Santoprene

Thermoplastic vulcanizates (TPV) are part of the thermoplastic elastomer (TPE) family of polymers, but are closest in elastomeric properties to EPDM thermoset rubber, combining the characteristics of vulcanized rubber with the processing properties of thermoplastics. TPV is a dynamically vulcanized alloy consisting mostly of fully cured EPDM rubber particles encapsulated in a polypropylene (PP) matrix. There are almost 100 grades in the Santoprene TPV product portfolio which are used globally in the automotive, household appliance, electrical, construction and healthcare markets. ExxonMobil is the sole proprietor of the material.

TPV was created following several years of research and development to find a new material for injection molded tires. While this search for a new tire material was unsuccessful, it led to the development of TPV, which combines the characteristics of a vulcanized rubber with the processing properties of thermoplastics. The first sales of developmental products were in 1977, the year it was registered by Monsanto, and it was fully commercialized in 1981.

Part of the TPE family of polymers, TPV is the closest in elastomeric properties to EPDM thermoset rubber. TPVs offer a combination of elastomeric properties, like compression and tension set, coupled with aging performance and chemical resistance.

Santoprene TPV enjoyed early application successes in the automotive sector, including rack and pinion boots, due to its flex life, fluid resistance and sealability. In the appliance sector, a dishwasher sump boot made with Santoprene TPV provided good sealing and resistance to heat and fluids. Due to its sealing properties, Santoprene TPV was also successful in the domestic and high-rise construction sectors in applications such as window seals, caster wheels, tubing and small hose parts, electrical connectors and coatings for wire and cables. It was also used in the medical industry as a gasket on syringe plungers.

Santoprene TPV is a dynamically vulcanized alloy consisting mostly of fully cured EPDM rubber particles encapsulated in a polypropylene (PP) matrix.

These photographs, made using an atomic force microscope (on the left) and a scanning electron microscope (on the right), show a multitude of very small particles, typically no bigger than a couple of microns in diameter. These particles are fully vulcanized rubber (typically EPDM rubber for most Santoprene TPV grades) in a thermoplastic phase (most often PP in the case of Santoprene TPV grades). Fully cross-linked or vulcanized means 98% or above and because the morphology is “locked-in,” it provides stable physical properties.

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