With the rise of LED industry, thermal conductive plastics have attracted more and more attention. What is thermal conductive plastics? What is the principle of heat conduction? What are the classifications of thermal conductive plastics? Besides led, where else can thermal conductive plastics be applied?

1、 What is thermal conductive plastics

Thermal conductive plastics is the use of thermal conductive fillers (including particles, fibers, laminates, etc.) to uniformly fill the polymer matrix material, in order to improve its thermal conductivity. The thermal conductivity is mainly measured by the thermal conductivity (unit: w / (m.k)).

2、 Common matrix materials and fillers

The main components of thermal conductive plastics include matrix materials and fillers. The matrix materials include PPS, PA6, PA66, PA12, PA46, LCP, TPE, PC, PP, PPA, peek, etc. The thermal conductivity of the heat conducting body material is as follows:

Fillers include the following metal and inorganic fillers:

1. Metal powder filler: copper powder, aluminum powder, iron powder, tin powder, nickel powder, etc.

2. Metal oxides: alumina, bismuth oxide, beryllium oxide, magnesium oxide, zinc oxide.

3. Metal nitrides: aluminum nitride, boron nitride, silicon nitride.

4. Inorganic nonmetal: graphite, silicon carbide, carbon fiber, carbon nanotubes, graphene, beryllium carbide, etc.

The thermal conductivity of common thermal conductive fillers is as follows:

3、 Classification of thermal conductive plastics

Thermal conductive plastics can be divided into thermal conductive plastics and thermal conductive insulating plastics. The electrical insulation properties of most thermal conductive plastics are ultimately determined by the insulation properties of filler particles.

1. Insulating and heat conducting plastics

The main components of insulating and thermal conductive plastics include: Plastics + fillers + others, among which fillers include: metal oxides Al2O3, MgO, SiO2, metal nitrides AlN, Si3N4, BN, SiC, b4c3, etc.

Because the filler particles are non-conductive particles, plastic insulation is caused. The thermal conductivity of this kind of thermal conductive plastics is not high, generally about 1.5w/m.k.

2. Conductive plastics

The main components of conductive and thermal conductive plastics include: Plastics + fillers + others, among which fillers include: metal powder, fiber, graphite, carbon fiber, CNT, graphene, etc. because this kind of fillers belong to conductive particles, the corresponding thermal conductive plastics are also conductive. The thermal conductivity of this kind of thermal conductive plastics is relatively high, which can generally reach more than 5.0w / (m.k).

4、 Heat conduction mechanism of heat conductive plastics

The thermal conductivity of thermal conductive plastics depends on the interaction between polymer and thermal conductive fillers. Different kinds of fillers have different thermal conductivity mechanisms.

1. Metal filler: the heat conduction of filler mainly depends on the movement of electrons, which is accompanied by heat transfer.

2. Nonmetallic fillers: the heat conduction of nonmetallic fillers mainly depends on the phonon heat conduction, and the heat diffusion rate mainly depends on the vibration of adjacent atoms or binding groups, including metal oxides, metal nitrides and carbides.

5、 Factors affecting thermal conductivity of thermal conductive plastics

1. Types and characteristics of polymer matrix materials: the thermal conductivity of matrix materials is super high, the better the dispersion of fillers in the matrix and the better the combination of matrix and fillers, the better the thermal conductivity of thermal conductive composites.

2. Types of fillers: the higher the thermal conductivity of fillers, the better the thermal conductivity of thermal conductive composites.

3. Shape of fillers: Generally speaking, the order of easily forming thermal conduction path is whisker > fibrous > flake > granular. The easier the fillers form thermal conduction path, the better the thermal conductivity.

4. Content of fillers: the distribution of fillers in polymer determines the thermal conductivity of composites. When the filler content is small, the heat conduction effect is not obvious; When the filler is too much, the mechanical properties of the composites will be greatly affected. When the filler content increases to a certain value, the interaction between fillers forms a network or chain like heat conduction network chain in the system. When the direction of the heat conduction network chain is consistent with the direction of heat flow, the heat conduction performance is the best. Therefore, there is a critical value for the amount of thermal conductive filler.

5. The bonding characteristics of the interface between filler and matrix material: the higher the bonding degree between filler and matrix, the better the thermal conductivity. The thermal conductivity can be increased by 10% - 20% by selecting appropriate coupling agent for surface treatment of filler.

6、 Application of thermal conductive plastics

At present, thermal conductive plastics are widely used in LED field. In addition, thermal conductive plastics are also used in pipes, heat exchangers, automobiles, heating / cooling / refrigeration, etc.

7、 Types and application of thermal conductive plastics