🧩 PE-MD – Medium-Density Polyethylene
(Weldable plastic balanced between flexibility and rigidity, used in automotive tanks, protections, and technical parts)
🔹 What is PE-MD
PE-MD (Medium-Density Polyethylene) is a medium-density polyethylene, positioned between PE-LD (low density) and PE-HD (high density). It has a partially linear molecular structure, which provides an excellent balance between elasticity, hardness, and stress-crack resistance. It is a versatile material used in tanks, guards, and protectors due to its high mechanical strength and ability to be perfectly welded through thermal methods.
🔧 Composition
- Ethylene (CH2) – polymerized under controlled pressure
- Additives – antioxidants, UV stabilizers, anti-static agents
- Density: 0.93–0.94 g/cm³
- Melting point: ≈ 125–130 °C
🚗 Where PE-MD is used in the automotive industry
| Component | Example parts | Observations |
| Exterior | Lower protections, mudguards, housings | Good resistance to impact and abrasion |
| Engine Compartment | Tanks, covers, flexible pipes | Superior thermal stability |
| Technical Interior | Panels, deformable covers | Moderate elasticity, clean finish |
| Aftermarket | Auxiliary tanks, tool cases | Weldable, lightweight, and water-resistant |
🔧 Welding temperatures and methods
| Method | Optimal temperature | Observations |
| Hot air | 250 – 270 °C | Homogeneous melting, no bubbles |
| Heat plate (mirror) | 240 – 260 °C | Clean, watertight joint |
| Manual extrusion | 230 – 250 °C | Ideal for long cracks and corners |
| Electrofusion | — | Recommended for large pipes and tanks |
🔩 What to weld PE-MD with (Material compatibility)
PE-MD has excellent compatibility with other types of polyethylene, especially PE-HD and PE-LLD.
✅ Compatible:
- PE-MD ↔ PE-MD – ideal combination
- PE-MD ↔ PE-HD / PE-LD / PE-LLD – very good compatibility
- PE-MD ↔ Recycled PE / UV modified PE – compatible for minor repairs
❌ Incompatible:
- PP, ABS, ASA, PC, PA, PVC – will not bond, different melting point
💡 ReplastMD Recommendation: Use PE-MD or PE-HD welding rods at a temperature of 260–270 °C. Clean the area with isopropyl alcohol, remove the oxidized layer, and apply constant pressure during welding for a homogeneous joint.
🏭 Manufacturers and trade names
- LyondellBasell: Lupolen® MD
- Borealis: Borstar® MD
- SABIC: MDPE Compound
- TotalEnergies: Lumicene® MD
🧠 How to identify PE-MD
- Engraved marking: >PE-MD<, >MDPE<, >PE Medium Density<
- Semi-glossy surface, soft but firm to the touch
- Yellow-blue flame, paraffin smell
- Floats completely in water (density < 1 g/cm³)
- Softens uniformly at 260 °C, without smoke or bubbles
🛠️ PE-MD Welding at ReplastMD: At our service center in Chisinau (Ciocana sector), ReplastMD performs professional PE-MD welding for:
- tanks, protectors, and PE-MD / PE-HD covers
- crack, broken corner, and deformation repairs
- watertight joints and structural reinforcements
- uniform matte finish, ready for immediate use