In the traditional sense, metals would typically be utilised for thermal management applications due to their inherently high thermal conductivity. Standard plastics, on the other hand, possess very low levels of thermal conductivity and indeed would be thought of as thermal insulators, with applications to suit.
Plastics in the form of injection moulded components or custom extruded profiles do offer many advantages over, for example, metals. These include:
• Low weight
• Chemical and corrosion resistance
• Electrical insulation
• Rapid manufacturing process
• Complex geometries
• Application specific property modification
• Pigmenting potential
• Possibility to combine parts in a single operation
• Potential cost reductions
• Elimination of processing steps
In order to take advantage of such benefits in thermal management situations, the thermal conductivity level of standard base plastics needs to be increased. Such an increase can be achieved by incorporating high thermal conductivity additives into the base plastics via compounding techniques. Such additives can be incorporated into a wide range of plastics, ranging from commodity up to high performance.
Typically used in heat sinks for electronic devices and LED lights, geothermal pipes, thermally conductive pads and battery cooling systems, KONDUCT thermally conductive polymers can be offered as electrically insulating or conductive and developed to meet your specific thermal management challenges.
Heat transfer occurs via three main mechanisms:
Energy transfer away from an emitting source via electromagnetic waves. Can occur through a vacuum or solid/fluid.
Energy transfer between a solid surface and a surrounding fluid (liquid/air). Such transfer is related to the conditions of the whole system in consideration and not to a specific material property.
Transfers heat via molecular collisions and requires physical contact. The process itself depends upon the existing temperature gradient, cross-section/dimensions of the component and the physical properties of the material in question (thermal conductivity).
When designing for thermal management and the control thereof, all of these mechanisms need to be considered as a whole, along with their effect on the entire system.
Commonly used metals have far higher base thermal conductivity values than thermally conductive plastics. However, this is not the whole story and, as previously stated, when it comes to thermal management the whole system needs to be considered. For many applications which do not involve forced air cooling (natural convection only), the increased thermal conductivity of a metal can lead to a bottleneck at the component surface, with the convection cooling unable to keep up. In these situations, the high base thermal conductivity is effectively wasted in the overall thermal management picture. Under the right conditions and with a good design, thermally conductive plastic components have been shown to more closely match natural convection cooling and hence be capable of matching the overall thermal management capabilities of an equivalent metal component. With design optimisation, performance can even exceed that of an existing metal component.
Thermally conductive plastics are almost entirely dependent upon the additive system utilised in terms of the thermal conductivity achieved in the final material. Hence, there are many considerations to take into account when designing and utilising such materials in the optimum manner.
The video below illustrates the heat flow across a thermally conductive plastic (bottom sample) compared with a standard plastic (top).
There are several methods for measuring thermal conductivity of materials, with each having their own advantages. Radical Materials utilises the laser flash method (ASTM E-1461, DIN EN 821 and DIN 30905), to accurately report thermal conductivity of planar samples in both the through-plane and in-plane orientations.