Views: 0 Author: Site Editor Publish Time: 2025-08-11 Origin: Site
| Property | Value/Range | Significance |
|---|---|---|
| Density | 0.941–0.965 g/cm³ | Higher than LDPE, providing rigidity |
| Melting Point | 120–140°C | Lower than PP, easier to process |
| Tensile Strength | 20–37 MPa | Good for load-bearing applications |
| Impact Resistance | High | Excellent for durable products |
| Chemical Resistance | Resists acids, alkalis, solvents | Ideal for chemical containers |
| UV Resistance | Moderate (requires additives) | Limited outdoor use without stabilization |
Drying: Not usually required (hygroscopicity <0.01%).
Regrind Usage: Up to 30% regrind possible (ensure cleanliness).
| Parameter | Setting | Notes |
|---|---|---|
| Melt Temperature | 180–260°C | Avoid exceeding 280°C (degradation risk) |
| Mold Temperature | 20–60°C | Cooler molds reduce cycle time |
| Injection Pressure | 70–120 MPa | High pressure for thick-walled parts |
| Injection Speed | Medium-Fast | Prevents weld lines in large parts |
| Cooling Time | 15–60 sec | Depends on wall thickness |
Shrinkage: 1.5–3.0% (compensate in mold design).
Draft Angles: ≥1° to facilitate ejection.
Gate Design:
Sprue Gate: For thick parts.
Edge Gate: For uniform filling.
Venting: Essential (HDPE releases volatiles).
| Industry | Typical Products |
|---|---|
| Packaging | Bottle caps, crates, thin-walled containers |
| Consumer Goods | Toys, housewares, cutting boards |
| Industrial | Pallets, chemical tanks, pipes |
| Automotive | Fuel tanks, interior trim |
| Property | HDPE | LDPE | PP | PVC |
|---|---|---|---|---|
| Density | High | Low | Medium | High |
| Rigidity | High | Low | High | Very High |
| Chemical Resistance | Excellent | Good | Excellent | Poor (to oils) |
| Cost | Low | Low | Medium | Medium |
Advantages of HDPE:
Low cost, recyclable (#2 plastic).
Excellent impact resistance (even at low temps).
FDA-approved grades for food contact.
Limitations:
Poor UV resistance (requires additives).
Lower heat resistance vs. PP.
| Problem | Cause | Solution |
|---|---|---|
| Warping | Uneven cooling | Increase mold temp, optimize cooling channels |
| Sink Marks | Insufficient packing | Increase holding pressure/time |
| Brittleness | Over-drying or degradation | Reduce melt temp, check regrind quality |
| Flash | Excessive injection pressure | Lower pressure, check clamp force |
Recyclability: HDPE is 100% recyclable (widely accepted as #2 plastic).
Bio-based HDPE: Emerging (e.g., sugarcane-derived).
Regrind Tip: Avoid >30% regrind to maintain mechanical properties.
HDPE is a versatile, economical material for injection molding, offering durability, chemical resistance, and ease of processing. Key to success:
Optimize mold design (account for shrinkage, venting).
Control melt temp (avoid degradation).
Leverage recyclability for sustainable production.
