Silicone
also PDMS, LSR
Silicone rubber is a polydimethylsiloxane (PDMS) elastomer reinforced with fumed silica, supplied as liquid injection moulding LSR, milled solid HCR and RTV-2 casting systems.
Silicone grades and fills
Silicone is supplied in 15 conditions, soft to hard.
Compare all 15 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Sponge/Foam | Pick for low-closure-force weather seals, cushioning and insulation in enclosures and ovens. | 2 | 150 | 25 Shore A | |
Electrically conductive silicone | Pick for EMI gaskets, grounding pads and ESD-safe seals combining shielding with environmental sealing. | 3 | 120 | 20 Shore D | |
Thermally conductive (alumina / boron nitride filled) silicone | Pick for thermal interface pads, gap fillers and potting where heat must be moved but electrical isolation kept. | 3 | 120 | 18 Shore D | |
RTV-2 / Cast PDMS | Pick for prototyping molds, microfluidic PDMS chips, potting and encapsulation where no heated press is available. | 6 | 350 | 8 Shore D | |
soft grade | Pick for soft-touch skins, low-force seals, membranes and conformal cushions. | 7 | 650 | 6 Shore D | |
heat-stabilized (iron oxide / rare-earth) silicone, 250–300 °C capable | Pick for oven gaskets, exhaust/turbo seals, ironing and heater components where continuous service exceeds 200 °C. | 7 | 350 | 15 Shore D | |
flame-retardant silicone (UL 94 V-0) | Pick for rail, EV battery and appliance parts needing UL 94 V-0 with low smoke and halogen-free formulation. | 7 | 350 | 16 Shore D | |
soft-medium grade | Pick for baby-care parts, low-compression-force gaskets and flexible tubing. | 8 | 550 | 9 Shore D | |
HCR/HTV | Pick for extruded profiles, tubing, calendered sheet and low-volume compression-molded gaskets. | 8 | 400 | 15 Shore D | |
Fluorosilicone, fuel and oil resistant | Pick when silicone-level cold flexibility is needed together with resistance to fuels, hydrocarbon oils and solvents. | 8 | 250 | 16 Shore D | |
general purpose grade | Pick as the default all-round hardness for O-rings, keypads and static seals. | 9 | 450 | 12 Shore D | |
Liquid silicone rubber, 2-part platinum cure, injection molded | Pick for high-volume automated injection molding of thin, flash-free, dimensionally precise parts. | 9 | 550 | 12 Shore D | |
medium-hard grade | Pick for dynamic seals, grommets and parts needing better set resistance and extrusion resistance. | 9 | 400 | 15 Shore D | |
extra-hard grade | Pick for rollers, back-up rings and parts resisting extrusion under high clamp loads. | 9 | 220 | 30 Shore D | |
hard grade | Pick for high-pressure gaskets, valve seats and stiff overmolds. | 10 | 320 | 22 Shore D |
Supply forms, finishes and certifications
Ways Silicone is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Food Grade | FDA 21 CFR 177.2600 / LFGB / GB 4806.11 compliant | Certification |
Medical GradeDefault | Platinum-cured, USP Class VI / ISO 10993 LSR | Certification |
Optical | Optical Grade | Grade option |
What is Silicone?
Silicone rubber is a polydimethylsiloxane (PDMS) elastomer reinforced with fumed silica, supplied as liquid injection moulding LSR, milled solid HCR and RTV-2 casting systems. It runs continuously from −60 to 200 °C with UV and ozone resistance, physiological inertness and good electrical insulation, at about 8.5 MPa tensile and 550% elongation. Typical forms are moulded seals, tubing, keypads, food-contact parts and potting. Tear and abrasion resistance are low, oil and fuel resistance is limited outside FVMQ grades, steam and strong acid/alkali resistance is poor, and cost is above general-purpose rubber. Silicone has a density of 1.15 g/cm³ (0.0415 lb/in³), lighter than 57% of polymer grades. Its glass-transition temperature is -125°C (-193 °F). Silicone has a tensile strength of 8 MPa (1.16 ksi), weaker than 81% of polymer grades. Elongation at break is 500% and the elastic modulus is 0 GPa (3.19×10⁻⁴ Msi).
What is Silicone used for?
- O-rings and moulded gaskets
- Medical tubing and implant seals
- Keypads and button mats
- Baby bottle nipples and food-contact seals
- Electronic potting and encapsulation
- High-temperature oven and appliance seals
- Wire and cable insulation
Advantages
- Forms and bends easily — 95/100, better than 99% of polymer grades
- Good UV / weathering resistance — 97/100, better than 98% of polymer grades
- Polishes to a fine finish — 85/100, better than 92% of polymer grades
- Ductile — tolerates forming and impact — 500%, better than 90% of polymer grades
- High service temperature — 200°C (392 °F), better than 87% of polymer grades
Limitations
- Difficult to machine — 20/100, worse than 97% of polymer grades
- Low stiffness — 0 GPa (3.19×10⁻⁴ Msi), worse than 94% of polymer grades
- High mold shrinkage — 2.5%, worse than 93% of polymer grades
Silicone properties
Typical room-temperature values in the Medical Grade condition; bars are the position among polymer grades.
Physical5
Silicone has a density of 1.15 g/cm³ (0.0415 lb/in³), lighter than 57% of polymer grades. Its glass-transition temperature is -125°C (-193 °F).
Mechanical9
Silicone has a tensile strength of 8 MPa (1.16 ksi), weaker than 81% of polymer grades. Elongation at break is 500% and the elastic modulus is 0 GPa (3.19×10⁻⁴ Msi).
Thermal8
Silicone is rated for continuous service to 200°C (392 °F). It conducts heat at 0.22 W/m·K (0.127 BTU/hr·ft·°F), better than 60% of polymer grades. Thermal expansion is 270 µm/m·K (150 µin/in·°F).
Electrical7
Silicone is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 82% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of Silicone takes about 110 MJ of energy and emits 6.5 kg of CO₂ — more than 64% of polymer grades. Typical recycled content is 0%.
Manufacturability7
Silicone's machinability is poor (20/100, worse than 97% of polymer grades); weldability poor (20/100); formability excellent (95/100).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. Silicone is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Silicone
Is Silicone easy to machine?
Cured silicone is not conventionally machinable — use die cutting, waterjet, laser (with fume control) or cryogenic deflashing; sharp new blades and water lubrication prevent tearing.
Can Silicone be welded?
No thermal welding; join by uncured silicone adhesive, self-bonding primers, RTV, or oxygen-plasma bonding for PDMS microfluidics; secondary overmolding onto cured silicone requires primer.
Can Silicone be formed, bent or molded?
LSR: cold runner, 165–210 °C mold, 15–60 s cure, allow 2–3 % shrink and vacuum-vented tools; HCR: compression/transfer or extrusion + hot-air/steam cure; post-cure 200 °C/4 h to remove volatiles for medical/food use.
Manufacturability
The process limits FabDigit applies to Silicone. Every Silicone part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
Injection molding
| Mold shrinkage | — |
|---|---|
| Wall thickness | — – — |
| Recommended draft | — |
| Pre-drying | — |
Silicone chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| fumed silica (reinforcing filler)surface-treated, sets modulus and tear strength | 15 – 35 | 25 |
| hydride crosslinker (Si-H siloxane)addition-cure systems | 0.5 – 3 | 1.5 |
| platinum catalyst (Karstedt)peroxide (DCBP/DBPMH) used instead in HCR peroxide cure | 2×10⁻⁴ – 0 | 5×10⁻⁴ |
| extending filler / pigment / heat stabile.g. ground quartz, Fe2O3, Ce compounds | 0 – 15 | 5 |
| polydimethylsiloxane (PDMS) base polymermay contain vinyl-methyl and phenyl or trifluoropropyl substitution | ≥ 55 (balance) |
What surface finishes work on Silicone?
Surface finish is fully set by the mold (mirror EDM or texture); paints do not adhere without silicone-specific primer — use plasma/corona treatment, parylene or silicone inks; talc-free anti-block coatings for tack reduction.
Surface treatments FabDigit runs on polymer parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Injection Molding Coating
Metallization / Functional
Equivalent designations
Standards and trade names that resolve to Silicone in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- PDMSLSRLiquid Silicone
- Also called
- PolysiloxaneSI
How much does Silicone cost?
Silicone is a premium-cost polymer ($$$), cheaper than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Silicone — frequently asked
What is Silicone used for?
Silicone is typically used for O-rings and moulded gaskets, medical tubing and implant seals, keypads and button mats, baby bottle nipples and food-contact seals, electronic potting and encapsulation and high-temperature oven and appliance seals. In short: biocompatible soft silicone.
What is the tensile strength of Silicone?
Silicone has a typical tensile strength of 8 MPa (1.16 ksi) — weaker than 81% of polymer grades. Strength varies by condition: see the 15 listed tempers.
Is Silicone easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of polymer grades). Cured silicone is not conventionally machinable — use die cutting, waterjet, laser (with fume control) or cryogenic deflashing; sharp new blades and water lubrication prevent tearing.
Can Silicone be welded?
Not readily — weldability is rated poor (20/100). No thermal welding; join by uncured silicone adhesive, self-bonding primers, RTV, or oxygen-plasma bonding for PDMS microfluidics; secondary overmolding onto cured silicone requires primer.
What surface finishes work on Silicone?
Surface finish is fully set by the mold (mirror EDM or texture); paints do not adhere without silicone-specific primer — use plasma/corona treatment, parylene or silicone inks; talc-free anti-block coatings for tack reduction.
Can Silicone be formed, bent or molded?
LSR: cold runner, 165–210 °C mold, 15–60 s cure, allow 2–3 % shrink and vacuum-vented tools; HCR: compression/transfer or extrusion + hot-air/steam cure; post-cure 200 °C/4 h to remove volatiles for medical/food use.
What is the maximum service temperature of Silicone?
Silicone is rated for continuous use to about 200°C (392 °F), and briefly to 250°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Silicone cost?
Silicone is a premium-cost polymer ($$$), cheaper than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in Silicone?
Yes — Silicone is available for injection molding; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM D2000 — Classification System for Rubber Products (VMQ/FVMQ) — ASTM (2023)
- ASTM D412 / D624 / D395 / D2240 — tensile, tear, compression set, durometer — ASTM (2022)
- SILASTIC / Dow LSR and HCR product datasheets — Dow (2023)
- ELASTOSIL LR / R silicone rubber datasheets — Wacker Chemie (2023)
- Silopren LSR and thermally conductive silicone data — Momentive (2022)
- ASM Engineered Materials Handbook Vol. 2 — Engineering Plastics/Elastomers — ASM International (1988)
- CAMPUS / UL Prospector elastomer entries — UL / CAMPUS (2024)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.