Carbon fibers based on polyacrylonitrile (PAN) were developed in the 1960s by Dr. Akio Shindo at the Agency of Industrial Science and Technology in Japan.  The resulting fibers contained 55% carbon. Pan is used to make carbon fiber reinforced plastics.

In fact, the PAN-based conversion process quickly became the primary method for producing carbon fiber.  Ninety percent of carbon fibers today are made from polyacrylonitrile (C3H3N)n  or PAN a synthetic, semi-crystalline organic polymer resin. But the remaining 10% are made from rayon or petroleum pitch. Fibers made from PAN are extremely strong and light. These carbon fibers are bound by thermoset or thermoplastic polymers such as polyester, vinyl ester, or nylon to make carbon fiber reinforced plastics or carbon FRP.

Adding Carbon Fiber To A Polymer Has Many Benefits

Tensile strength and flexural modulus increase when carbon fiber is added as is the heat deflection temperature or HDT.  Additionally, adding carbon fiber reinforcement diminishes shrinkage and warping.

Each carbon fiber is a long thin strand made up of thousands of carbon filaments. So a single fiber is about 5-10 μm in diameter and composed mostly of carbon.  Microscopic crystals in the carbon bond together in a structure that is more or less aligned parallel to the long axis of the fiber.  And it is this alignment of crystals that makes the fibers so strong.

Classified By Tensile Modulus

Carbon fibers are classified by the tensile modulus* of the fiber.  The tensile modulus may range from 34.8 million psi to 72.5-145.0 million psi.  However, steel has a tensile modulus of 29 million psi. Thus the strongest carbon fiber is five times stronger than steel.

“Low” modulus fibers have a tensile modulus below 34.8 million psi (240 million kPa). Fibers are also classified in ascending order of tensile modulus as “standard modulus,” “intermediate modulus,” “high modulus,” and “ultrahigh modulus.” Carbon fibers with a classification of ultrahigh modulus have a tensile modulus of 72.5-145.0 million psi (500 million-1.0 billion kPa).

Spinning, Stabilizing, Carbonizing, Surface Treatment, And Sizing

The manufacturing process for carbon fiber is partly chemical and partly mechanical. 

A few products made from carbon fibers are fishing rods, bicycles, golf equipment, tennis rackets, and parts for aircraft, bridges, and automobiles.

*Tensile modulus is how much pulling force a fiber of a certain diameter can exert without breaking. Tensile modulus is described by pound per square inch or psi.

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  1. February 26, 2024

    Can carbon fiber materials be used in injection molding processes?

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