This technical information has been contributed by
ExxonMobil Chemical

New TPV Database Improves Part Design, Reduces 'Over-engineering'

Rubber Thermoplastic Extrude Mold

HOUSTON, Tex.--ExxonMobil Chemical recently introduced a new design tool that can help engineers predict the long-term behavior of SantopreneTM thermoplastic vulcanizates (TPVs). The new "compression stress relaxation database" helps predict how Santoprene TPVs perform initially, and then at any time during the expected life of the part. Engineers can use the information to create more effective designs that improve part reliability while reducing material use and costs.

Without this type of data, engineers have typically applied arbitrary safety factors to their designs to account for diminishing performance caused by stress relaxation over time. Because these safety factors are estimated, parts are often over-engineered to ensure that they don't fail. The result, according to the company, is increased material use and costs.

The database provides design engineers with more confidence as it helps them to ensure that the part will meet the specified performance requirements of the application.

"This set of data is particularly important in applications like seals, as in time, the material will relax and creep, causing a predictable decline in performance," said Ward Narhi, senior design engineer, ExxonMobil Chemical's Santoprene specialty products. "To achieve an effective design, it is important to have a good understanding of the material's long-term behavior."

When designing a seal, an engineer must know the level of sealing required at the beginning of its life, which can be calculated using finite element analysis (FEA) or determined through prototype testing. From there, the new database helps to accurately plot the long-term performance of the material at any point in the future. This compression stress relaxation data is available at different temperatures (23°C, 70°C, 80°C, 100°C and, for some grades, minus 40°C) for the Santoprene TPV sealing grades used in pipe, automotive, construction, and general-purpose applications.

"The new database enables engineers to 'design smart,' helping them to eliminate over-engineering, improve part reliability, and lower costs," said Narhi. "This database can be particularly valuable in automotive applications, where less material can result in lower weight, leading to reduced fuel consumption."

Designers can access the free database and detailed instructions on how to use it online at The database can also be used to compare different materials to determine which offers optimum long-term performance for specific applications.

For more on ExxonMobil Chemical, visit

Santoprene is a trademark of an Exxon Mobil Corporation affiliate.

This technical information has been contributed by
ExxonMobil Chemical

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