Elastomer
Silicone (LSR)
Wide temperature range, biocompatible, and molded as a thermoset.
Published values for unfilled grades at 23 °C unless stated. Confirm against the supplier datasheet for the grade you specify.
What it is
LSR is a two-part platinum-cured silicone injected cold into a hot tool, where it cures in seconds. Unlike thermoplastic elastomers it is a true thermoset, so it does not soften with temperature and it holds its properties from −50 °C to 200 °C.
It is the standard elastomer for medical and food applications because it is biologically inert, steam sterilizable, and available with full ISO 10993 and USP Class VI documentation.
Where it is used
- Medical seals, valves, and patient-contact components
- Baby and food contact products
- Automotive and appliance seals in hot locations
- Keypads and membranes
- Electrical insulators and cable seals
Processing notes
The tool runs hot, 160–200 °C, and the material runs cold. That is the opposite of thermoplastic molding and needs a dedicated machine and cooled shut-off nozzle.
Viscosity is very low, so tools must be built with tighter shut-offs than thermoplastic tools or the material will flash.
Post-cure at 200 °C for 4 hours removes volatiles for medical and food parts.
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Design notes
Shrinkage is high, 2–3.5 %, and depends on cure and part geometry. Expect a tool correction after first samples.
Deep undercuts can often be stripped because the material is so elastic.
Overmolding onto thermoplastics needs a primer or a self-bonding grade; not all substrates survive the tool temperature.
Grades and variants
- General purpose 30–70 Shore A
- Medical grade with ISO 10993 / USP Class VI
- Food contact grades, FDA and EU 1935/2004
- Self-bonding grades for overmolding
- Optical grade LSR for lenses and light guides
Alternatives
If Silicone (LSR) is not the right answer
See the full Silicone vs TPE comparison, spec by spec.
Specifying this material?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.