Table of Contents
- What kind of plastic is HDPE?
- Notable properties of HDPE plastic
- What is the melting point of a plastic?
- Melting temperature of HDPE
- Comparison with other plastics
- Is HDPE plastic safe, is it toxic?
- What is HDPE 2 plastic? Why is it called plastic number 2?
- Can HDPE plastic be recycled?
- Frequently asked questions
- Contact ICD Vietnam for plastic pallet advice
- References
Reviewed and updated by ICD - Week 43/2026
HDPE melts between about 129 and 135 °C depending on crystallinity and grade; this is the melting peak measured by DSC under ASTM D3418, not a service temperature and not a processing temperature. In practice HDPE is processed at 190 to 240 °C (injection molding) or 150 to 210 °C (blow molding), well above the melting point so the plastic flows evenly.
This guide explains what the melting point of HDPE is, why it is a range and not a single number, how to compare it properly with other plastics (many have no melting point), and background on HDPE such as the number 2 symbol and recycling. For the service temperature limits of the product, see what temperature HDPE plastic can withstand.
What kind of plastic is HDPE?
HDPE (High-Density Polyethylene) is high-density polyethylene, polymerized from ethylene at low pressure using Ziegler-Natta, Phillips or metallocene catalysts. Its density is 0.93 to 0.97 g/cm3, with high stiffness and toughness. For an overview, see what HDPE plastic is.
Notable properties of HDPE plastic
HDPE’s strengths are mechanical strength, toughness and light weight, together with water resistance, recyclability and good electrical insulation. Chemically, HDPE resists acids and dilute bases, salts and alcohols well, but aromatic and halogenated hydrocarbons only poorly (BPF), and strong oxidizing acids attack polyethylene.
What is the melting point of a plastic?
The melting point is the temperature at which the crystalline regions of the plastic melt, turning the material from solid into a viscous liquid. The concept applies only to semi-crystalline plastics such as HDPE, PP or PET. Amorphous plastics such as rigid PVC, PS and ABS have no melting point; they have only a glass transition temperature (Tg) and soften continuously as they heat up. Understanding this avoids mistakes when comparing temperature tables between plastics.
Melting temperature of HDPE
ExxonMobil publishes the melting peak of HDPE grades in the range of 129 to 135 °C under ASTM D3418, and the datasheet for each grade usually states around 130 to 132 °C. The melting range depends on crystallinity and molecular weight: the more crystalline the plastic, the higher the melting peak and the stiffer it is.
Note that melting temperature is not processing temperature. To make the plastic flow evenly and fill the mold, processing machines are set above the melting point: 190 to 240 °C for injection molding (IRPC) and 150 to 210 °C for blow molding (ExxonMobil). Overheating, or leaving the plastic sitting in the heating barrel for long, causes burning, discoloration and degradation. For the flow of a specific grade, see the HDPE melt flow index guide.
Comparison with other plastics
The table below compares each plastic by its true nature: semi-crystalline types have a melting point (Tm), amorphous types have only a glass transition temperature (Tg).
| Plastic type | Melting Tm (°C) | Glass transition Tg (°C) | Notes |
|---|---|---|---|
| HDPE | 129 to 135 | about -110 | Semi-crystalline; Tm per ExxonMobil ASTM D3418 |
| LDPE | 105 to 120 | about -110 | Semi-crystalline; soft, used for film |
| PP | about 160 to 175 | about -20 to -5 | Semi-crystalline; more heat-resistant than HDPE |
| PET | about 252 to 253 | about 75 | Semi-crystalline; water bottles |
| Rigid PVC | none | about 80 | Amorphous; softens gradually when heated |
| PS | none | about 100 to 104 | Amorphous |
| ABS | none | about 104 to 105 | Amorphous; equipment housings |
Figures such as “PVC 100 to 260 °C, PS 100 to 120 °C, ABS 105 °C” are sometimes quoted as melting temperatures, but they are processing temperatures or the Tg of plastics that have no true melting point. The correct reading: HDPE melts at a mid-range level among the semi-crystalline plastics, lower than PP and PET, higher than LDPE.
Is HDPE plastic safe, is it toxic?
HDPE contains no bisphenol A (BPA), because BPA is a raw material of polycarbonate and epoxy resin, not of polyethylene. In the US, polyethylene for food use is regulated under 21 CFR 177.1520; in Vietnam it is QCVN 12-1:2011/BYT. A cautious recommendation: do not hold hot food in HDPE packaging when the manufacturer does not state heat resistance, because heat can cause migration.
What is HDPE 2 plastic? Why is it called plastic number 2?
The number 2 is a code in the resin identification system used for sorting during collection and recycling, helping consumers and recyclers recognize the plastic type and handle it correctly. The common codes are 1 (PET), 2 (HDPE), 3 (PVC), 4 (LDPE), 5 (PP), 6 (PS) and 7 (other plastics). The code is only for recycling sorting, not a food-safety certification.
Can HDPE plastic be recycled?
Yes. The process covers collection and sorting, washing, grinding, melt extrusion and pelletizing, after which the pellets go into plastic pipe, trash bins and household goods. According to the EPA, natural HDPE bottles reached a recycling rate of 29.3% in the US in 2018. In recycling, the plastic is melted again at a temperature above the melting point, and reprocessing changes the properties of the plastic.
Frequently asked questions
What is the melting temperature of HDPE plastic?
A melting peak of 129 to 135 °C under ASTM D3418 (ExxonMobil); individual grade datasheets usually state 130 to 132 °C; the specific figure depends on crystallinity and molecular weight.
What is the processing temperature of HDPE?
Injection molding 190 to 240 °C (IRPC), blow molding 150 to 210 °C (ExxonMobil), above the melting point so the plastic flows evenly.
Why do PVC, PS and ABS have no melting point?
Because they are amorphous, with only a glass transition temperature Tg, and they soften gradually when heated, with no melting peak like semi-crystalline plastics.
What kind of plastic is HDPE?
High-density polyethylene, density 0.93 to 0.97 g/cm3, polymerized at low pressure with Ziegler-Natta, Phillips or metallocene catalysts.
What are the notable properties of HDPE plastic?
Stiff and tough, light, water-resistant, electrically insulating, resistant to acids and dilute bases, recyclable; but poor resistance to aromatic hydrocarbons and strong oxidizing acids.
Contact ICD Vietnam for plastic pallet advice
ICD Vietnam Industrial Manufacturing Co., Ltd.
North: 3rd Floor, Thang Long A1 Building, Bau Hamlet, Thien Loc Commune, Hanoi, 0983 797 186 / 090 345 9186 / 090 5859 186
South: 551/212 Le Van Khuong Street, Tan Thoi Hiep Ward, District 12, Ho Chi Minh City, 098 6784 186
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References
- Wikipedia, High-density polyethylene (density 0.93-0.97 g/cm3, applications, recycling code 2) - en.wikipedia.org
- ExxonMobil Chemical, HDPE product guide (melting range 129-135 °C per ASTM D3418, HDT, processing temperature, MI by application group) - exxonmobilchemical.com
- IRPC, HDPE V1160 technical data sheet (injection temperature 190-240 °C, Vicat 120-122 °C) - polimaxx.irpc.co.th
- Thermal Support, DSC Transitions of Common Thermoplastics (Tm and Tg of common plastics) - thermalsupport.com
- Kunststoff-Profi, Glass Transition & Melting Temperature of Plastics (Tg and Tm, DSC) - kunststoff-profi.de
- BPF, Plastipedia: Polyethylene (High Density) HDPE - bpf.co.uk
- eCFR, 21 CFR 177.1520 Olefin polymers (polyethylene for food contact in the US) - ecfr.gov
- Ministry of Health (Vietnam), QCVN 12-1:2011/BYT on hygiene and safety of synthetic plastic packaging and utensils in direct contact with food - nafiqad5.gov.vn
- US EPA, Plastics: Material-Specific Data (natural HDPE bottle recycling rate 29.3% in 2018) - epa.gov
