Platinum-cured silicone and TPE are the two default choices for soft parts that contact skin, and the choice is usually made on price. This guide compares them on the properties that decide whether the part still performs after a year of use.
Cure system and what it leaves behind
Platinum silicone is cured by an addition reaction with a platinum catalyst, which produces no by-products. Peroxide silicone, a cheaper variant, decomposes during cure and needs a post-cure oven cycle to drive off the by-products, or the part carries an odour and a higher level of extractables.
TPE is a thermoplastic elastomer, which means it is not cross-linked at all: it is a melt-processed compound, usually SEBS or TPU, that behaves like rubber because of its physical structure rather than chemical bonds. This has a direct consequence: TPE softens with heat and can deform under sustained load, where silicone holds its shape.
The comparison
| Property | Platinum silicone | TPE (SEBS based) |
|---|---|---|
| Processing | Thermoset, LSR injection | Thermoplastic, standard injection |
| Cycle time | Longer, cure is time-bound | Shorter, cools in the tool |
| Temperature range | -50 to +200 C | -40 to +100 C typical |
| Compression set | Low, holds shape under load | Higher, creeps under sustained load |
| Chemical resistance | Excellent, resists most oils and cleaners | Good, attacked by some oils and solvents |
| Hand feel | Dry, powdery, premium | Tacky, rubbery, softer |
| Transparency | Available, clears well | Available, yellows with age |
| Autoclavable | Yes | Generally no |
| Material cost | Higher | Lower |
Where the cost difference actually lands
TPE is cheaper per kilogram and moulds faster, so the part price is lower. But the cycle-time advantage shrinks on thin-walled parts, where the silicone tool can run more cavities, and the tooling cost is comparable. On a high-volume part with a straightforward geometry, TPE wins on price. On a part that must hold a seal under sustained compression, or that must survive a hot car or a dishwasher, silicone wins on warranty cost.
Lifespan and failure modes
- Silicone fails by tearing, usually at a stress concentration introduced at the gate, and by surface degradation under prolonged UV exposure. It does not creep, so a silicone seal that is tight on day one is tight in year five.
- TPE fails by taking a permanent set, which is why a TPE gasket compresses flat and never recovers, and by stress cracking where it contacts certain oils. It also picks up dirt because the surface is tackier.
Choosing
- Sealing and gasket functions under sustained load: platinum silicone.
- Grip and soft-touch surfaces that are not load-bearing: TPE, with a hardness chosen against the drop test.
- Parts that will be washed repeatedly or autoclaved: platinum silicone.
- Parts that must be transparent and stay clear: platinum silicone.
The overmoulding question is separate: TPE bonds chemically to ABS, PC and PC/ABS substrates in a two-shot process, while silicone bonds to almost nothing without a primer. A TPE grip on an ABS housing is a standard two-shot; the same grip in silicone needs an adhesive layer and a different tool.
Related reading
Our TPE overmould programme covers the two-shot bonding route, and the platinum LSR programme covers the sealing application.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
