What is the difference between asbestos and non-asbestos gaskets?
One gasket type contains asbestos as a reinforcing fiber while the
other does not. As a reinforcing fiber, asbestos is strong, can
withstand high temperatures and chemical attack, and is relatively
cheap compared to many other materials. The physical properties that
make asbestos an excellent gasket fiber also make it a hazardous
substance to work with.
Asbestos fibers are long, thin and extremely small. Exposed fibers
easily shred into thin needle-like strands that can drift in the air
and be inhaled. The fibers lodge deep in the lungs where their sharp
needle-like presence becomes a source of constant irritation. Over
time, the accumulation of asbestos fibers can lead to a variety of
lung ailments, including cancer.
Because of that, the government has tried to ban asbestos. A court
ruling has put the proposed ban on temporary hold. Even so, all
domestic gasket manufacturers are now using non-asbestos materials
in their U.S. gasket plants. Asbestos is still being used by
offshore manufacturers and is still found in many import
applications.
The asbestos hazard is only a concern to those who work in the
asbestos handling and processing industries, including companies
that supply gasket manufacturers with rolls of gasket facing
material and paper.
Once fibers are encapsulated in the filler material used to make
gaskets, they cannot escape and pose no significant health hazard to
those who work in gasket manufacturing plants, the distribution
system, or installers.
Most domestic gasket manufacturers today use a proprietary mix of
non-asbestos reinforcing fibers to produce gaskets equal to or
better than asbestos gaskets they used to make. One type of fiber
being used is aramid fiber (Kevlar), which is two to nine times
stronger than asbestos.
Kevlar lacks the temperature resistance of asbestos and cannot be
used on exhaust manifolds or certain head gasket applications.
Kevlar also costs a lot more than asbestos. The amount of Kevlar
typically used in an asbestos-free gasket material is usually no
more than 10%.
Expanded graphite is another material being used in place of
asbestos. Graphite is an excellent conductor of heat and can easily
handle temperatures as high as 1,800 degrees F. It is ideal for high
heat applications such as exhaust manifolds and head gaskets in
diesel and high output engines. Graphite is also a natural
lubricant, making it well suited to engines with cast iron blocks
and aluminum heads. Like Kevlar, graphite is expensive.
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