New pitch-based carbon fibers are said to have higher   modulus or stiffness than conventional carbon fibers.

New pitch-based carbon fibers are said to have higher modulus or stiffness than conventional carbon fibers.


Houston. . . . Conoco Inc. has developed a new pitch-based carbon fiber for use in plastics, carbon composites, carbon-carbon systems, batteries, and cement structures. The material is intended for automobiles, telecommunications, electrical systems, and construction material. Twelve years in the making, the carbon fiber will be manufactured using several Conoco carbon-upgrading processes. Carbon upgrading takes lower-value feedstocks and engineers them into higher-value products such as lubricants, specialty graphite, and now, carbon fibers.

Other types of carbon fibers such as Rayon and PAN (polyacrylonitrile) are made from higher-cost chemical intermediaries — primary polymers. Others are made from isotropic pitch that comes from lower-cost petroleum or coal-tar feedstocks. In the past, more economical isotropic pitch fibers did not provide a sufficiently broad range of properties.

The Conoco carbon fiber is made from a higher performing petroleum pitch called mesophase. The word "mesophase" means liquid crystal. The ordered, molecular liquid-crystal structure, fossilized in fiber form, is said to yield fibers with higher performance than isotropic pitch.

Much the way different grades of steel perform depending on structure and heat treatment, pitch and PAN carbon fibers have properties that suit different applications. The most common carbon-fiber type is PAN. It is primarily for structural reinforcement because of its high tensile strength. Mesophase pitch fibers, on the other hand, offer designers a different profile. They are easily customized to meet specific applications. They often have a higher modulus, or stiffness than conventional PAN fibers, are intrinsically more pure electrochemically, and have higher ionic intercalation. Mesophase pitch fibers also are said to possess higher thermal and electrical conductivity, and different friction properties.

Preliminary properties for standard modulus grade carbon fibers

PROPERTY

TYPICAL VALUES
Fiber diameter, µm
11.1
Tensile strength, ksi
250
Modulus, Msi
30
Fiber real density, gm/cm 3
1.96
Bulk volume density, gm/cm 3
0.0193
Bulk area density, gm/m 2
670
Carbon content, %
98

Preliminary properties for battery-grade carbon fibers
PROPERTY
TYPICAL VALUES
Fiber real density, gm/cm 3
2.19
Carbon content, %
>99
Volume electrical resistivity, –cm
223
Volume electrical conductivity, –1 –cm–1
0.00448

Surface area, m2/gm

<1(0.33)

Conoco Carbon Fibers, Box 2197, Houston, TX 77252, (281) 293-4002, www.carbonfiber.conoco.com