🧩 COC – Cyclic Olefin Copolymer
(Transparent and weldable technical material with high rigidity, used in precision automotive components, optical covers, and housings)
🔹 What is COC
COC (Cyclic Olefin Copolymer) is an advanced olefinic copolymer obtained by combining ethylene with a cyclic olefin (e.g., norbornene).
The result is a transparent, rigid, lightweight, and dimensionally stable material that retains its olefinic character—meaning it can be thermally welded—but features superior hardness and optical clarity. COC is used in technical, optical, and medical applications, and in the automotive industry for sensor covers, lenses, diffusers, and indicators.
🔧 Composition
- Ethylene (PE) – flexible base.
- Cyclic Olefin (e.g., norbornene) – rigidity and clarity.
- Additives – UV stabilizers, anti-static agents, optical dyes.
- Density: ≈ 1.02 g/cm³.
- Melting Point: ≈ 170–180 °C.
- Refractive Index: 1.53–1.54.
🚗 Where COC is used in the automotive industry
| Component | Example parts | Observations |
| Auto Optics | Sensor covers, lenses, LED windows | Clarity and thermal stability |
| Technical Housings | Transparent and rigid parts | Excellent rigidity, low weight |
| Interior Elements | Decorative covers, inserts | Glossy appearance, fine surface |
| Sensors & Electronics | Optical diffusers | Electrical insulation and IR transparency |
🔧 Welding Temperature and Methods
| Method | Optimal Temperature | Observations |
| Hot Air | 250 – 270 °C | Precise, controlled welding |
| Heat Plate (Mirror) | 240 – 260 °C | Ideal for flat joints |
| Laser / Ultrasonic | — | Recommended for optical applications |
🔩 What to Weld COC With (Material Compatibility)
Since it is olefinic, COC welds only with materials from the same family (COC or COP) and partially with pure PE or PP.
✅ Compatible:
- COC ↔ COC – ideal combination.
- COC ↔ COP (Cyclic Olefin Polymer) – very good compatibility.
- COC ↔ PP / PE-HD – partial compatibility (superficial adhesion).
❌ Incompatible:
- ABS, ASA, PC, PA, PVC – polar materials, different melting points.
💡 ReplastMD Recommendation:
For repairs, use COC or PE-HD rods at a temperature of 255–265 °C with constant flow and low pressure. In aesthetic automotive applications, mirror (heat plate) welding is recommended for an invisible and glossy joint.
🏭 Manufacturers and Trade Names
- TOPAS Advanced Polymers: TOPAS® COC
- Zeon Chemicals: Zeonor® COC
- Mitsui Chemicals: Apel™ COC
- SABIC: Olefin Copolymer COC
🧠 How to Identify COC
- Engraved marking: >COC<, >TOPAS<, >ZEONOR<, >COP/COC<.
- Glossy, transparent, rigid surface.
- Yellow-blue flame, faint paraffin smell.
- Softens at ≈ 260 °C, without bubbling.
- Does not absorb water and does not deform under heat.
🛠️ COC Welding at ReplastMD:
At our service center in Chisinau (Ciocana sector), ReplastMD performs professional COC welding and bonding for:
- transparent covers and automotive sensors;
- optical housings and diffusers;
- restoration and sealing of rigid components;
- clear finish, glossy, without visible optical distortion.