🧩 NR – Natural Rubber
(Natural elastomeric material with remarkable elasticity and resilience, derived from natural latex. NR is prized for its resistance to fatigue, wear, and mechanical shock, used in dynamic automotive applications for vibration absorption.)
🔹 What is NR
NR (Natural Rubber) is a natural polymer of isoprene. At ReplastMD, we view it as the ultimate material for dynamic stress. Its ability to recover perfectly after deformation is almost unmatched by synthetic alternatives. However, being a thermoset material, it is permanently cross-linked during vulcanization. This means it cannot be re-melted or welded. It is the core of engine mounts and tires but remains sensitive to oils and UV exposure.
🔧 Composition & Properties
- Polymer Base: Natural cis-1,4-polyisoprene.
- Density: 0.92 – 0.97 g/cm³.
- Hardness (Shore A): 30 – 80.
- Operating Range: –50 °C to +80 °C.
- Chemical Resistance: Good for water; poor for oils/solvents.
- Weakness: Degrades quickly under ozone and UV without protective additives.
🚗 Where NR is used in the automotive industry
| Component | Example parts | Observations |
| Anti-vibration | Engine mounts, buffers, bushings | High elasticity, efficient damping |
| General Gaskets | Rings, simple seals | Water resistant, not for oil |
| Tires | Base layers and casings | High elasticity and adhesion |
| Suspension Parts | Sleeves, protectors, caps | Tough, but ozone sensitive |
🔧 Welding Temperature and Methods
| Method | Compatibility | Observations |
| Hot Air | ❌ Cannot be welded | Thermoset – burns and chars |
| Heat Plate (Mirror) | ❌ Impossible | Thermally degrades, does not flow |
| Extrusion | ❌ N/A | Cannot be reshaped after vulcanization |
| Chemical Bonding | ✅ Recommended | Rubber-based or neoprene adhesives |
🔩 Compatibility (Bonding)
- ✅ Compatible: NR, SBR, BR, IR, EPDM.
- ❌ Incompatible: PP, PE, PA, PC, PVC – no adhesion without chemical treatment.
💡 ReplastMD Recommendation: NR cannot be thermally welded. While simple tears can be fixed with rubber contact adhesives, for structural parts like bushings or engine mounts, total replacement is the only safe professional recommendation.
🧠 How to Identify NR
- Soft, elastic, matte texture.
- Color: Black (with carbon black) or beige (natural).
- ReplastMD practical test: Extremely elastic – stretches and returns completely. Burns with black smoke and a sweet rubbery scent.
- Common markings: >NR<, >NATURAL RUBBER<.