1 What is mesophase pitch-based carbon fiber?
Carbon fiber is a graphite microcrystalline material formed by stacking graphite flake crystallites along the fiber axis direction. More than 90% carbon content and mainly classified into PAN carbon fiber, pitch-based carbon fiber (MPCF) and viscose-based carbon fiber according to different raw material sources. Pitch-based carbon fiber is further classified into isotropic (general level) pitch-based carbon fiber and anisotropic, which also called mesophase pitch-based carbon fiber, depending on the different materials and processes. Mesophase pitch-based carbon fiber has excellent properties such as high specific modulus, high specific strength, high thermal conductivity, corrosion resistance, creep resistance, low thermal expansion coefficient, high-temperature resistance, and electromagnetic shielding. The most outstanding performance is high modulus and high thermal conductivity. Its modulus can reach 800GPa or more, and the thermal conductivity can reach 800w/m·K or more, even more than 1000w/m·K.
2 The structure characteristics of mesophase pitch-based carbon fiber
MPCF is processed from heavy aromatic hydrocarbons. Due to the characteristics of raw materials and processes, its microstructure is also unique. The raw material forms a large-sized planar aromatic molecule structure by polycondensation, further development a parallel stacked mesophase sphere, and then the sheet macromolecules are aligned along the fiber axis by spinning and drawing. This highly oriented lamellar structure is more conducive to the formation of graphite microcrystals in the subsequent treatment, and then it is easier to obtain high modulus and high thermal conductivity.
3 Why use mesophase pitch-based carbon fiber?
MPCF has high modulus and high thermal conductivity that other materials can’t match.
The mechanical properties of the material are generally expressed in its tensile strength, tensile modulus, dimensional stability, etc. For general industrial applications, the basic reinforcement fiber can meet the requirements. However, in the fields of aerospace, satellites, industrial robots, precision industrial rollers, pressure vessels, and automotive lightweight, high-modulus materials are very important. For example, large aircraft wings made from conventional materials are prone to sloshing during the take-off and landing process, while mesophase pitch-based carbon fiber modulus is extremely high, and the composite made of it has good rigidity, maintaining good stability during flight. The satellite antennas in order to ensure measurement accuracy, can’t be deformed in the process of monitoring, which requires high modulus materials. In the ALMA probing deep space project jointly carried out by the United States, Europe, and Japan, 80 electromagnetic wave telescopes with a diameter of 12 meters were installed in the deep mountains of South American intelligence. The main structural materials of the antennas were made of mesophase pitch-based carbon fiber composite materials. In addition, pressure vessels, industrial roller shafts, and construction reinforcement all need high modulus materials.
Experiments have placed pitch-based carbon fiber composites under 1000 ° C flame, which has not burned for more than 10 minutes, while other fiber composites burned within a few tens of seconds. Because pitch-based carbon fiber has a high thermal conductivity, it can quickly dissipate heat to keep the surface of the material at a lower temperature. This is important for aerospace vehicles operating in extremely high-temperature environments. It is also a key material to solve the heat dissipation problem of electronic products, aircraft and rail vehicle brake systems.