🧩 PP+HT – High Temperature Resistant Polypropylene
(Thermally modified weldable plastic, used in automotive parts exposed to high heat)
🔹 What is PP+HT
PP+HT (High Temperature) is a polypropylene modified for thermal resistance, specifically developed for parts that operate at higher temperatures than standard PP.
Heat-stabilizing additives and special nucleating agents allow it to withstand up to 130–150 °C without deformation, while maintaining the characteristic low weight and weldability of PP.
🔧 Composition
- PP (Polypropylene) – semi-crystalline base
- HT (High Temperature Stabilizers) – heat-resistant additives and nucleating agents
- Additives – UV stabilizers, antioxidants, technical pigments
- Variants: PP-H+HT, PP-TD+HT, PP-GF+HT
🚗 Where PP+HT is used in the automotive industry
| Component | Example parts | Observations |
| Engine Compartment | Sensor covers, timing covers, air deflectors | Resistant to heat and vibrations |
| Technical Interior | Supports, covers, fasteners | Does not thermally deform |
| Exterior / Bodywork | Parts near exhaust or radiator | Stability at 130–150 °C |
| Other Applications | Industrial parts, mechanical supports | Durable, weldable, dimensionally stable |
🔧 Welding temperatures and methods
| Method | Optimal temperature | Observations |
| Hot air | 280 – 300 °C | Requires precise thermal control |
| Heat plate (mirror) | 270 – 290 °C | Recommended for clean joints |
| Manual extrusion | 260 – 280 °C | Good for technical repairs |
| Ultrasonic | — | Only for small industrial parts |
🔩 What to weld PP+HT with (Material compatibility)
The question “what to weld PP+HT with” is essential because thermal stabilizers can slightly modify the melting behavior.
However, PP+HT remains compatible with most polypropylene variants.
✅ Compatible:
- PP+HT ↔ PP+HT – ideal combination, stable joint
- PP+HT ↔ PP-H / PP-C / PP-TD – very good compatibility
- PP+HT ↔ PP-GF20 / PP-MD20 – partially compatible, slow melting
- PP+HT ↔ PP+FR – compatible, but requires precise temperature
❌ Incompatible:
- PE, ABS, ASA, PC, PA, PVC – different melting points and composition
💡 ReplastMD Recommendation:
Use PP-HT or standard PP welding rods and work between 285–295 °C. Ensure slow and uniform melting — if the surface becomes glossy without bubbles, the weld is correct.
🏭 Manufacturers and trade names
| Manufacturer | Brand / Series | Country / Region |
| LyondellBasell | Hostacom® HT | Germany / Netherlands |
| Borealis | Daplen® HT | Austria |
| SABIC | PP High Temp | Netherlands / Global |
| TotalEnergies | Lumicene® HT | France |
| Hyundai EP | Polytron® HT | South Korea |
| Ravago | Enyglos® HT | EU |
🧠 How to identify PP+HT
- Engraved marking: >PP-HT<
- Yellow-blue flame, smells like paraffin
- Slow melting at 290 °C, without bubbles
- Rigid surface, slightly glossy
- Does not soften under hot air below 260 °C
💡 ReplastMD Practical Test: If the part remains stable at 250 °C and becomes malleable only above 280 °C → PP-HT confirmed.