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Resin Data
HDPE

Polietileno de Alta Densidad

HDPE·Polyethylenes·Semi-crystalline

HDPE (High-Density Polyethylene) is the workhorse industrial plastic: rigid, tough, chemically resistant, food-grade certified, BPA-free, and the second-most-recycled polymer in the world (after PET). It is in milk jugs, detergent bottles, gas and water pipes, 55-gallon drums, beverage crates, outdoor toys, thick shopping bags, and thousands of applications where stiffness with toughness wins over everything else.

But it has two personalities depending on grade: injection grade (MFI 5–30) is different from blow molding grade (MFI 0.1–1) and from pipe grades (very low MFI). Picking the wrong MFI sends you straight to extreme warping, surface defects or ESC (environmental stress cracking) in the presence of detergents or solvents. Here we have compiled the reference ranges from the PDS, plus the questions that come up over and over on the shop floor: how to pick the right MFI, why jugs crack after months with soap, when to switch to PP, HDPE vs LDPE, what carbon black does and why it warps so much.

Share your experience in the comments — ranges vary by manufacturer and grade, and collective discussion is what gets us out of trouble on the floor.

The ranges shown in these data tables were compiled by the MVPS team from various parameter sheets and literature, integrating the lower and upper limits for each material type.

This information must be carefully reviewed when developing injection molding processes. Final ranges and processing tolerances are the responsibility of the engineer in charge.

These ranges are not recommended for developing specific process tolerances. MVPS always recommends requesting and consulting the supplier's data sheet.

General Properties

Chemical StructureSemi-crystalline
Specific Gravity (Density)1.05:1
L/D Ratio18 – 24:1
Compression Ratio2 – 4:1
Tonnage Factor3.09 – 6.18kN/cm²
Thermal Diffusivity0.1995mm²/s
Max Shear Rate40,0001/s
Shrinkage1.5 – 4%
Regrind50%
Heat Deflection (HDT) @ 1.82 MPa78°C
Glass Transition (Tg) @ 10°C/min-95°C
Vicat Softening @ 50N115°C

Drying

Drying Temperature49 – 60°C
Drying Time1 – 2h
Recommended Moisture0.5%
Recommended Dryer TypeAir
Dew Point-40°C

Temperatures

Melt179 – 282°C
Nozzle177 – 282°C
Front177 – 271°C
Middle171 – 260°C
Rear166 – 260°C
Demolding38 – 102°C
Mold (Cooling)21 – 91°C
Feed Throat10 – 49°C

Processing

Back Pressure3.4 – 13.8bar
Screw Speed40 – 70RPM
Injection SpeedHigh
Barrel Occupancy25 – 75%
Injection Pressure300 – 1,050Pbar
Holding Pressure75 – 840Pbar
Cushion6.4 – 12.7mm

Mold

Runner Diameter4.06 – 9.14mm
Gate Diameter1.02 – 2.03mm
Gate Area0.81 – 3.24mm²
Wall Thickness0.79 – 5mm

Venting

Depth (Vent Depth)0.0203 – 0.0508mm
Land (Vent Land)0.508 – 1.02mm
Width (Vent / Clearance)3.05 – 6.1mm
Relief (Relief Channel)0.254 – 0.381mm

Frequently asked questions

HDPE is a semi-crystalline polyolefin thermoplastic, synthesized by polymerizing ethylene with Ziegler-Natta or chromium catalysts. Result: linear chain with very few branches (unlike LDPE, which is highly branched), allowing dense crystalline packing (60–80% crystallinity). Typical density 0.94–0.97 g/cm³ (vs 0.91–0.94 for LDPE). Floats on water, but barely.
HDPE: linear chain, high crystallinity, rigid, chemically resistant, opaque. Ideal for bottles, pipes, drums, structural parts. LDPE: highly branched chain, low crystallinity, flexible, translucent. Ideal for films, bags, squeeze bottles, soft caps. LLDPE: linear but with controlled short branches — combines HDPE's toughness with LDPE's flexibility. Ideal for stretch film, premium bags, geomembranes. Rule of thumb: rigidity → HDPE, flexibility + clarity → LDPE, high-strength films → LLDPE.
Yes, food-grade approved by FDA and EFSA, and does NOT contain BPA or phthalates (synthesized only from ethylene). It is one of the safest plastics for food packaging — used in milk jugs, yogurt containers, reusable containers, modern baby bottles and kid toys. For specifically food-grade resin, ask the supplier for certification (additives may not be certified). Post-consumer recycled material for food contact requires a special FDA-approved process with a functional barrier.
MFI measures how much molten plastic flows in 10 minutes through a standard die under 2.16 kg at 190°C (g/10min). In HDPE it indirectly indicates molecular weight and thus viscosity. High MFI (15–30) = low molecular weight, low viscosity = injection grade (fills complex molds, fast cycle, but worse impact and worse ESCR). Low MFI (0.1–1) = high molecular weight, high viscosity = blow molding or pipe grade (better impact, better ESCR, but requires another process). Using blow grade for injection = short shots. Using injection grade for bottles = cracks when squeezed.
Environmental Stress Cracking (ESC). HDPE under mechanical stress (internal liquid pressure + tight closure) + in contact with surfactants (detergents, soaps, alcohols, vegetable oils) develops microcracks in stressed zones that progress. Solutions: (1) use bimodal HDPE with copolymer (butene or hexene) — 10–100× better ESCR, (2) reduce design stresses (no sharp corners, no very thin walls), (3) eliminate residual mold stresses (high mold temp, proper holding pressure), (4) standard test: ASTM D1693 with Igepal CO-630 at 50°C.
Very high shrinkage: 1.5–3%, the highest among commodities. And worse: it shrinks much more in the flow direction (~2–3%) than perpendicular (~1–1.5%), causing severe warping in large flat parts (boxes, lids). Solutions: (1) uniform wall with variations <15%, (2) hot mold (50–65°C) for complete symmetric crystallization, (3) generous cooling time — HDPE is slow to crystallize, short cycles = part with incomplete crystallinity that keeps shrinking in storage, (4) gate at part center, not at one end, for balanced radial flow, (5) consider HDPE with talc or nanosilica to reduce differential shrinkage.
Usually not. HDPE is very poorly hygroscopic (<0.01% ambient moisture), well below the critical threshold. That's why the PDS marks 'Air' as the dryer type or no drying at all. Exception: filled grades (glass fiber, talc, high carbon black concentration) may need light drying at 80°C for 1–2 h because the filler absorbs moisture. If you see silver streaks or bubbles, suspect the filler before the base HDPE, or a color masterbatch that was poorly stored.
The PDS marks 27–66°C. Hotter (50–65°C) = higher final crystallinity, better gloss, less residual stress, better ESCR, but significantly longer cycle. Cooler (30–45°C) = shorter cycle and high throughput, but parts with incomplete crystallinity that keep shrinking in storage and with higher warping risk. For bottles/jugs (where final rigidity and ESCR matter): 50–60°C. For commodity parts without critical requirements (crates, pallets): 30–45°C to optimize throughput.
HDPE wins on: low-temperature impact resistance (even at –40°C, while PP turns brittle), moisture barrier, ESCR with detergents (if you pick bimodal grade), weldability. PP wins on: service temperature (120°C vs 80°C for HDPE), stiffness, gloss, ability to make living hinges (HDPE doesn't survive repeated bending of a hinge). Rule of thumb: for jugs, drums, pipes, hard juice caps → HDPE. For hinged caps, microwavable containers, autoclavable parts → PP. For outdoor toys in cold climates → HDPE (doesn't shatter under impact in winter).
Without protection, no. Pure HDPE turns brittle and loses toughness under UV in 6–12 months outdoors. Standard solution: HDPE with carbon black (2–2.5% carbon black) — the most UV-resistant of all commodity plastics, lasting 20+ years in the sun (it's the material of gas pipes and geomembranes). If you need color: grades with HALS + UV stabilizers in white/colors, but shorter service life (5–10 years). For outdoor furniture and toys → UV-stabilized HDPE. For critical infrastructure (water/gas pipes) → PE100 HDPE with carbon black, certification EN 1555/12201.

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