Silicone Rubber Specifications
This page lists the specifications we hold for custom silicone parts. It covers our reference material grades, dimensional tolerances, process capabilities, and the test methods behind each figure.
Every value here comes from a measured material datasheet or a documented shop limit. Where we do not hold a value, we say so.
Reference Material Grades
These are our standard compression grades. The values are measured, not nominal. Test methods are listed under the table.
| Reference grade | Shore A | Density g/cm³ | Tensile MPa | Elongation % | 100% modulus MPa | Tear kN/m | Compression set % | Rebound % |
|---|---|---|---|---|---|---|---|---|
| Standard HCR 30 | 30 | 1.09 | 10.0 | 900 | 0.40 | 25 | - | - |
| Standard HCR 50 | 50 | 1.13 | 11.0 | 600 | 1.25 | 28 | - | - |
| Standard HCR 70 | 70 | 1.20 | 10.0 | 450 | 2.70 | 25 | - | - |
| Low-compression-set HCR 50 | 50 | 1.14 | 8.8 | 412 | 1.35 | 12 | 9 | 64 |
| High-tear HCR 70 | 69 | 1.19 | 11.0 | 619 | 3.10 | 48 | - | 44 |
| Fluorosilicone 70 (FVMQ) | 70 | 1.44 | 10.0 | 230 | - | 15 | 25 | - |
Methods: density per ISO 2781. Hardness per ASTM D2240. Tensile strength, elongation at break, and 100% modulus per ISO 37 Type 2. Tear strength per ASTM D624. Compression set per ASTM D395 B. Rebound per ASTM D7121.
We run hundreds of grades across these families. These six are our reference grades. We match the exact grade to your part during DFM, and we send its datasheet before tooling.
Material Families and Capability Ranges
Each material has its own range. We name the material on every range so the number is not read as a general silicone limit.
| Material | Durometer | Temperature | Notes |
|---|---|---|---|
| HTV solid silicone | Shore A 10 to 80 | -50 to +200 °C continuous, about 230 °C short peak | Peroxide cure or platinum cure |
| LSR | Shore A 10 to 80 | Per grade | Runs through our partner |
| VMQ silicone | Per grade | Material service range -55 to +250 °C | High temperature work |
| FVMQ fluorosilicone | Per grade | -60 to +200 °C | Fuel and oil resistance |
| Extrusion grades | Shore A 30 to 80 | Per grade | Tubing, cord, and profiles |
Custom compounds can extend heat resistance to about 300 °C, stated per grade. See how silicone handles high heat for the full temperature picture.
Silicone base stocks come from premium European and US suppliers, plus qualified domestic partners.
Other rubbers come from a 32-compound library, including FKM, EPDM, NBR, HNBR, CR, CSM, IIR, and NR. We do not run TPU. For the full grade list, see silicone types and cure systems.
Dimensional Tolerances
These are the tolerances we hold on a standard job.
| Feature | Tolerance |
|---|---|
| Mold machining | 0.03 mm |
| Finished part, standard | ±0.2 mm |
| Finished part, minimum | ±0.1 mm |
| Thinnest silicone wall | 0.5 mm |
| LSR, partner process | ±0.05 to 0.15 mm |
| Cord and extrusion | ±0.5 mm at 50 mm |
Many drawings cite ISO 3302-1 tolerance classes. Send the class with your drawing and we confirm during DFM whether we can hold it. Tighter than ±0.1 mm is a design review, not a catalog option.
Process Capabilities
Compression molding. In-house, up to 250 tons.
Overmolding. In-house, silicone bonded to metal or plastic.
Extrusion. In-house. Tubing, cord, and profiles.
Die cutting. In-house. Thin gaskets, pads, and washers.
CNC mold making. In-house tooling for silicone.
LSR injection. Through our partner, not in-house.
Hybrid LSR on compression. In-house.
For the method detail, see our production methods, the compression molding guide, and extrusion services.
Tooling
Steel is the default mold material. Steel holds its dimensions across the full run, so one low-cavity tool runs your market test and, for small orders, your production.
- Tooling: 20 calendar days, an estimate.
- DFM review: within 24 hours.
- First samples after tooling: 1 to 2 days.
- Prototype route 1: 3D-printed mold, about 3 days, functional test only.
- Prototype route 2: low-cavity steel mold, about 200 pieces for a market test.
The tool is your property from the day it is cut. We store it free and ship it to any factory you name. There is no MOQ.
Testing and Compliance
Management systems: ISO 9001:2015, ISO 14001:2015, ISO 45001:2018.
We do not hold IATF 16949.
- Food contact: FDA 21 CFR 177.2600, LFGB, (EC) 1935/2004, NSF/ANSI 51.
- Biocompatibility (material): USP Class V and VI, ISO 10993.
- Restricted substances: RoHS, REACH/SVHC, EN 71-3, Proposition 65, BfR.
- Flammability: UL 94.
Hardness is tested per ASTM D2240. Tensile and elongation are tested per ISO 37 Type 2. Tear is tested per ASTM D624. Compression set is tested per ASTM D395 B. Density is tested per ISO 2781. Lab reports are available on request.
For the compliance detail, see ISO and FDA compliance and testing methods.
Questions Engineers Ask
What is your standard tolerance?
±0.2 mm standard, ±0.1 mm minimum. We machine molds to 0.03 mm. The thinnest silicone wall is 0.5 mm.
What durometer range do you run?
Shore A 10 to 80 for HTV and LSR. Shore A 30 to 80 for extrusion.
Do you run LSR in-house?
No. LSR runs through our partner. We handle quoting, DFM, QC, and the guarantee. Compression molding, overmolding, extrusion, die cutting, and CNC tooling run in-house.
What is your mold lead time?
20 calendar days for tooling. This is an estimate, not a guarantee. DFM review is within 24 hours.
Do you hold IATF 16949?
No. We hold ISO 9001:2015, ISO 14001:2015, and ISO 45001:2018.
What temperature can your silicone handle?
Default silicone runs -50 to +200 °C continuous, with about 230 °C short peak. Custom compounds can extend to about 300 °C, stated per grade.