDPE), polyoxymethylene, acrylonitrile butadiene styrene (ABS), polyphenylene oxide, and polyproplene.
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.
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 PVC: 40 seconds @ 0.1W 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 3).
Table 3. Thermal conductivity and thermal diffusivity for Polyvinyl Chloride (PVC).
|Bulk Thermal Conductivity
|Bulk Thermal Diffusivity
When comparing the experimental results to reference values obtained by ASTM C177, polyvinyl chloride was found to be extremely close with better than 5% accuracy.
* where λ is thermal conductivity