Overview
TPV (thermoplastic vulcanizate) is the elastomer designed to displace thermoset EPDM rubber in production. The chemistry is straightforward: fully-cured EPDM rubber particles dispersed in a continuous polypropylene matrix. The composite behaves like vulcanized rubber because the EPDM particles are crosslinked, but it processes like a thermoplastic because the PP continuous phase melts and flows.
The commercial story is about manufacturing economics, not material performance. Versus thermoset EPDM:
- ~70% lower capital investment (no compounding mill, vulcanizing press, demold/trim/finish line)
- ~50% lower energy consumption in part production
- ~30% lower part weight (TPV density 0.95 vs EPDM 1.2)
- Full in-stream recyclability — scrap is reground and remolded
- Tighter dimensional tolerance — net-shape molding vs vulcanized rubber’s high shrink and difficult trim
- Faster cycles — seconds per part vs minutes per vulcanization
The compromise: TPV is somewhat softer (more compression set), has a softer continuous phase that limits high-temperature performance to ~135°C, and is more expensive per pound than basic EPDM compound. Total system economics favor TPV in nearly all automotive sealing applications, which is why ExxonMobil’s Santoprene has displaced EPDM rubber as the default for glass run channels and weatherstrip across the global automotive industry.
The Santoprene grade nomenclature
ExxonMobil’s Santoprene naming convention is information-dense. Reading “Santoprene 101-64”:
- 101 — series number (general-purpose black)
- 64 — Shore A hardness
Series numbers indicate intended application family:
| Series | Application |
|---|---|
| 101 | General-purpose, black |
| 201 | General-purpose, natural / colorable, UV-stabilized |
| 111 | Flame-retardant, halogen-free V-0 |
| 121 | Automotive glass run channel — flocked-surface compatible |
| 191 | Automotive interior sealing |
| 251 | Food contact, NSF/ANSI 51 / 61 |
| 8000 | Medical / pharmaceutical, USP Class VI, steam-sterilizable |
The numerical suffix is always Shore A hardness, which lets you spec a part by application series + hardness in a single number: “Santoprene 201-73” means UV-stabilized colorable TPV at 73 Shore A.
How TPV actually works — dynamic vulcanization
TPV is manufactured by dynamic vulcanization — a process in which the EPDM rubber and polypropylene are mixed together while the EPDM is being crosslinked. The result is millions of micron-scale crosslinked rubber particles uniformly dispersed in the molten PP.
When the composite is later injection-molded:
- PP continuous phase melts and flows (the part is “thermoplastic”)
- EPDM particles remain crosslinked and do not melt (the part is “vulcanized”)
- After solidification, the EPDM particles provide elastomeric recovery; the PP holds the shape
This structure explains TPV’s specific failure modes — the PP phase softens above 110°C (limit on hot service), and the PP phase swells in aromatic solvents and oils (limit on chemical compatibility, hence the existence of Geolast with NBR particles in PP for oil contact).
Variant guidance — which TPV grade
- Santoprene 101 series (black) — pick for general industrial, underhood automotive, and any application where black is acceptable and color matching doesn’t matter.
- Santoprene 201 series (natural) — pick for visible exterior trim, consumer products, and color-matched sealing.
- Santoprene 121 / 191 (automotive sealing) — pick for glass run channels and door/trunk weatherstrip; flocked-surface compatible.
- Santoprene 8000 series (medical) — pick for peristaltic pump tubing in dialysis, biopharmaceutical, and IV applications.
- Geolast (NBR/PP) — pick for oil-contact and fuel-contact applications where standard Santoprene swells.
- Santoprene FR / 111 series — pick for cable jacketing in transit-rail and infrastructure requiring halogen-free UL94 V-0.
- Food / drinking water (251 series, similar) — pick for NSF/ANSI 51/61 compliance in food and beverage equipment.
Machining notes — TPV is not a machinable material
TPV is fundamentally a soft elastomer reinforced by a thermoplastic matrix; conventional CNC machining is impractical. The workpiece deforms under any cutter pressure, surfaces smear, and tool wear is not the limiting factor — workpiece dimensional control is.
Practical TPV fabrication:
- Net-shape injection molding or profile extrusion — the intended manufacturing routes.
- Waterjet cutting for sheet stock.
- Die-cutting for thin sheet gaskets and seals.
- Grinding for surface finishing.
- Co-injection / over-molding onto polypropylene substrate — the standard assembly route. TPV bonds tenaciously to PP without adhesives because the PP continuous phase fuses with the PP substrate during molding.
For prototype work where machining is the only option, cryo-machining (LN2 cooling) of harder Shore A and Shore D grades is possible but rarely justified — net-shape prototype tooling is cheaper.
Failure modes worth designing around
Polypropylene phase softening above 110°C is the dominant service-temperature failure. The PP continuous phase loses stiffness above its melting transition; TPV’s elastomeric recovery falls off. Above 135°C, standard Santoprene loses meaningful elastomer behavior. For continuous high-temperature service, use silicone (LSR) or thermoset EPDM.
Oil swell on standard Santoprene — the PP phase swells in mineral oils and aliphatic solvents. Geolast (NBR/PP) is the oil-resistant alternative; standard Santoprene is fine in dry service but swells in fuel and oil contact.
Compression set under sustained load — TPV recovers from short-term compression but acquires permanent set under prolonged load. Static seals lose contact stress over years. Specify low-CS grades or design with cyclic dynamic motion.
Equipment contamination — Santoprene is incompatible with acetal (POM) and PVC on shared processing equipment. POM contamination causes severe degradation; PVC contamination causes HCl-driven destruction. Dedicated tooling required.
UV degradation on standard grades — surface chalking and crazing on outdoor exposure. UV-stabilized 201 series for weatherable applications.
Applications by industry
- Automotive sealing — the dominant application by volume. Glass run channels, door/trunk/hood weatherstrip, exterior body trim, belt-line seals, sunroof seals. Santoprene has displaced EPDM in OEM specifications across Ford (WSD-M2D379), GM (GMW15813), Chrysler/Stellantis (MS-AR-100), VW Group, Toyota, and Japanese/Korean/Chinese automakers.
- Medical / pharmaceutical — peristaltic pump tubing for hemodialysis (Fresenius, Baxter), biopharmaceutical fluid handling, IV pump tubing. Santoprene 8000-series and Pharmed BPT are the standard elastomers in these applications.
- Appliances — washing machine door seals, refrigerator gaskets, dishwasher tubing, dryer seals. Replaces older EPDM and silicone seals at lower cost and weight.
- Construction sealing — window and door weatherstrip, glazing seals, expansion joints. Replaces silicone and EPDM in cost- sensitive applications.
- Food and beverage — NSF/ANSI 51 and 61 compliant tubing for dispensers, brewing equipment, food-processing fluid handling.
- Wire and cable — outdoor and industrial cable jacketing where flexibility, weather resistance, and oil resistance combine. FR variants for transit and infrastructure.
- Consumer products — soft-touch over-molds on tool handles, toothbrush grips, sports equipment grips, and similar PP-substrate assemblies. TPV’s clean bond to PP without adhesive is the assembly advantage.
- Industrial fluid handling — peristaltic pump tubing for chemical metering, drinking water dispensing, low-pressure hydraulic seals.
- Bellows and protective boots — CV joint boots, actuator protective covers, machine-tool way covers.