Coefficient of Friction
The coefficient for dry GRAPHITAR® ranges from .04 to .25 depending on many factors. The addition of a lubricating fluid will reduce the coefficient of friction by a factor of 10 in many cases. Other operating factors which affect GRAPHITAR'S® coefficient of friction include: temperature, surface pressure, rubbing speed, mating material, surface condition and GRAPHITAR® Grade.
Flatness
GRAPHITAR® is exceptionally stable over a wide range of temperatures and chemical environments. GRAPHITAR® parts can be lapped by USG's production department to flatness tolerances of 3 helium light bands (.000033 inches variation over the entire lapped surface).
Porosity
High pressure air can be metered through GRAPHITAR® in air bearing applications: GRAPHITAR® can be used as a reservoir for lubricants or inks. The open porosity of GRAPHITAR® can range from about 20% down to a gas tight seal with a porosity of less than .01%. While some porous metals will react chemically with the medium with which they are filled, causing gumming and loss of porosity, GRAPHITAR® is not subject to this problem.
Composition
GRAPHITAR® is an engineered material. Its composition can range from all carbon to all graphite… and may include impregnants such as metals, resins or lubricants. Control over both compositions and processing variables permits GRAPHITAR® engineers to produce a remarkably consistent and reproducible product.
Thermal Conductivity
GRAPHITAR® is an excellent thermal conductor and is highly resistant to thermal shock. This characteristic is particularly important to jet engine seals, where temperatures can vary hundreds of degrees in a matter of seconds. The thermal conductivity of GRAPHITAR® ranges from 3 to 30 BTU/°F/SQ.FT/FT/HR. GRAPHITAR® closely approaches a true "black body" in its ability to radiate eat. This capacity, together with good thermal conductivity, makes a very useful combination for dissipating heat.
Electrical Properties
GRAPHITAR® is an electrical conductor and is non-magnetic. Its resistance ranges from .0005 to .0018 ohms per cubic inch. GRAPHITAR® has a negative resistance coefficient.