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| | When it comes to Rubber Gaskets and Seals,
Material Matters...a Lot
by Phil Maxwell June 2005
Know What You're Buying
Elastomers or rubber compounds come in a wide variety of material types and brands, and are used in
a broad array of applications. Most of the critical properties relating to performance
and longevity can't even be measured outside a laboratory. Yet, those differences can be huge in terms of seal performance or failure, as well as longevity.
Nearly all rubber gaskets and seals are destined to fail in time due to the natural breakdown of the unique elastomeric molecular bond of rubber when stressed (e.g. compressed, elongated), as rubber seals are normally intended to be. Users interested in rubber that will effectively seal for as long as possible actually want gaskets or seals made of higher quality rubber, which is only discernible through laboratory tested physical properties like tensile strength, ultimate elongation, and abrasion resistance. A little information, therefore, can translate into considerably better seal performance, longevity, and overall costs.
One problem is that rubber manufacturers and vendors define their products in
terms of chemical compound groups and measurable physical properties, not by how
suitable they are for any particular application. This puts the
brunt of design responsibility on the end-users, and, at least by implication,
places the burden of providing the information on suppliers,
though few seem to readily accept that responsibility.
Unfortunately, most internet dealers don't even state the properties of their
products in any way that guarantees their quality. Many even give comprehensive information on rubbers in general, effectively masking the lack of
published specifications for their own products to all but search engine spiders that don't know the difference. Don't let numerous
charts, graphs, images, and articles fool you: If they don't specifically
state the physical properties of their products (not general rubber properties) with tolerance ranges, they
aren't saying anything about their products. In most
cases, customers have no assurance whatsoever that they aren't getting o-rings or some other rubber product
barely qualifying as "Buna-n rubber," for instance, and nothing more.
If they simply state properties like durometer, tensile strength, and elongation
without tolerances (i.e. +/-, min, max, or range), it doesn't necessarily mean
their products meet those values; it only means...well, it doesn't really mean
anything.
We assume that most internet dealers and rubber product manufacturers are reputable
companies that wouldn't knowingly sell sub-standard materials, though it is also
true that there's money to be made through cheapening rubber compounds,
especially as the internet fuels greater competition.
The combination of distributors who can and do sell o-rings and other rubber gaskets and seals with unspecified
properties and manufacturers competing for their business invites circumstances
that naturally ends with users getting sub-standard rubber products without even realizing it...at
least before they fail well short of their time.
The bottom line isn't to insinuate that unspecified properties necessarily
indicates sub-standard quality. Rather, we aim to emphatically illuminate the fact that
standard commercial rubber sealing products should not be bought without basic physical property specifications, since that is the only way a user can measure the otherwise invisible, but significant quality features hidden within the rubber.
Phil Maxwell is Vice-President and General Manager of Metro Industries, Inc. (aka Standard Gasket Products), a Kansas City, Missouri, based distributor of o-rings and other standard rubber gasket and sealing products.
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Material Does Matter
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