You might be familiar with the carbon fiber by now. As many of its products are available in the stores, now ranging from the bicycles to watch the carbon fiber has undergone many improvement and development. However, still, most of you do not know how this unique material is manufactured.
So let us understand some of the different procedures through which the carbon passes to provide us with this lightweight and durable product.
The manufacturing process
The procedure for manufacturing carbon fiber is part mechanical and part chemical. The raw material is drawn into long strands or filaments and after that heated to a high temperature and it is made sure that the material is not exposed to oxygen.
Without oxygen, the fiber cannot catch fire. Rather, the high temperature causes the atoms in the fiber to vibrate until the vast majority of the non-carbon particles are removed. This procedure is called carbonization. This leaves the long fibers of carbon that are interlocked and only a few non-carbon atoms are left behind.
Here are the few procedures through which it undergoes:
Acrylonitrile plastic powder is blended with another plastic, similar to methyl acrylate or methyl methacrylate. The material is then reacted in the presence of a catalyst, in a solution polymerization or conventional suspension to produce polyacrylonitrile plastic.
The plastic is then spun into fibers utilizing one of a few unique techniques. In a few strategies, the plastic is mixed with specific chemicals and pumped through small jets into a quench chamber or the chemical bath where the plastic will coagulate and then set into a solid form.
This is the procedure used to manufacture polyacrylic material fibers. In different techniques, the heated plastic mixture is pumped through jets into a chamber where the solvents will evaporate, leaving a strong fiber. This part is very essential since the internal atomic structure of the fibers is formed during the spinning process.
The carbon fibers are then washed and to get the desired diameter they are stretched. The stretching technique will adjust the atoms inside the fiber and give the structure of the tightly bonded carbon crystal that is the result of carbonization process.
The manufacturers have to make sure that before the strands are carbonized, they should be synthetically changed in order to convert the linear atomic configuration to an even more thermally stable configuration called the ladder bonding. This is made possible by heating the fibers in air to a high temperature of around 390-590° F (200-300° C) for 30 to 120 minutes.
This causes the fibers of carbon to get oxygen particles from the air and change their nuclear bonding configuration. The procedure of stabilization consists of many chemical reactions and many of them take place at the same time.
The heat that is naturally generated from the fibers is then controlled to avoid overheating that might disturb the reaction. Economically, for the procedure of stabilization, many techniques and equipment are required and thus it is not an easy task.
In a few procedures, the fibers have to be passed through many heated chambers to get the best result. In others procedures the fiber is:
- Passed through heated rollers
- Passed on heated beds
- Suspended in a chamber and hot air is blown over them
- Passed through heated air mixed with catalyst
The fibers are heated up to a temperature of around 1,830-5,500° F (1,000-3,000° C) for a few minutes, once they are stabilized in a chamber that is loaded with a mixture of gasses that does not contain oxygen. In such a high temperature, the absence of oxygen prevents the fibers from burning out.
The pressure of gas inside the chamber is kept more than that of the outside. The openings through which the fibers enter or exit the chamber are sealed so that oxygen cannot enter it.
As the fibers are heated, they will start losing the non-carbon atoms with some of the carbon atoms because of the vibrations and thus it will include:
- Water vapor
- Carbon monoxide
- Carbon dioxide
As the non-carbon particles are removed, the rest of the carbon particles are framed firmly into carbon crystals that are adjusted pretty much parallel to the long chain of the fiber. In a few procedures, two heating chambers working at two optimum temperatures are utilized to better control the rate of heating when the process of carbonization is taking place.
Treating the surface
After the process of carbonizing, the fibers have a surface that does not bond well with the resins and different materials utilized as a part of composite materials. To give the carbon fibers better bonding qualities, their surface is slightly oxidized.
Oxidation can be accomplished by adding various gasses or liquids for example
- Carbon dioxide
- Sodium hypochlorite
- Nitric acid
The fibers are electrically coated as well. The fiber is made the positive electrode in the bath that is filled with the chemical that has to be coated. The process is done under strict supervision because if any issue occurs it might cause the formation of pits that will lead to the carbon fiber failure.
After the surface treatment, the carbon fibers are covered for protection against damage that might occur during the process of winding or weaving. This procedure is known as sizing.
The materials that are selected to be coated are wisely chosen so that they can meet the properties of the carbon fiber. Mostly utilized coating materials are
After the coating is done the fibers are then wound around the cylinders that are called bobbins. These bobbins are then loaded into the spinning machines that will twist the fibers into yarns of different sizes.
So the carbon fiber is manufactured. It will be now transported to several industries for the production of different kinds of products that will be useful for the mankind.