A procurement manager in Hamburg once rejected a full container of HDPE because the Certificate of Analysis showed a melting peak 7°C below the datasheet. The supplier insisted the material was “still HDPE.” Six weeks of lab testing later, the batch was confirmed as an off-spec blend with higher comonomer content. The lesson was expensive but simple: the HDPE melting point is not one fixed number.
If you specify, source, or process high-density polyethylene, you have probably seen datasheets quoting anywhere from 120°C to 140°C. That range is real, and it matters more than most buyers realize. In this guide, we explain what the HDPE melting point actually is, why it shifts between grades, how it differs from processing temperature, and what to verify on a COA before you commit to a batch.
Here is what you will learn:
- The precise melting range for HDPE, and how it compares with LDPE, LLDPE, PP, and UHMWPE
- Why pipe, blow-molding, and injection grades peak at different temperatures
- The critical difference between melting point, heat deflection, and processing temperature
- How to verify thermal consistency on a COA when sourcing from China
- Where to source certified HDPE with full documentation
What Is the Melting Point of HDPE?
HDPE typically melts at 120–135°C (248–275°F), with most commodity grades peaking near 130°C. High-density pipe grades can reach 135–140°C, and the equilibrium melting temperature for a perfectly ordered HDPE crystal is reported around 141–142°C. The exact value on any datasheet depends on density, crystallinity, molecular weight, comonomer content, and how the test was run.
High-density polyethylene is a semi-crystalline polymer. Its chains are nearly linear with very few branches, so they pack tightly into ordered crystallites. Those crystallites melt at a discrete temperature. The more crystalline the material, the higher the melting point. That is why HDPE melts higher than LDPE, whose branched chains cannot pack as tightly and form smaller, lower-melting crystallites.
Two HDPE grades with the same nominal density can report slightly different melting peaks. The manufacturer, catalyst system, nucleating agents, and thermal history all play a role. For engineers and buyers, the takeaway is: a melting point on a datasheet is a measured value, not a specification guarantee.
Need the melting peak for a specific branded grade before you commit? Browse our certified HDPE resin grades →
HDPE Melting Point vs. LDPE, LLDPE, PP, and UHMWPE
When you compare polyethylene families, the relationship between density and melting point becomes clear. The table below gives practical ranges for the thermoplastics you will most often see alongside HDPE in procurement discussions.
| Material | Density (g/cm³) | Melting Point (°C) | Melting Point (°F) | Why the Difference? |
|---|---|---|---|---|
| LDPE | 0.910–0.925 | 105–115 | 221–239 | Highly branched chains, low crystallinity |
| LLDPE | 0.915–0.925 | 110–125 | 230–257 | Short linear branches reduce packing |
| HDPE | 0.941–0.965 | 120–135 | 248–275 | Linear chains, high crystallinity |
| UHMWPE | 0.930–0.935 | 135–138 | 275–280 | Very high molecular weight, dense crystallites |
| PP | 0.900–0.910 | 160–175 | 320–347 | Different repeat unit, stronger chain interactions |
The pattern is consistent: melting point rises with density and crystallinity. HDPE sits above LDPE and LLDPE, while isotactic PP melts higher still. UHMWPE, despite a density below HDPE, peaks at the top of the range because its ultra-long chains form exceptionally dense crystallites.
This comparison matters for buyers because melting point is often used as a rough proxy for heat resistance. If a low-cost “HDPE” melts closer to 110°C, treat it as a red flag; it may be an off-spec or blended material. For a broader picture of how all engineering thermoplastics behave by temperature, see our engineering plastic temperature guide →.
Why HDPE Melting Point Varies by Grade
Not every HDPE grade behaves the same way at the crystalline level. The reported melting point moves for four main reasons.
Crystallinity
HDPE crystallinity typically falls between 70% and 90%. Higher crystallinity means more crystallites and stronger intermolecular packing, which raises the melting point. Pipe grades and blow-molding grades engineered for stiffness and chemical resistance sit at the high end of the range.
Molecular Weight
Higher molecular weight grades generally melt at slightly higher temperatures, because longer chains require more thermal energy to overcome crystalline bonding. Molecular weight also drives melt viscosity, which is why UHMWPE melts at 135–138°C yet processes very differently from commodity HDPE.
Branching and Comonomer Content
Even small amounts of comonomer introduce short-chain branches. These branches disrupt crystalline packing and lower the melting point. A pipe-grade HDPE with minimal branching melts higher than a film-grade HDPE formulated with more comonomer for flexibility.
Thermal History and DSC Conditions
The melting point on a datasheet is usually measured by Differential Scanning Calorimetry (DSC) to ASTM D3418 or ISO 11357. Heating rate, annealing history, and sample preparation can shift the reported peak by 2–5°C. That is why two datasheets for nominally similar grades can show different numbers, and why you should always verify against the manufacturer’s published value.
Melting Point Is Not Processing Temperature
This is the most common mistake in procurement and processing. The temperature at which HDPE melts is not the temperature at which you process it. Processing temperatures must be high enough to fully melt the resin and lower its viscosity for flow, but low enough to avoid thermal degradation.
| Process | Melt Temperature (°C) | Mold / Die Temperature (°C) | Why So Much Higher? |
|---|---|---|---|
| Injection molding | 180–280, commonly 220–260 | 20–95 | Needs low viscosity for cavity filling |
| Extrusion | 160–250 | Varies by die | Needs uniform melt for profile or pipe |
| Blow molding | 180–240 | Air-cooled parison | Needs melt strength to support parison |
| Rotational molding | 200–300 (mold temp) | Not applicable | Mold heats powder from outside |
Running HDPE at exactly its melting point would give a thick, barely molten mass. In practice, processors use a temperature buffer of 50–130°C above the melting peak. The buffer depends on the grade’s melt flow index (MFI), wall thickness, cycle time, and equipment.
MFI tells you where to set the melt temperature. INEOS’s injection-molding guidance is a useful rule of thumb: lower-MFR (higher-molecular-weight) grades need hotter melts, around 430°F ±10°F for a 2–6 MFR grade, while high-flow grades run closer to 400°F ±10°F at 25–45 MFR. Choose the melt temperature from the MFI, not from the melting point.
Mold temperature controls how quickly the molten HDPE crystallizes on cooling. Lower molds (20–50°C) give faster cycles but can increase warpage. Higher molds (50–95°C) improve surface finish and dimensional stability. For part quality, mold temperature is often more important than the exact melting peak.
HDPE Melting Point by Grade Category
Different HDPE grades are engineered for different processes, and their melting behavior reflects that. The table below shows typical ranges by application category.
| HDPE Grade Category | MFI Range (g/10 min) | Typical Melting Point (°C) | Key Thermal Consideration |
|---|---|---|---|
| Pipe grades (PE80 / PE100) | 0.2–0.6 | 130–135 | Long-term hydrostatic strength matters more than peak melting point |
| Blow-molding grades | 0.2–1.5 | 125–132 | Melt strength is critical; peak melting is secondary |
| Extrusion / film grades | 0.3–8 | 125–132 | Orientation and optical properties drive selection |
| Injection-molding grades | 4–50 | 125–133 | High MFI flows at lower melt temperatures |
| UV-stabilized / black grades | Varies | 125–135 | Additives do not significantly shift melting point |
Pipe Grades: PE80, PE100, PE4710
Pipe-grade HDPE is designed for decades of pressure service. The melting point is usually 130–135°C, but the more important specification is long-term hydrostatic strength certified to standards like ISO 4427 or ASTM D3035. A PE100 grade almost always melts at the high end of the HDPE range because of its high density and crystallinity.
Blow-Molding Grades
Blow-molded bottles and containers need enough melt strength to keep the parison from sagging before the mold closes. These grades have low MFI (0.2–1.5 g/10 min) and melting points around 125–132°C. For detergent or chemical containers, environmental stress cracking resistance (ESCR) usually matters more than the exact melting peak.
Injection-Molding Grades
Thin-wall caps, closures, and housewares use high-MFI grades (15–35+ g/10 min) that flow easily at 220–240°C. The melting point may be 125–133°C, but processors care more about MFI, mold shrinkage (1.5–3.0%), and cycle time than the crystalline melting peak.
Branded Grade Examples
To show how real datasheets vary, here are published melting peaks for named commercial grades:
- SABIC HDPE M864SE: ~135°C, injection-molding grade with a 32–38°C mold temperature recommendation
- Borealis CG9620: 131°C (DSC, ISO 11357-3), high-modulus grade
- LG Chem LUTENE-H BE0350: 134°C, blow-molding grade
- ERACLENE MR 80: 135°C, high-stiffness grade
Two things stand out. First, the spread across these four grades is only about 4°C, even though they serve very different processes. Second, those small differences come from density, crystallinity, and additive systems. A supplier quoting a melting point far outside 125–135°C for “HDPE” deserves scrutiny.
Melting Point vs. Heat Deflection and Service Temperature
Another common confusion is the difference between melting point and safe operating temperature. HDPE’s melting point is ~130°C, but its continuous service temperature is only around 82°C. Above that, the material softens and creeps under load long before it melts.
| Thermal Property | Typical HDPE Value | What It Means for Design |
|---|---|---|
| Melting point | 120–135°C | Temperature at which crystallites disappear |
| Heat deflection temperature (0.45 MPa) | 70–100°C | Stiffness drop under light load |
| Heat deflection temperature (1.82 MPa) | 40–80°C | Stiffness drop under higher load |
| Continuous service temperature | ~82°C | Safe long-term operating limit |
| Vicat softening point | 120–130°C | Temperature where a probe sinks under load |
| Thermal degradation onset | >250–300°C | Chain breakdown begins |
This distinction has real consequences. When a Melbourne appliance maker switched to a low-cost “HDPE” for a hot-fill part, they selected it on melting point alone: 132°C looked fine. The parts warped at 75°C in service. The grade they actually needed met a continuous-service rating near 82°C with adequate heat deflection, not just a high melting peak. Melting point tells you when a polymer stops being solid; it says almost nothing about how it will hold up under sustained heat and load.
One correction worth making while we are here: the widely repeated “PVC melting point 80°C” figure is not a melting point at all. PVC is amorphous, so it has no sharp crystalline melt. That ~80°C value is its glass transition temperature. HDPE, by contrast, is semi-crystalline and melts at 120–135°C. Our HDPE vs PVC guide → walks through these differences in material selection context.
How Melting Point Shows Up on a COA
When you buy branded prime HDPE, every shipment should arrive with a Certificate of Analysis (COA). The COA is your proof that the batch matches the manufacturer’s published specification. Here is what to check on the thermal side.
Required COA Fields
- Grade designation and manufacturer: confirms the resin is the exact grade you specified
- Melt flow index (MFI): indicates process viscosity; must match the datasheet range
- Density: confirms the high-density structure; should be 0.941–0.965 g/cm³
- Melting point or peak crystalline melting temperature: usually reported when tested
- Lot/batch number: enables traceability back to the manufacturer
Red Flags
- Melting point more than 5°C below the datasheet baseline
- Missing grade designation or generic descriptions like “HDPE granules”
- A supplier-generated COA instead of manufacturer-issued documentation
- Large lot-to-lot swings in MFI or density
- Price well below market for the stated grade
A procurement team in Dubai once caught a 9°C-low melting peak on a COA before unloading a container. The supplier had blended virgin and recycled material without disclosure. The melting-point line item was the first signal; a melt-index check confirmed it. Our HDPE melting point deep dive → covers additional testing details if you are setting up your own incoming inspection.
Sourcing Certified HDPE with Consistent Thermal Properties
Thermal consistency starts with the right supplier relationship. Yifuhui supplies branded prime HDPE from globally recognized manufacturers, with documentation for every batch.
What You Receive
- Manufacturer-issued Certificate of Analysis (COA)
- Material Safety Data Sheet (MSDS)
- Commercial invoice and packing list
- Compliance certificates where applicable (FDA, RoHS, REACH)
- Lot-level traceability for audit-ready supply chains
Logistics and Ordering
- Minimum order quantity: 25 kg for trial quantities
- Standard lead time: 7–14 days from Suzhou warehouse to major international ports
- Trade terms: EXW, FOB Shanghai, CIF
- Location: Suzhou, Jiangsu Province, adjacent to the Port of Shanghai
If you are qualifying a new HDPE grade, a 25 kg trial lets you verify melting point, MFI, and density against the datasheet before committing to a full container. Request a quote for certified HDPE resin with full COA documentation →
Frequently Asked Questions
What is the melting point of HDPE in Celsius?
HDPE typically melts at 120–135°C, with most grades around 130°C.
What is the melting point of HDPE in Fahrenheit?
That converts to approximately 248–275°F, or about 266°F for a typical grade.
Does HDPE melt in boiling water?
No. Boiling water at 100°C is below HDPE’s melting point. However, HDPE softens and deforms under sustained load above ~82°C, so it is not ideal for long-term boiling-water exposure under stress.
At what temperature does HDPE degrade?
Thermal degradation generally begins above 250–300°C in the absence of oxygen. In air, oxidative discoloration and embrittlement can start around 180–220°C, which is why processing temperatures stay inside controlled windows.
Why does HDPE melting point vary between datasheets?
Variations come from differences in crystallinity, molecular weight, comonomer content, nucleating agents, and DSC test conditions. Two similar grades from different manufacturers can easily differ by 2–5°C.
Is HDPE melting point higher than LDPE?
Yes. LDPE melts at 105–115°C, while HDPE melts at 120–135°C. The difference comes from HDPE’s more linear, more crystalline structure.
What is the difference between HDPE melting point and processing temperature?
Melting point is the temperature at which HDPE crystallites melt. Processing temperature is the much higher temperature used in extrusion, molding, or blow molding to make the resin flow, typically 180–280°C.
Conclusion
The HDPE melting point is a simple number with important nuance. Most grades melt between 120°C and 135°C, but the exact value depends on crystallinity, molecular weight, comonomer content, and test method. For processors, the melting point is only the starting point; the real operating window is the processing temperature, typically 50–130°C higher. For buyers, the melting point on a COA is a quick check on grade consistency and batch authenticity.
Before you place your next HDPE order, confirm three things: the grade matches your process, the COA values align with the manufacturer datasheet, and your supplier can deliver consistent, traceable batches. If you need certified HDPE with full documentation, Yifuhui supplies branded prime grades starting at 25 kg MOQ, shipped from Suzhou via the Port of Shanghai. To learn more about ABS Melting Temperature: Complete Processing and Grade Guide, please click to refer to our accompanying guide.
Ready to source HDPE you can verify? Request a quote with full COA documentation →
