🧩 PP – Polypropylene
(Lightweight and durable weldable plastic, widely used in the automotive industry)
🔹 What is PP
PP (Polypropylene) is a semi-crystalline thermoplastic with low weight, excellent chemical resistance, and low cost, being one of the most widely used automotive plastics.
It is well-known for its flexibility, impact resistance, and ease of welding, which is why it is used in most bumpers and body components.
🔧 Composition
- Propylene (C₃H₆) – main monomer
- Additives – UV stabilizers, antioxidants, colorants
- Common variants: PP-H (homopolymer), PP-C (copolymer), PP-TD (talc-filled), PP-GF (glass fiber reinforced)
🚗 Where PP is used in the automotive industry
| Component | Example parts | Observations |
| Body / exterior | Bumpers, spoilers, wheel arch liners, wheel covers | Lightweight, flexible, shock-resistant |
| Interior | Door panels, trims, dashboard elements | Matte surface, easy to mold |
| Auxiliary structures | Brackets, sensor covers, lower parts | Highly weldable, chemically stable |
| Tuning / DIY | Custom spoilers, extensions, ornaments | Ideal for hot air welding |
🔧 Welding temperatures and methods
| Method | Optimal temperature | Observations |
| Hot air | 260 – 280 °C | Most commonly used method in service shops |
| Heat plate (mirror) | 250 – 270 °C | Ensures uniform bonding |
| Manual extrusion | 240 – 260 °C | For long cracks and thick sections |
| Electrofusion | — | Rarely used, in technical applications |
🔩 What to weld PP with (Material compatibility)
Many ask what to weld PP plastic with — the answer is simple: only with PP or materials from the same polyolefin family (PP, PE).
Polypropylene has low surface energy, meaning it only adheres to similar materials.
✅ Compatible:
- PP ↔ PP – perfect bond, best result
- PP ↔ PP-C / PP-H – fully compatible
- PP ↔ PP-TD / PP-GF – partially compatible, for small areas only
- PP ↔ PE-HD / PE-LD – possible, but with reduced adhesion
❌ Incompatible:
- ABS, ASA, PC, PA, PVC – will not bond thermally, different melting points
💡 ReplastMD Recommendation:
Use original PP welding rods and work between 270–280 °C.
Clean the oxidized surface layer before welding for optimal adhesion.
🏭 Manufacturers and trade names
| Manufacturer | Brand / Series | Country / Region |
| LyondellBasell | Moplen®, Hostalen® PP | Germany / Netherlands |
| Borealis | Daplen® PP | Austria |
| SABIC | PP Compound Series | Netherlands / Global |
| TotalEnergies | Lumicene® PP | France |
| Hyundai EP | Polytron® PP | South Korea |
| Repsol | Isplen® PP | Spain |
🧠 How to identify PP
- Engraved marking: >PP<
- Yellow-blue flame, smells like paraffin (wax)
- Floats in water (density < 1 g/cm³)
- Matte surface, slightly waxy feel
- Softens uniformly at 270 °C
💡 ReplastMD Practical Test: If the plastic softens easily at 270 °C and smells like wax → it is PP.