Desktop
Resin Data
PE

Polietileno

PE·Polyethylenes·Semi-crystalline

Polyethylene (PE) is the #1 plastic in the world —110+ million tons per year, nearly 1 of every 3 kg of plastic produced on the planet— and under that generic name lives an entire family of variants with radically different properties depending on density, molecular weight, and catalyst. All share the same chemical base unit (CH₂-CH₂) but chain architecture —linear, branched, ultra-long— defines everything.

The five major families: LDPE (Low Density, branched), LLDPE (Linear Low Density, linear with co-monomer), MDPE (Medium Density, intermediate), HDPE (High Density, maximum crystallinity), and UHMWPE (Ultra-High Molecular Weight, molecular weight 3-7 million g/mol). When someone says "polyethylene" without qualification, they usually mean LLDPE (packaging films) or HDPE (bottles and pipes).

Reference brands: ExxonMobil Exceed S (latest-gen metallocene mLLDPE), Dow Elite (octene-based PE), SABIC Supeer, LyondellBasell. For UHMWPE: Celanese GUR, Mitsui Hi-Zex Million, Braskem UTEC. Polyethylene HDPE/MDPE represents 47% of the market, and LLDPE grows at 5.5% annually —the most dynamic segment. Are you running a specific PE? Share your experience and specialty in the comments.

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)1.21:1
L/D Ratio18 – 24
Compression Ratio2 – 3
Tonnage Factor3.86 – 5.41kN/cm²
Thermal Diffusivity0.1702mm²/s
Max Shear Rate40,0001/s
Shrinkage0.2 – 0.8%
Regrind50%
Heat Deflection (HDT) @ 1.82 MPa121°C
Glass Transition (Tg) @ 10°C/min-120°C
Vicat Softening @ 50N70°C

Drying

Drying Temperature85 – 91°C
Drying Time1 – 2h
Recommended Moisture0.02%
Recommended Dryer TypeDesiccant
Dew Point-40°C

Temperatures

Melt254 – 277°C
Nozzle191 – 302°C
Front229 – 302°C
Middle221 – 291°C
Rear210 – 282°C
Demolding82 – 99°C
Mold (Cooling)66 – 88°C
Feed Throat35 – 79°C

Processing

Back Pressure3.4 – 13.8bar
Screw Speed40 – 100RPM
Injection SpeedHigh
Barrel Occupancy20 – 85%
Injection Pressure700 – 1,400Pbar
Holding Pressure175 – 1,120Pbar
Cushion6.4 – 12.7mm

Mold

Runner Diameter4.57 – 9.14mm
Gate Diameter1.02 – 2.03mm
Gate Area0.81 – 3.24mm²
Wall Thickness0.76 – 5.08mm

Venting

Depth (Vent Depth)0.0102 – 0.0305mm
Land (Vent Land)0.508 – 1.02mm
Width (Vent / Clearance)3.05 – 10.2mm
Relief (Relief Channel)0.127 – 0.254mm

Frequently asked questions

Two main parameters: **density** (more density = more crystallinity, more rigidity, less transparency) and **molecular architecture** (linear vs branched chain, molecular weight). Ranges: **LDPE** 0.910-0.925 g/cm³ (highly branched, soft, transparent), **LLDPE** 0.915-0.925 (linear with controlled short branches), **MDPE** 0.926-0.940 (intermediate), **HDPE** 0.941-0.965 (linear, rigid, opaque), **UHMWPE** 0.930-0.935 (linear but ultra-long chains, unique properties).
**LDPE** (Low Density): made by high-pressure polymerization without specific catalyst, chains branch randomly ("tree" structure). Result: very clear, very flexible, easy to process, **but low mechanical strength**. **LLDPE** (Linear Low Density): made by low-pressure polymerization with Ziegler-Natta or metallocene catalysts, adding co-monomer (1-butene, 1-hexene, 1-octene) that creates controlled short branches. Result: same density as LDPE but **higher tensile, impact, and puncture resistance** —replaced LDPE in most packaging films.
**UHMWPE** (Ultra-High Molecular Weight Polyethylene) has chains with molecular weight of **3-7 million g/mol** —vs 50-200 thousand for conventional HDPE. This gives it unique properties: **highest wear resistance of any plastic**, maximum impact strength, **extremely low friction coefficient**, **biocompatible**. Flagship applications: **hip and knee implants** (85% of the world market uses UHMWPE as bearing surface, ~50 years of medical use), **bulletproof vests and armor** (Dyneema, Spectra fibers), **industrial bearings and bushings**, **port crane load supports**.
By **global volume**, **HDPE/MDPE** combined leads with 47% of the total market. By **individual applications**, dominants are: **HDPE** in rigid bottles (milk, detergent, non-carbonated soda), drums, gas and water pipes. **LLDPE** in packaging films (stretch wrap, supermarket bags, greenhouse films). **LDPE** in softer flexible films and snap-on caps. **PE-RT** (Raised Temperature, similar to MDPE with co-monomer) in modern residential hot water plumbing.
**mPE** (metallocene PE) is produced with **metallocene catalysts** —zirconium or titanium complexes with cyclopentadienyl ligands. Vs traditional Ziegler-Natta catalysts, metallocenes produce polymers with **narrower molecular weight distribution**, **more uniform co-monomer distribution**, and **fewer extractables**. Result: clearer films at lower thickness for same strength (downgauging), lower seal temperature, better organoleptic performance for food packaging. **ExxonMobil Exceed S** and **Dow Elite** are references.
Varies widely by grade: - **LDPE/LLDPE injection**: melt 180-240°C, mold 20-40°C - **MDPE**: melt 200-260°C, mold 20-50°C - **HDPE injection**: melt 220-280°C, mold 20-60°C - **UHMWPE**: **not processed by conventional injection** —its viscosity is so high it requires **ram extrusion** or **compression molding**. Some special grades (very-high molecular weight, not ultra) can be injected at 220-280°C with care.
**Yes, conventional grades are**: codes **#2 (HDPE)** and **#4 (LDPE/LLDPE)** are widely accepted in municipal systems. PE is one of the **most recyclable plastics in the world** —simple hydrocarbon chain, no halogens, no complex additives in commodity grades. **rPE** (recycled PE) in food-contact grades is FDA and EFSA approved with source-by-source limitations. **UHMWPE is not conventionally recycled** —too specialized, gets re-melted for non-critical components.
**PE** wins on: higher flexibility (especially at low temperature), stress-crack resistance, transparency for thin films, cost (LDPE/LLDPE). **PP** wins on: rigidity (higher modulus), service temperature (up to ~100°C vs 70°C for HDPE), fatigue resistance (PP "living hinge"), water vapor barrier. **Rule of thumb**: for films, sacks, soft packaging, cables → **PE**. For hinged caps, rigid heat-resistant containers, fibers → **PP**.
One of the highest variabilities of any plastic: - **LDPE/LLDPE**: 1.5-2.5% (anisotropic) - **MDPE**: 1.5-3.0% - **HDPE**: 1.5-3.0% (can reach 4% in thick parts) - **Molded UHMWPE**: 2-4% due to maximum crystallization PE's high shrinkage is a direct consequence of its **high crystallinity** —the material is ~50-90% crystalline, vs amorphous like PC or ABS at 0.4-0.7%. Mold design with oversizing is mandatory.
**PEX** (Cross-linked Polyethylene) is PE with **chemical bonds formed between chains** by three methods: **PEX-A** (peroxide during extrusion), **PEX-B** (silanes + water post-extrusion), **PEX-C** (gamma or electron beam radiation). The result: **three-dimensional network** that no longer melts —it's thermoset, not thermoplastic. Dominant application: **residential hot water plumbing** —the main replacement for copper and CPVC in USA and EU since 2010. 50+ year service life, fast install by crimping, no solvent welding.

Sources

Discussion (0)