Thermoplastic vulcanizates (TPV) are dynamically vulcanized alloys consisting mostly of fully cured EPDM rubber particles encapsulated in a polypropylene (PP) matrix. They 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. There are almost 100 grades in the S portfolio that are used globally in the automotive, household appliance, electrical, construction, and healthcare markets. The name Santoprene was trademarked in 1977 by Monsanto, and the trademark is now owned by Celanese. Similar material is available from Elastron and others.
Overview
TPV was created after several years of research and development aimed at finding new materials for injection-molded tires. Although the search for a new tire material was unsuccessful, it resulted in the development of TPV, which combines the characteristics of vulcanized rubber with the processing properties of thermoplastics. The first sales of developmental products began in 1977, the same 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 have a combination of elastomeric properties, like compression and tension sets, coupled with aging performance and chemical resistance.
Early successes
Santoprene TPV had 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.
Chemistry
Santoprene TPV is a dynamically vulcanized alloy consisting mostly of fully cured EPDM rubber particles encapsulated in a polypropylene (PP) matrix.
Photographs made using an atomic force microscope and a scanning electron microscope 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.
Properties
Designed for specific engineered applications, Santoprene TPV grades range from the hardness of 35 Shore A up to 50 Shore D.
Santoprene TPV grades offer the following: sealing performance: long-term aging durability combined with dimensional stability and physical properties over the life of the part; aesthetics: aspect harmonization between parts and comfort touch interior skins; processing: processability on standard thermoplastics processing equipment; design flexibility: suitability for coextrusion (coprocessing: molding, extrusion, blow molding) with other polymers for multipart system designs; weight reduction: lower density, part design optimization, and material replacement; recycling: fully recyclable within the manufacturing process.
Applications
Santoprene TPV grades are designed for a broad range of specific engineered applications.
Automotive components
Santoprene TPV (thermoplastic vulcanization) is used in weather seals, underhood and under-car applications, and interior components. In weather seals, TPV is used as a lightweight alternative to thermoset rubber materials in semi-dynamic and static parts, while in underhood and under-car applications it is well-suited for air ducts, tubing, molded seals, grommets, suspension bellows, cable jacketing, plugs, bumpers, and many other parts. This is due to its sealing performance and resistance to extreme temperatures, chemical exposure, and harsh environments.
Building and construction products
In commercial glazing seals, Santoprene TPV is used for curtain walls, storefronts, architectural windows, and skylight weather seal applications. It is also commonly used in residential glazing seals due to its low air and water infiltration ratings for the life of window and door systems.