Platinum Cured vs Peroxide Cured Silicone: Which Grade Does Your Part Need?
Both are silicone rubber, and on a drawing they look identical. The cure system decides what leaches out of the part — and that decides whether it belongs in a food line or on a machine frame.
What the cure system actually changes
Silicone starts as the same polymer either way. The difference is how the chains are locked into a network. Peroxide curing uses heat to split a peroxide into radicals that grab methyl groups; platinum curing uses a catalyst to add Si–H across a vinyl group. Same base gum, two very different leftovers.
That leftover is the whole story. Peroxide curing leaves volatile fragments behind, and those fragments migrate. In a food line or under a patient’s skin, migration is the exact thing you are trying to prevent.
Side by side
| Property | Peroxide cured | Platinum cured |
|---|---|---|
| Catalyst residue | Peroxide fragments, partly volatile | None — consumed in the reaction |
| Odour and taste | Noticeable, worse without post-cure | Neutral after proper post-cure |
| Transparency | Translucent to hazy | Water clear |
| Compression set | Good | Typically 15–25% lower |
| Relative cost | Lower | Higher — catalyst and clean handling |
| Typical use | Industrial seals, general extrusion | Medical, food contact, pharma |
Where each one wins
If the part touches nothing but machine oil and daylight, peroxide curing is the economical answer and there is no reason to pay a premium. Industrial gaskets, weather seals and general extrusions live there comfortably.
The moment a part touches food, drinking water, a drug product or a patient, platinum becomes the default. Extraction limits and odour panels are where peroxide compounds fall over — not in the tensile numbers.
How to specify it so you get what you asked for
- Name the cure, not the family. Write “platinum cured, post-cured 4 h at 200 °C” rather than “silicone”.
- Ask for extractables data. “FDA approved silicone” is a phrase with no legal meaning; a test report with numbers is what counts.
- State the post-cure. Residual volatiles are the usual cause of a failed smell or taste panel.
- Add your sterilization cycle. Gamma and steam stress the compound in different ways, and the answer changes the formulation.
The cost conversation
Platinum compounds typically run 20–35%% higher on material cost. On a 6 mm tube that is cents per metre. On a large moulded part it moves the quote meaningfully — which is why the question belongs at the drawing stage, not after the tool is cut.
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Questions about your own part?
Send a drawing or a sample. We will tell you which compound and hardness we would run, and what it costs at your volume.