ExxonMobil Chemical has developed a novel approach for formulating Vistalon EPDM compounds for automotive sponge weatherseals. Combining an amorphous, high-diene Vistalon EPDM rubber with a propylene-based elastomer, ExxonIT0316, produces a compound that can help to reduce the density of the sponge profile, while controlling the key attributes that meet automotive weatherseal specifications for automakers.
“Using this new approach to tailor EPDM rubber compounds allows customers to reduce part cost while broadening their range of sponge profiles with differentiated properties,” said Thierry Hombert, global market development manager, Specialty Elastomers and Butyl business, ExxonMobil Chemical.
Vistalon EDPM rubber is widely used for automotive exterior-sealing systems, especially sponge weatherseals around the doors, trunk and hood. Due to its air and ozone resistant properties, it insulates against water, dirt and noise over the lifetime of the vehicle.
The new formulation, based on metallocene polymerization technology, provides an opportunity to design high-performance compounds with tailored properties through the precise control of the molecular architecture and co-monomer introduction. Tests on a semi-industrial ultra high-frequency (UHF) extrusion line show that blowing-agent efficiency is optimized without compromising the sealing properties of the sponge profile. The compression load deflection (CLD) and compression set (CS) are maintained, and density can be reduced by 10 %, which provides the potential to reduce costs. The uncured, soft-sponge compound also exhibits more green strength, improving weatherseal handling.
Compounders can tailor the performance of the sponge weatherseal to produce a profile that has a similar density to an EPDM compound but with a higher CLD or a profile with a lower density but a similar CLD.