The Chemistry of Carbon Fiber

Introduction

    • Carbon Fiber is a widely used plastic around the world. It has many uses and has replaced many composite materials because of its incredible tensile strength. It is almost 3 times stronger than steel. It is also very light, unlike metals. I chose carbon fiber because it is being used more and more everyday. It is replacing metal parts and pieces making them lighter and in some cases, safer. Carbon Fiber will be a big part of my life because 3D printers are able to print things in different materials such as Carbon Fiber.Composition of ...Polyacrylonitrile- (C₃H₃N)ₙ
    • Carbon- C
    • Proprietary Gases and Liquids
    • Acrylonitrile(plastic powder)-CH₂CHCN
    • Methyl acrylate-CH₂CHCO₂CH₃₋
    • Methyl methacrylate-C₅H₈O₂
    • Water Vapor-H₂O
    • Ammonia-NH₃
    • Carbon monoxide-CO
    • Carbon dioxide-CO₂
    • Hydrogen-H₂
    • Nitrogen-H₂
    • Sodium Hypochlorite-NaCIO
    • Nitric Acid-HNO₃
    • Epoxy
    • Polyester-(C₁₀H₈O₄)
    • Nylon-(C₁₂H₂₂N₂O₂)
  • Urethane-C₃H₇NO₂

Main Chemicals, Compounds, Components

Polyacrylonitrile

One of main components of carbon fiber, is semicrystalline polymer resin, known as Polyacrylonitrile.

To form polyacrylonitrile, a plastic powder called acrylonitrile must be mixed with methyl acrylate or methacrylate and reacts to a catalyst in a polymerization process. This plastic is then spun into fibers. There are many methods, like mixing the plastic with certain chemicals and pumping them through tiny jets into a chemical bath. Can also be put into a quench chamber where the plastic coagulates and hardens into the solid fibers. The fibers are then stretched and aligned to the desired diameter. This allows the molecules to align and to provide a base for the formation for the tightly packed carbon crystals. It then has to be stabilized to become more thermally stable in terms of ladder bonding, so that the fibers will not burn in the Carbonization process. The stabilization process is very complex, and can be done in many different methods using many different machines. The whole goal, is to heat up the fibers so that they pick up oxygen molecules, that causes to rearrange their atomic bonding pattern. From there, it gets carbonized and oxidized and is then ready for sizing.

One of the other main components of carbon fiber, is carbon itself. Once the polyacrylonitrile goes through the carbonization process, it causes all the non-carbon atoms to be leave. Once they are gone, you are left with fiber with long strands of very tightly bonded carbon atoms. Because of the tightly packed chains of carbon atoms, it has an incredible amount of strength.

Chemistry's Role

Once the polyacrylonitrile is made and stabilized, it is ready for the Carbonization process. The fibers have to be heated to extreme temperatures going all the way high as 5,500℉ for several minutes. This has to be done in a furnace that does not contain any oxygen whatsoever, so that the fibers do not burn. As this is being done, the air pressure inside the furnace is higher than the air pressure outside to also insure that no oxygen can creep in. During this process, all the non carbon atoms fade away and you are left with fibers that have tightly bonded carbon crystals. After the fibers have been carbonized, they need to be oxidized. Oxidizing the fibers allows for better chemical bonding properties by the addition of oxygen atoms on the surface. This is can be done in multiple ways including, immersing the fibers in gases or liquids or by being electrolytically coated. After treating the surface, the fibers need to go through the sizing process. The fibers are coated with materials that are compatible with the adhesive used to make composite materials. These materials include nylon, polyester, urethane, epoxy and more. The last and final step is to roll up the sheets of carbon fiber onto cylinders called bobbins. This is how the fibers are twisted into various sized yarns.

Background Research

What is Carbon fiber? Carbon Fiber is a material consisting of, thin crystalline filaments of carbon, used as a strengthening material, especially in resins and ceramics. It is considered a reinforced polymer because it is mixed with other polymers to give it extra strength. Carbon Fiber goes back all the way to the late 1800`s where it was first discovered and created by Thomas Edison. Thomas Edison used the fibers as filaments for the light bulbs because they could withstand an incredible amount of heat and were great for conducting electricity. The Carbon Fibers at this time were cellulose-based materials such as bamboo or cotton. Later in 1950, high tensile strength carbon fibers were discovered and made with polyacrylonitrile. The benefit to using the newer fibers is that they are resistant to corrosion, fire and high stress tolerance. It is even resistant to its chemical inertness.

Resources

http://www.hj3.com/company/history-of-carbon-fiber/

-When it was discovered/by who

-what it was made of (1800)(1950)

- what is was used for

http://zoltek.com/carbonfiber/how-is-it-made/

-how its made

-materials in it

-different chemical processes

http://www.madehow.com/Volume-4/Carbon-Fiber.html

-background

-how its made

-composition

http://www.chm.bris.ac.uk/webprojects2002/mjames/chemistry.html

-tensile strength

-resistance to things

https://myorganicchemistry.wikispaces.com/Carbon+Fibre

-reinforced polymer

About the Author

Abe Stapleton is a junior at Billings Senior High School. He is enjoys being active and loves being outdoors. He is a 3 year letterman in wrestling, and is hoping to join the military after high school. Abe is full of energy and positivity. Although he may get sidetracked and distracted easily, he is a determined worker who always gives 100%in what he does.