Japan’s New Energy and Industrial Technology Development Organization (NEDO) has unveiled a new manufacturing process for carbon fibers that reduces power consumption and C02 emissions.
Compared with a conventional manufacturing process for polyacrylonitrile (PAN)-based carbon fibers, the new process is said to achieve 10 times higher productivity.
The conventional manufacturing process consists of four processes. First, PAN dissolved in a solvent is formed into threadlike PAN fibers (filature). Second, the PAN fibers are oxidized by thermal treatment to improve their heat resistance before they are carbonized – basically a flame-retardant treatment.
Once the flame-retardant PAN fibers once carbonized at a high temperature (carbonization), they are then subjected to surface treatment. Among the four processes, the main bottleneck so far as been the flame-retardant treatment. Flame-retardant treatment is hard to be controlled, making it difficult to process a large number of PAN fibers.
NEDO’s new process uses a solvent-soluble flame-retardant polymer to eliminate the need for the flame-retardant treatment. The polymer can be easily formed into threads. When the polymer is formed into threads, it already has flame retardancy. Therefore, flame-retardant treatment, which is usually conducted after filature, is not necessary.
The solvent-soluble flame-retardant polymer is made by adding a dissolution promoter and oxidant to clothing PAN, which is inexpensive.
In addition to the eliminating the flame-retardant treatment, the new technology directly heats materials for carbonization by using microwaves. As a result, it is no longer necessary to keep a high temperature in a carbonizing furnace – thus making it possible to reduce the time it takes to carbonate materials.
NEDO also developed a new technology for surface treatment by using plasma. It helps simplify the surface treatment process and can reduce the energy consumed in the process by about 50%, in comparison with conventional methods.
Image credits: NEDO