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PE injection molding is the process of heating and injecting molten polyethylene into a mold cavity to produce a finished part. This process is used for manufacturing everything from consumer products to industrial components.
Melting: PE pellets are heated to ~180–280°C depending on the type.
Injection: The molten PE is injected into a mold under pressure.
Cooling: PE cools and solidifies within the mold.
Ejection: The formed part is ejected once fully cooled.
Post-processing: Parts may be trimmed, printed, or assembled.
PE is used in a wide variety of industries:
Caps and closures, containers, toys, kitchenware
Food containers, bottles, flexible lids
Fuel tanks, fluid containers, cable insulation
Chemical tanks, bins, crates, tool housings
Irrigation components, sprayer housings, fertilizer tanks
| Property | LDPE | HDPE |
|---|---|---|
| Density | ~0.91 g/cm³ | ~0.94–0.97 g/cm³ |
| Melting Temp | ~105–115°C | ~120–130°C |
| Tensile Strength | Lower | Higher |
| Impact Resistance | Very High | High |
| Chemical Resistance | Excellent | Excellent |
| Flexibility | Very High | Moderate |
| Shrinkage | ~1.5–3.5% | ~1.5–3% |
Melt Temperature: 180–280°C (depending on PE grade)
Mold Temperature: 20–70°C (higher temp gives better surface finish)
Injection Pressure: Moderate (600–1,000 bar)
Drying: Not required – PE does not absorb moisture
Wall Thickness: 1.5–5 mm
Draft Angle: 1–2° for easy ejection
Ribs and Bosses: Use sparingly to avoid sink marks (PE is soft)
Rounded Corners: Prevent stress concentration and improve flow
Undercuts: Avoid unless side actions are available in the mold
Excellent Chemical Resistance: Performs well with acids, bases, alcohols
Impact Resistance: Very durable, especially in low temperatures
Low Cost: Raw material and processing are economical
Recyclable: Resin codes #2 (HDPE) and #4 (LDPE)
Food Safe: FDA-compliant grades available
Moisture Resistance: Hydrophobic and ideal for water-tight parts
Low Heat Resistance: Softens at relatively low temperatures
Difficult to Bond or Paint: Requires flame or corona treatment
High Shrinkage: Can make dimensional control challenging
Surface Finish: May appear waxy and less glossy than ABS or PC
Warping: Parts may distort if cooling isn’t uniform
| Property | PE | PP | ABS |
|---|---|---|---|
| Flexibility | High (LDPE) | Moderate | Low |
| Chemical Resistance | Excellent | Excellent | Moderate |
| Heat Resistance | Low | Moderate | Moderate |
| Stiffness | Low (LDPE) / High (HDPE) | Medium | High |
| Paintability | Poor | Poor | Good |
| Recyclability | Excellent | Excellent | Good |
| Shrinkage | High | Moderate–High | Low |
| Defect | Cause | Solution |
|---|---|---|
| Warping | Uneven cooling | Improve cooling system or part design |
| Sink Marks | Thick sections | Use ribs instead of solid walls |
| Short Shots | Inadequate flow | Increase temperature or pressure |
| Flash | Mold mismatch | Ensure proper mold alignment and clamping force |
| Burn Marks | Trapped air | Improve venting in mold design |
Choose PE when you need:
High toughness
Chemical or moisture resistance
Cost-effective production
Lightweight, durable parts
Food-grade or medical-safe plastics
It's not ideal for parts requiring high heat resistance, precise tolerances, or premium surface finishes.
For mass production of PE parts, expert mold design is critical due to its high shrinkage and warping potential. Manufacturers like SWY MOULD can assist with:
Optimal gate and runner design
Correct draft angles and venting
High-quality steel choices for wear resistance
Shine
Email: shine@swymould.com
Phone: +86 15757668880
