High Density Polyethylene (HDPE)
Take the branches away and the chains pack. That single architectural difference is worth 70% crystallinity, three times the stiffness of LDPE, and a pipe that carries pressurised water for fifty years.
Molecular Structure
What is High Density Polyethylene (HDPE)?
HDPE is polyethylene with the branching taken out. It is made at low pressure over a Ziegler-Natta, Phillips chromium or metallocene catalyst, in slurry loop, gas phase or solution processes, and the catalyst inserts ethylene in a controlled way that leaves the backbone essentially linear. With nothing obstructing them, the chains fold into crystals — 70 to 80% of the material is crystalline, against 45 to 55% for LDPE.
Everything else follows from that. Density rises to 0.941 to 0.965 g/cm³, stiffness roughly triples, the resin becomes opaque, and chemical and moisture resistance improve markedly. What is lost is flexibility, clarity and the melt strength that comes from long-chain branching.
The commercially interesting grades sit at the high molecular weight end, where the melt is too viscous to measure by ordinary melt flow index. Pipe and large blow moulding grades are made bimodally — a deliberate mixture of short chains that carry the comonomer for processability and long chains that carry the load — which is how a modern PE100 pipe resin achieves both extrudability and fifty-year pressure rating.
HDPE, LLDPE and LDPE all share CAS 9002-88-4, and the number tells a supplier nothing useful. Specify by density, melt index — stating whether it is MFI at 2.16 kg or HLMI at 21.6 kg — catalyst system, and the intended process. For pipe, quote the PE classification rather than a resin property.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
A linear polyethylene backbone with essentially no branching. Nothing obstructs the chains from folding into crystalline lamellae, and that close packing is the direct cause of HDPE's density, stiffness, opacity and chemical resistance.
Chain architecture — linear and unbranched, so chains pack closely
Structural Identity
- PolymerPolyethylene, high density
- Repeat unit(C₂H₄)ₙ — ethylene
- Repeat unit mass28.05 g/mol
- ArchitectureLinear, essentially unbranched
- Crystallinity70 – 80%
- Made byZiegler-Natta, Phillips Cr or metallocene
- ProcessesSlurry loop, gas phase, solution
- High-end gradesBimodal molecular weight distribution
- Defining propertyStiffness, ESCR and chemical resistance
- CAS Number9002-88-4 — generic to polyethylene
- Specified byDensity, MFI or HLMI, catalyst
Product Specifications
Chelora supplies High Density Polyethylene (HDPE) in standard and custom grades. Contact us for specification sheets tailored to your process.
| Polymer | High density polyethylene |
|---|---|
| CAS Number | 9002-88-4 (generic) |
| Repeat unit | (C₂H₄)ₙ |
| Density | 0.941 – 0.965 g/cm³ (ISO 1183) |
| Melt flow index | 0.02 – 20 g/10 min at 190 °C / 2.16 kg (ISO 1133) |
| High load melt index | 2 – 45 g/10 min at 190 °C / 21.6 kg — for pipe and BM grades |
| Melting range (DSC) | 125 – 135 °C |
| Vicat softening point | 120 – 129 °C |
| Tensile strength at yield | 22 – 31 MPa |
| Flexural modulus | 900 – 1550 MPa |
| ESCR (F₅₀, Bell test) | Grade dependent — state the test condition |
| Pipe classification | PE80 or PE100 to ISO 4427 / ISO 12162 |
| Carbon black (pipe grades) | 2.0 – 2.5 wt%, dispersion to ISO 18553 |
| Volatiles (max) | ≤ 0.10 wt% |
| Ash (max) | ≤ 0.02 wt% |
| Additive package | Antioxidant; UV, slip and antistatic to order |
| Food contact | FDA 21 CFR and EU 10/2011 declarations available |
| Packaging | 25 kg bags, 500 – 1250 kg jumbo bags, bulk |
| Transport classification | Not regulated as dangerous goods |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of High Density Polyethylene (HDPE).
Pressure Pipe
PE80 and PE100 pipe for potable water and gas distribution. Bimodal resins combine extrusion processability with a fifty-year pressure rating and excellent slow crack growth resistance.
Blow Moulded Containers
Milk and juice bottles, household chemical packaging, jerrycans, drums and IBC inner bottles, where stiffness, barrier and stress crack resistance all matter at once.
Injection Moulding
Crates, bins, pallets, caps and closures, pails and thin-wall containers, using higher melt index grades where flow rather than toughness governs.
HMW Film
High molecular weight HDPE film for carrier bags, refuse sacks and merchandise bags — very high strength at very thin gauge, with the characteristic crisp handle.
Rotomoulding & Tanks
Water tanks, chemical tanks, road furniture and marine buoys, using hexene grades with controlled particle size and long-term thermal stability.
Geomembrane & Liner
Landfill caps and basal liners, pond and canal lining, and mining leach pads, where chemical resistance and multi-decade durability are the specification.
Why source High Density Polyethylene (HDPE) through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market or off-spec prime passed as prime.
Grade Flexibility
Pipe, blow moulding, injection, film and rotomoulding grades supplied. We match on density, melt index at the correct load, catalyst system and whether the resin is unimodal or bimodal.
Full Documentation
Technical data sheet, CoA against the grade specification, SDS, REACH compliance, potable water and food-contact approvals, and pipe classification certification where applicable.
Logistics Support
Experienced in polymer resin logistics — 25 kg bags, jumbo bags, containerised and bulk silo delivery, with pellet-loss controls in line with Operation Clean Sweep, for Indian and international delivery.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Store pellets dry, indoors and out of direct sunlight, with bags off the ground and away from external walls. Condensation on cold pellets causes voids and surface defects in mouldings and film.
- Rotate stock and protect from UV. Sunlight consumes the antioxidant package before the resin ever reaches the extruder, and the loss is not visible on inspection.
- Contain pellets rigorously. Spilled pellets travel through drains into watercourses and are a recognised marine litter source — catch trays, drain screens and Operation Clean Sweep procedures should be standard at every transfer point.
- Handle carbon-black pipe grades on dedicated equipment where possible. Black pellets contaminating a natural or coloured production run are visible in the finished part and unrecoverable.
- Ground and bond pneumatic conveying, and control fines. Pellet fines cause gels and die build-up as well as presenting a dust explosion risk in silos and dust collectors.
- Use low-velocity conveying and correctly radiused bends. High-velocity transfer produces angel hair and streamers that block screens and hoppers.
- Extract at the die and hopper. Polyethylene degrading above about 300 °C releases aldehydes including acrolein, plus organic acids, all respiratory irritants.
- Treat molten polymer as a serious thermal burn hazard — it adheres to skin and retains heat, so die changes, screen pack changes and purging need forearm and face protection.
- Segregate grades strictly. Pipe, food-contact and general grades should not share silos or conveying lines, and traceability matters for pressure pipe in particular.
Hazard Summary
Classification: HDPE in pellet form is not classified as hazardous under CLP. It is chemically inert, non-toxic and approved for potable water and food contact. The hazards are physical and process-related.
Thermal burns: molten polyethylene at 180–300 °C adheres to skin and continues transferring heat after contact. Purging, screen changes and die work are where these injuries occur, and protection must cover forearms and face rather than hands alone.
Processing fume: polyethylene degrading above roughly 300 °C releases aldehydes including acrolein, organic acids and hydrocarbon fragments, all respiratory irritants. High molecular weight grades run at high shear and can develop local hot spots well above the set temperature.
Dust and fines: pellet fines are combustible and can form explosible clouds in silos, conveying systems and dust collectors. Grounding, bonding and accumulation control apply as for any organic solid.
Pellet loss to the environment: polyethylene pellets persist in the marine environment and are an identified microplastic source. Containment, drain screening and spill recovery are the expected standard and are increasingly audited.
Slip hazard: loose pellets on hard flooring cause falls and remain a frequent source of lost-time injury in resin handling areas.
Fire: polyethylene burns readily once ignited with high heat release, dense black smoke and carbon monoxide. Bulk pellet and finished-goods storage fires are difficult to extinguish and warrant specific design consideration.
PPE minimum: safety glasses and gloves for pellet handling; heat-resistant gloves, arm protection and face shield for work at the die or on molten material.
Consult the full SDS and the grade technical data sheet for processing temperature limits, and confirm potable water or food-contact status for your specific application before use.
Frequently Asked Questions
Technical and commercial questions about High Density Polyethylene (HDPE) sourcing and specifications.
What is HDPE used for?
Pressure pipe for water and gas distribution is the flagship application, followed by blow moulded containers — milk bottles, jerrycans, drums and IBC bottles. Injection moulding takes crates, bins, pallets, caps and pails. High molecular weight HDPE film makes carrier bags and refuse sacks. Beyond those, HDPE goes into rotomoulded water and chemical tanks, and into geomembranes for landfill and mining containment.
How does HDPE differ from LDPE and LLDPE?
By branching, and therefore by crystallinity. HDPE is essentially linear, so its chains pack into crystals — 70 to 80% crystalline, density above 0.941, stiff, opaque and chemically resistant. LLDPE is linear but carries short branches from an alpha-olefin comonomer, giving 35 to 45% crystallinity, lower density and much higher tear and puncture strength. LDPE has long branches from high-pressure free radical polymerisation, is the least crystalline and least stiff of the three, and is the only one with real melt strength. Same repeat unit, same CAS, three different materials.
What is PE100, and what does bimodal mean?
PE100 is a pipe classification, not a resin property. It means the material has a minimum required strength of 10 MPa when extrapolated to fifty years at 20 °C under ISO 12162, which allows thinner walls or higher pressure than PE80 at 8 MPa. Achieving it requires a bimodal resin: the polymer is made in two reactors in series, producing a deliberate blend of a low molecular weight fraction with little comonomer, which gives processability, and a high molecular weight fraction carrying most of the comonomer, which provides tie molecules between crystals and delivers slow crack growth resistance. A unimodal resin cannot reach both targets at once, which is why bimodal technology defined the modern pipe market.
Why is HLMI used instead of MFI for pipe grades?
Because the melt is too viscous for the standard test to give a usable reading. Ordinary melt flow index is measured at 190 °C under a 2.16 kg load, and a high molecular weight pipe resin will extrude so little material in ten minutes that the result is imprecise and irreproducible. Raising the load to 21.6 kg — the high load melt index, sometimes written MFI 21.6 or HLMI — puts the flow into a measurable range. The practical consequence is that a melt index figure means nothing without its load condition attached, and quoting 0.3 without saying which test has caused more than one ordering error.
What is ESCR and why does it matter?
Environmental stress crack resistance measures how long the material survives under sustained stress while in contact with a surface-active agent such as detergent. It matters because polyethylene rarely fails by breaking under load in a single event; it fails slowly, by cracks growing at stress concentrations over months or years, and detergents and oils accelerate that enormously. Any part that is stressed in service and in contact with a chemical — a bottle holding household cleaner, a pipe under internal pressure, a moulded crate that flexes — needs an ESCR specification alongside stiffness. Higher molecular weight and better comonomer distribution both improve it, which is exactly what bimodal resins are engineered for.
What documentation does Chelora provide?
Every shipment includes the grade technical data sheet, a Certificate of Analysis against the grade specification covering density, melt index at the stated load, volatiles and ash; a Safety Data Sheet to GHS and REACH format; REACH polymer compliance confirmation; food-contact declarations under FDA 21 CFR 177.1520 and EU Regulation 10/2011 where applicable; potable water approvals and pipe classification certification for PE80 and PE100 grades; an origin certificate; and destination-market certificates where required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about High Density Polyethylene (HDPE) grade, volume, logistics, documentation, and lead times. We respond within one business day.
