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.