Developing a strengthening bond to reinforce the material of choice for automotive window and door seals.
To address unmet customer needs for improved corner mold seals in automotive window and door weather seals., ExxonMobil decided to develop a new generation of thermoplastic vulcanizates (TPVs) offering better bonding to ethylene propylene diene monomer (EPDM) rubber, commonly used as a substrate, as well as a low coefficient of friction (COF), which is important for easy opening and closing of doors and windows.
Key to this initiative was finding new additive technologies to help deliver the enhanced performance ExxonMobil needed and meet certain conditions:
ExxonMobil wanted the new TPVs to deliver better surface finish, UV stability and good flow properties.
Santoprene™ TPVs from ExxonMobil Chemical have a long and successful track record as the materials of choice for flexible, high-quality corner mold seals.
Improve bonding performance with EPDM while lowering COF at the same time.
The DuPont team worked closely with ExxonMobil to help them meet their accelerated development timeline for the new TPVs. After reproducing the Santoprene TPV formulations using our silicone additives, we produced sample compounds internally so ExxonMobil could quickly move to the testing phase. The two teams took a flexible approach, with an open exchange of data and best practices, to expedite the process of narrowing the field to the formulations that are used today. As a result, the project took only three years – an unusually short development period.
This joint effort was a global undertaking, mirroring the worldwide reach of ExxonMobil.
Initial collaboration work done from the European headquarters of ExxonMobil
Pre-compounding work for testing was performed by DuPont in Europe
The project was later split among several ExxonMobil locations across the globe
The project experts found that synergies between a lower molecular weight silicone polymer and an ultra-high molecular weight silicone polymer delivered the low COF that ExxonMobil was looking for.
Importantly, a better COF would allow customers to eliminate a costly and time-consuming post-coating step previously needed to boost slip performance. While improving sliding properties vs. the organic additives used in the existing Santoprene TPV grades, the silicone technology also enhanced bonding performance to dense EPDM rubber, a critical property for overmolding.
Other key benefits of the new formulations include:
Higher flow for improved processing ease and throughput
Better abrasion resistance to protect against damage from slammed doors
Improved stability under UV light exposure to prevent cracking and discoloration