PE-HD — High-Density Polyethylene
High-Density Polyethylene
PE-HD (high-density polyethylene) is a lightweight semi-crystalline thermoplastic offering excellent chemical resistance and a very low coefficient of friction. Widely used in injection molding for caps, jerrycans, sliding parts and containers.
- Mold temperature: 20-60°C
- Melt temperature: 200-280°C
- Shrinkage: 1.5-3.0%
- Density: 0.94-0.97
- Manufacturer grades: Hostalen GC 7260 (LyondellBasell), Marlex HHM 5502BN (Chevron Phillips)
Processing
PE-HD is not hygroscopic: no pre-drying is required, which simplifies processing. Run the melt between 200 and 280 °C with a mold regulated between 20 and 60 °C; its high shrinkage (1.5 to 3.0 %) calls for generous holding and uniform cooling to control dimensional instability and warpage.
Advantages
- No drying required (non-hygroscopic): simplified processing
- Excellent chemical resistance (acids, bases, solvents, water)
- Low coefficient of friction: sliding parts
- Low density and good impact resistance at low temperature
Limitations
- High shrinkage (1.5 to 3.0 %) prone to warpage and dimensional instability
- Low rigidity and limited thermal resistance
- Susceptible to environmental stress cracking (ESC) depending on medium
- Low surface adhesion: bonding and painting difficult without surface treatment
Common injection molding defects
- Sink marks — High semi-crystalline shrinkage: increase holding pressure and time on thick sections
- Warpage — Differential shrinkage: homogenize mold cooling and balance the fill
- Dimensional instability — High and slow shrinkage: extend holding and stabilize cycle time
Typical applications
Caps, containers, toys, piping