What Is a Thermally Conductive Material? Definition & Types
1. Definition and the Metric That Matters
A thermally conductive material is a plastic composite made by adding thermally conductive metal oxides, graphite fibers or carbon fibers to ordinary plastics in order to improve their thermal conductivity.
Thermal performance is mainly measured by thermal conductivity (unit: W/(m·K)). The higher the thermal conductivity, the better the material conducts heat.
2. The Two Categories of Thermally Conductive Plastics
Thermally conductive plastics fall into two broad categories:
- Electrically conductive thermally conductive plastics
- Electrically insulating thermally conductive plastics
Which one you need depends on the electrical environment of the product: applications that must remain insulating (LED luminaire housings, electronic packaging parts) require electrically insulating thermally conductive plastics.
3. Main Composition: Base Material and Fillers
Thermally conductive plastics consist mainly of a base material and fillers.
Base materials
PPS, PA6/PA66, LCP, TPE, PC, PP, PPA, PEEK, and others.
Fillers
AlN (aluminum nitride), SiC (silicon carbide), Al2O3 (aluminum oxide), graphite, fibrous high-thermal-conductivity carbon powder, flake-shaped high-thermal-conductivity carbon powder, and others.
4. The Three Filler Types and How to Choose
There are three main types of thermally conductive filler: carbon materials, inorganic thermally conductive particles, and metal particles.
Selection logic: given the cost and insulation requirements of these plastics, inorganic thermally conductive particles are almost always chosen. Among them, aluminum oxide, magnesium oxide and zinc oxide are the most widely used because they are relatively inexpensive and make it easy to adjust the cost and whiteness of the finished plastic. Other high-thermal-conductivity fillers are of course used to meet higher thermal requirements, at a cost that steps up accordingly.
5. Al2O3 vs. MgO vs. ZnO: Common Inorganic Particles Compared
| Filler | Thermal conductivity | Loading behaviour | Overall assessment |
|---|---|---|---|
| Magnesium oxide (MgO) | Relatively high | Thickens easily — whether the loading can be raised is a problem | Good conductivity, limited loading |
| Aluminum oxide (Al2O3, flake) | Moderate | After modification, high loadings are easy to reach | The most balanced option; high loading after modification |
| Zinc oxide (ZnO) | The lowest | Relatively hard to fill in large amounts | Limited in both conductivity and loading |
Conclusion: for balanced high loading, cost and insulation, modified flake aluminum oxide is the first choice; where conductivity comes first and a loading limit is acceptable, magnesium oxide is an option; zinc oxide, limited in both conductivity and loading, is mostly used where thermal requirements are not demanding.
6. FAQ
Q1: What is a thermally conductive material? A: A plastic composite made by adding thermally conductive metal oxides, graphite fibers or carbon fibers to ordinary plastics to improve their thermal conductivity.
Q2: How is thermal performance measured? A: Mainly by thermal conductivity, in W/(m·K).
Q3: What are the two categories of thermally conductive plastics? A: Electrically conductive and electrically insulating thermally conductive plastics.
Q4: What are the main components? A: A base material and fillers. Base materials include PPS, PA6/PA66, LCP, TPE, PC, PP, PPA and PEEK; fillers include AlN, SiC, Al2O3, graphite, fibrous high-thermal-conductivity carbon powder and flake-shaped high-thermal-conductivity carbon powder.
Q5: What are the three main filler types? A: Carbon materials, inorganic thermally conductive particles and metal particles. Given cost and insulation requirements, inorganic thermally conductive particles are generally chosen.
Q6: How do Al2O3, MgO and ZnO differ? A: Magnesium oxide has relatively high thermal conductivity but thickens easily, limiting loading; flake aluminum oxide offers moderate conductivity and, after modification, high loadings; zinc oxide has the lowest conductivity and is hard to fill in large amounts.
Shenzhen RenJie Plastic Materials Co., Ltd. is a well-known specialized manufacturer of thermally conductive plastics in China and holds a leading domestic position in the development and production of thermally conductive materials. Sales hotline: 18681139818; Contact: Tang Jihua.