Key Differences Between Liquid silicone rubber (LSR) and TPE
1. Material Composition and Curing Process
| Property | LSR (Liquid Silicone Rubber) | TPE (Thermoplastic Elastomer) |
|---|---|---|
| Chemical Structure | Thermoset (permanently cured) | Thermoplastic (re-meltable) |
| Curing Mechanism | Platinum or peroxide-cured (irreversible) | Cooled and re-meltable (reversible) |
| Base Material | Silicone polymer (inorganic backbone) | Rubber/plastic blend (organic polymer) |
Key Difference:
LSR undergoes permanent vulcanization, while TPE can be reprocessed multiple times like conventional plastics.
2. Temperature and Chemical Resistance
| Resistance Type | LSR | TPE |
|---|---|---|
| Heat Resistance | -50°C to 250°C (short-term 300°C possible) | -40°C to 120°C (some grades up to 150°C) |
| Flame Resistance | Naturally flame-retardant (V0 rated) | Requires additives for flame resistance |
| Chemical Resistance | Excellent (oils, acids, solvents) | Moderate (degrades with oils/UV exposure) |
Why It Matters:
LSR is preferred for high-temperature applications (e.g., kitchenware, automotive), while TPE is better for room-temperature flexible parts.
3. Mechanical Properties
| Property | LSR | TPE |
|---|---|---|
| Tensile Strength | 4-12 MPa | 5-50 MPa (varies by grade) |
| Elongation at Break | 200-1000% | 100-1300% |
| Compression Set | Excellent (minimal permanent deformation) | Poorer (may not fully recover) |
| Tear Strength | Low to moderate | Generally higher than LSR |
Functional Impact:
LSR maintains elasticity longer under compression (better for seals & gaskets).
TPE has higher tear resistance (good for durable grips).
4. Manufacturing and Processing
| Factor | LSR | TPE |
|---|---|---|
| Molding Process | Liquid injection molding (LIM) | Injection molding/extrusion |
| Cycle Time | Slower (requires curing) | Faster (no curing needed) |
| Tooling Cost | Higher (precision molds required) | Lower (standard plastic molds work) |
| Scrap Reusability | Non-recyclable (thermoset) | Recyclable (re-meltable) |
Production Consideration:
TPE is cheaper and faster for high-volume production, while LSR offers superior precision for medical/optical parts.
5. Biocompatibility and Safety
| Certification | LSR | TPE |
|---|---|---|
| Medical Grade | FDA, ISO 10993, USP Class VI compliant | Limited medical-grade options |
| Skin Contact | Hypoallergenic, odorless | May contain plasticizers (potential odors) |
| Sterilization | Autoclavable (steam/ETO/radiation) | Gamma/ETO only (limited heat resistance) |
Critical for:
Medical devices (LSR dominates implants & surgical tools).
Baby products (TPE requires careful formulation to avoid toxins).
6. Cost Comparison
| Cost Factor | LSR | TPE |
|---|---|---|
| Material Cost | $$$ (Higher raw material price) | $ (More affordable) |
| Tooling Investment | $$$ (High-precision molds) | $$ (Standard plastic tooling) |
| Per-Part Cost | Higher (for low volumes) | Lower (economical at scale) |
Budget Decision Guide:
Choose TPE for cost-sensitive, high-volume products.
Select LSR when performance justifies premium pricing.
7. Typical Applications
| Industry | LSR Applications | TPE Applications |
|---|---|---|
| Medical | Implants, respiratory masks, syringe seals | Medical tubing, catheter grips |
| Automotive | Engine gaskets, spark plug boots | Interior trim, door seals |
| Consumer Goods | Baby bottle nipples, bakeware | Phone cases, toothbrush grips |
| Electronics | Keyboard pads, waterproof seals | Cable sheathing, protective covers |