Polyacrylonitrile

Polyacrylonitrile, often called PAN, is a synthetic, semicrystalline organic polymer resin. It is a substance made of long, repeating molecular chains. Most PAN resins are copolymers, which means they combine acrylonitrile with other molecules. This material is incredibly versatile because it can be transformed into many different forms. It can become soft fibers for clothing or extremely strong materials for aerospace engineering. Because of its unique chemical structure, PAN serves as a foundation for many modern technologies.

Creating high-quality carbon fiber from PAN involves a specific, two-step heating process. First, the PAN fibers undergo thermal oxidation. This means they are heated in the air at 230 °C to form an oxidized PAN fiber. The second step is called carbonization. In this stage, the fibers are heated above 1000 °C in an inert atmosphere, which is an environment without reactive gases. This intense heat removes non-carbon atoms and leaves behind a strong carbon structure. This process is essential because PAN is the chemical precursor for 90% of all carbon fiber production.

PAN can exist in several different forms depending on how it is made. It can be a homopolymer, which consists only of acrylonitrile units. It can also be a copolymer, where other molecules are added to change its properties. For example, modacrylics are a type of copolymer containing between 35% and 85% PAN. These are modified with halogen-containing molecules to increase flame resistance. Other versions, like those containing amidoxime groups, are used to treat metals because they can form complexes with metal ions.

The history of PAN is a complex story of discovery and international competition. Hans Fikentscher and Claus Heuck first synthesized the material in 1930 at the IG Farben works in Ludwigshafen, Germany. Early research stalled because the material was non-fusible, meaning it would not melt. It also would not dissolve in the industrial solvents used at that time. In 1931, Herbert Rein discovered that an ionic liquid called pyridinium benzylchloride could dissolve it. By 1938, the first PAN fibers were spun using special aqueous solutions.

Mass production of PAN did not begin until after World War II. In 1946, the American company DuPont started the first mass production run. They branded their product as Orlon. This occurred after German intellectual property was taken during Operation Paperclip. Meanwhile, in the German Democratic Republic, industrial production began in 1956 at the Agfa Wolfen plant. This work was done by a group called the "Wolcrylon" collective. Their achievements in the field earned them the GDR's National Prize II Class for Science and Technology.

Today, PAN is used in a massive variety of high-tech and everyday applications. Carbon fibers made from PAN are used in 20% to 25% of the airframes for Boeing and Airbus wide-body aircraft. You can also find PAN derivatives in missiles, rocket motors, and pressure vessels. In your daily life, PAN is often found in items labeled as "acrylic." These fibers are used for socks, sweaters, tents, and even bicycle frames. While carbon fiber is expensive at roughly $15 per pound, the material remains essential for its high strength and low density.

Beyond textiles and aerospace, PAN connects to many other scientific fields. In electrochemistry, heat-treating PAN blocks under high pressure creates glassy carbon. This material is a common electrode because it has excellent conductivity. PAN is also used to create ion exchange resins through a process called hydrolysis. These resins are useful for removing metal ions like calcium and magnesium from liquids. From the clothes on your back to the planes in the sky, PAN is a fundamental building block of modern material science.