What is Thermal Conductivity?
Thermal conductivity is at the core of TALs services offerings. We are global leaders in thermal conductivity measurements and specialize in niche testing applications across a wide range of sample types.
Thermal conductivity is a measure of a materials ability to transfer heat most often denoted as (λ, k or K-value). Thermal conductivity differs with each substance and may depend on structure, density, humidity, pressure and temperature. Materials having a large thermal conductivity value are good conductors of heat; whereas ones with a small thermal conductivity value are poor conductors of heat (i.e. good insulators). Thermal conductivity is typically represented in units of (W/mK).
Why is Thermal Conductivity Important?
Thermal conductivity can generally fall into one of two main categories of importance. One being applications where temperature needs to be dissipated quickly and the other where temperature needs to be maintained. The former would be applicable to devices which are used to remove heat from sensitive componentry where a buildup of heat could otherwise cause serious damage. In this case, high thermal conductivity materials are of significant value. The latter would represent cases where minimizing heat loss plays a significant role such as cases where drastic changes in temperature can prove detrimental. Here, low conductivity materials add value.
How much does Thermal Conductivity Testing Cost?
Thermal conductivity testing rates will vary based on the testing method and conditions – generally transient testing methods are the most cost-effective as they have shorter test time and generally less strict sample size requirements. Click on the Request Quote button or contact us for more information and a free, no obligation quotation.
Recommended Methods
TALs portfolio of thermal conductivity testing offerings include multiple transient-based, steady-state and flash techniques. The best-suited method is often dictated by sample type, sample size and temperature range of interest. To find out the best method for your testing needs contact us at info@thermalanalysislabs.com or call (506) 457-0498.
We offer a wide range of methods for determining thermal conductivity and below is a selection of the measurement requirements for thermal conductivity testing services.
Modified Transient Plane Source (MTPS)
The MTPS method employs a single-sided, interfacial heat reflectance sensor that applies a momentary constant heat source to the sample. Typically, the measurement pulse is between 1 to 3 seconds. The temperature behavior as a function of time is analyzed with the aid of a calibration to give thermal properties of the sample. Thermal conductivity and effusivity are measured directly, providing a detailed overview of the heat transfer properties of the sample material.
| Measurement Range | 0 to 500 W/mK |
| Sample size | Min. diameter of 18 mm Min. thickness is dependent on thermal conductivity |
| Temperature range | -50 to 200 °C |
| Recommended Material types | Solids, liquids, powders and pastes |
| ASTM/ISO/EN Standards | ASTM D7984 |
Transient Plane Source (TPS)
The TPS method employs a double-sided hot disc sensor to apply a heat pulse of several seconds to a few minutes to the sample. Temperature of the sensor is monitored with time and data is regressed to simultaneously determine thermal conductivity, thermal diffusivity and specific heat capacity of materials from a single measurement.
| Measurement Range | 0.03 to 2000 W/mK |
| Sample size | Dependent on sensor size* |
| Temperature range | -50 to 300 °C |
| Material types | Solids and powders |
| ASTM/ISO/EN Standards | ISO 22007-2 |
Transient Line source (TLS)
The TLS method employs an electrically heated needle-shaped sensor which is embedded into a material. The heat flows out radially from the needle into the sample. During heating, the temperature difference between a thermocouple (T1) positioned in the middle of the heating wire, and a second thermocouple (T2) located at the tip of the needle is measured. By plotting this temperature difference versus the logarithm of time, thermal conductivity can be calculated. Typically, the measurement is on the order of 2-10 minutes.
| Measurement Range | 0.1 to 6 W/mK |
| Sample size | Min. volume of 77 mL |
| Temperature range | -55 to 180 °C |
| Material types | Melts, soils and viscous fluids |
| ASTM/ISO/EN Standards | ASTM D5334, D5930 and IEEE 442-1981 |
Heat Flow Meter (HFM)
The HFM method involves placing an insulative sample between a hot and cold plate held at a constant temperature difference. The heat flux is monitored until the system reaches steady-state. When steady-state is reached, heat flux, temperature difference and sample thickness are used, along with a calibration, to determine thermal resistivity, thermal conductivity, thermal resistance and thermal conductance of the sample.
| Measurement Range | 0.002 – 1.0 W/mK |
| Sample size | 100 x 100 mm or 300 x 300 mm Min. thickness of 5 mm |
| Temperature range | -10 to 60 °C |
| Material types | Foams, aerogels, polymers and vacuum insulation panels |
| ASTM/ISO/EN Standards | ISO 8301, ASTM C518, EN 1946-3, EN 12664, EN 12667 and EN 12939 |
Xenon Flash Apparatus (XFA)
The XFA method involves flashing a brief pulse of infrared (IR) radiation at a specially-coated sample of known thickness and cross section. An IR camera on the far side of the sample monitors the change in sample temperature with time. This temperature-time behavior is regressed to determine the thermal diffusivity of the sample. With a comparison to a known thermally similar material, or with input of known sample thermal properties, thermal conductivity may be determined.
| Measurement Range | 0.1 to 2000 W/mK |
| Sample size | 12.5 x 12.5 mm Min. thickness of 1 mm |
| Temperature range | 25 to 500 °C |
| Material types | Solids |
| ASTM/ISO/EN Standards | ASTM E1461 |
Other methods may be available. Contact us at info@thermalanalysislabs.com or call (506) 457-0498 to discuss.