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.
Available through
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
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