Platinum-cured vs peroxide-cured silicone
Decision rule of thumb
Pick platinum cure for any of: medical device, baby product, food contact, optical clarity, or any application where the part sits in prolonged contact with a body or a beverage. Pick peroxide cure when the part is a thick-walled industrial seal, the annual volume is in the low thousands, and the cost difference outweighs the post-bake. Add post-baking even for non-food contact when the part is in a confined space with a heat source — peroxide residues off-gas over years and can fog adjacent surfaces.
Cost and cycle-time delta
How to verify the cure system
Three signals on the supplier paperwork: 1. The TDS lists the cure system explicitly (addition cure or platinum cure for LSR, peroxide cure for HTV). 2. The certificate of compliance references either FDA 21 CFR 177.2600 with no post-bake requirement, or it states the post-bake cycle that was performed. 3. If the part is for infant oral contact (pacifier, teether, baby bottle nipple), the documentation should explicitly say no nitrosamine precursors or reference EN 14350 §6.3, which is the European limit on N-nitrosamine migration.
| Parameter | Platinum cure (LSR) | Peroxide cure (HTV) |
|---|---|---|
| Compound cost per kg | Higher | Lower (~30–50% less) |
| Cycle time | 30–90 s | 3–8 min |
| Post-bake | Not required | 200 °C × 4 h for food/infant |
| Extractables (aqueous) | Within 177.2600 limits as cured | Within limits only after post-bake |
| Shelf life of cured part | Indefinite | Indefinite after post-bake |
| Tool cost (single cavity) | Higher (cold runner) | Lower (compression) |
FAQ — platinum vs peroxide cure
Is platinum-cured silicone always better?
No. For thick-walled industrial seals in low volumes, peroxide-cured HTV is cheaper and good enough — the extractables only matter if the part is in prolonged contact with food, beverage or a body.
Can a peroxide-cured part be food-safe?
Yes, after a 200 °C × 4 h post-bake. The bake drives off peroxide residues and short-chain volatiles. Without post-baking the part usually fails the extractables limits in 177.2600.
Why is platinum cure called addition cure?
Because the crosslink forms by an addition reaction between vinyl-functional polymer and SiH crosslinker, catalysed by ppm-level platinum. No by-products, hence the low extractables.