The excellent properties of carbon fiber materials are widely used in aerospace, medical, sports equipment, building construction, etc. So everyone has a certain understanding of carbon fiber. Carbon fiber can be divided into three types: polypropylene carbon fiber, viscose silk and pitch fiber according to the different production materials. Because of the different production raw materials, the manufacturing methods are also different. For the manufacturing method of pitch-based carbon fibers, there are general-purpose (low-performance) isotropic methods; mesophase pitch to prepare carbon fibers; pre-mesophase method to prepare carbon fibers; potential Preparation of carbon fiber from mesophase pitch This lecture will introduce each method in detail, as follows:
1. Universal Isotropic Method
The general-purpose isotropic method uses petroleum pitch and coal tar pitch as raw materials, and removes low-boiling fractions and impurities and adjusts the carbon content in them by dry distillation, hydrogenation, or resinization, and then melt-spins them. The resulting filaments are oxidized and carbonized to obtain carbon fibers.
2. Mesophase pitch method
Add quinoline or pyridine (1-3 times) to asphalt, heat (80°C-120°C) and filter to obtain refined asphalt, place it in an inert gas, and treat it at (350-450)°C (2- 60) h, make it into mesophase pitch, and then melt-spin with pitch with 50%-70% mesophase content (high content, difficult spinning), the fiber formation speed is 127m/min, and the diameter is (10-15 ) μm, then non-melting treatment at (250-390) °C, and carbonization treatment at (1000-2000) °C to obtain high-performance carbon fibers.
3. Pre-mesophase method
The refined pitch was heated to 530°C in a salt bath and treated for 5 minutes to obtain pre-mesophase pitch with a content of about 35%, then spun, treated at 260°C for 15 minutes, and carbonized at 1000°C to obtain carbon fibers with a diameter of 10 μm.
4. Latent mesophase pitch method
The asphalt is thermally condensed at (350-500)°C to form polycyclic aromatic hydrocarbons. When its molecules reach a considerable size, they will be regularly arranged along a certain orientation to form small mesophase spheres with a laminated structure, that is, liquid crystals appear, also known as mesophase . Mesophase liquid crystal balls are spun, carbonized, and strengthened to obtain high-performance carbon fibers.
