Choosing the right silicone rubber sheet requires careful consideration of your specific application's needs. Here's a step-by-step guide to the key factors:
1. **Identify Primary Application & Key Requirements**
- **Temperature Range:**
* Standard silicone: -50°C to +200°C (-60°F to +392°F).
* High-temp silicone: Up to +250°C or +300°C (e.g., for oven gaskets, automotive).
- **Chemical/Environmental Exposure:** Ozone, UV, acids, bases, solvents, steam, oils, or weathering.
- **Electrical Properties:** Need insulation? Specify voltage requirements.
- **Mechanical Stress:** Compression (gaskets), tension, abrasion, or tear resistance.
- **Regulatory Compliance:** FDA (food contact), USP Class VI (medical), NSF, UL, ROHS, REACH, or potable water approvals.
- **Movement/Flexibility:** Dynamic seals vs. static pads.
2. **Select Hardness (Durometer - Shore A Scale)**
* **Soft (20A-40A):** Excellent sealing/conformability (gaskets, cushioning).
* **Medium (50A-60A):** Balanced flexibility/strength (general purpose).
* **Firm (70A-80A+):** High abrasion resistance, structural support (wear pads, wipers).
3. **Determine Thickness & Tolerance**
* **Common Thicknesses:** 0.5mm (0.020") to 6mm (0.250") or thicker.
* **Criticality:** Precision gasketing needs tight tolerances (±0.1mm); cushioning allows looser specs.
* **Function:** Thinner = more flexible; thicker = more compression force/sealing.
4. **Choose Material Grade**
* **General Purpose:** Cost-effective for non-critical uses.
* **Food Grade (FDA/USP):** Kitchens, food processing, dairy.
* **Medical Grade (USP Class VI/ISO 10993):** Implants, medical devices, pharmaceuticals.
* **High-Temperature:** Extreme heat applications (red/special formulations).
* **Conductive/Faraday Cage:** Carbon-filled for EMI shielding.
* **Flame Retardant (UL 94):** Electronics, transportation.
5. **Consider Color & Appearance**
* **Standard:** Translucent, white, black, red (high-temp).
* **Custom Colors:** For coding, aesthetics, or UV resistance (pigments).
* **Surface Finish:** Smooth (molded), textured (calendered), or fabric-reinforced.
6. **Evaluate Physical Properties**
* **Tensile Strength:** Resistance to pulling (≥7 MPa typical).
* **Elongation:** Stretch before breaking (≥350% typical).
* **Compression Set:** Ability to recover after compression (lower % = better).
* **Tear Strength:** Resistance to tearing (≥15 kN/m typical).
7. **Surface Properties & Adhesion**
* **Self-Adhesive Backing:** Needed? (PSA options available).
* **Bondability:** Will you glue it? Ensure compatibility with adhesives.
8. **Supplier & Quality**
* **Certifications:** Verify material certs (RoHS, REACH, FDA, etc.).
* **Consistency:** Reputable suppliers ensure batch-to-batch uniformity.
* **Samples:** **Always request samples** for real-world testing.
* **Cutting Services:** Need custom shapes? Check die-cutting/waterjet options.
Key Selection Checklist:
| **Factor** | **Options/Considerations** |
|----------------------|--------------------------------------------------------|
| **Temperature** | Standard (-50°C to 200°C) vs. High-Temp (up to 300°C) |
| **Environment** | UV/Ozone, chemicals, steam, oils, weather |
| **Hardness (Shore A)**| Soft (20A-40A), Medium (50A-60A), Firm (70A-80A+) |
| **Thickness** | 0.5mm to 6mm+; check tolerance (±0.1mm critical) |
| **Grade** | General, Food, Medical, Flame Retardant, Conductive |
| **Certifications** | FDA, USP Class VI, UL, NSF, ROHS, REACH |
| **Color/Finish** | Translucent, white, black, red; smooth/textured |
| **Key Properties** | Compression set, tear strength, elongation |
**Pro Tips:**
- **Test Extensively:** Simulate real conditions (temp, pressure, chemicals) with samples.
- **Consult Suppliers:** Reputable manufacturers (e.g., Rogers Corp, Stockwell Elastomerics, local suppliers) can recommend grades.
- **Avoid Substitutes:** Don’t use PVC/Viton/Nitrile unless silicone’s properties are essential.
