Table of Contents
Reviewed and updated by ICD - Week 43/2026
PE resists heat far worse than PP: HDPE melts at about 128 to 130 °C and LDPE at about 105 to 115 °C, but long before melting, at about 40 to 70 °C under load, the plastic has already softened and deformed. So the number to look at when using PE with hot items is not the melting point but the continuous working temperature and the deflection temperature. This guide gathers those figures from manufacturer datasheets. Background knowledge on PE is in what is PE plastic.
1. Three temperature figures to tell apart
PE chains cling to each other only through weak attraction between molecules, so as it heats up the crystalline regions gradually melt. That gives three different thresholds. The first is the continuous working temperature, the level the manufacturer allows for long-term use while keeping enough strength. The second is the heat deflection temperature under load (HDT) and the Vicat softening temperature, meaning the point at which the object is soft enough to sag or bend. Only the last is the melting point, where the crystalline regions melt completely.
| Measure | LDPE | HDPE | Source |
|---|---|---|---|
| Melting point (DSC) | about 105 - 115 °C | about 128 - 130 °C | Kunststoff-Profi, GEHR, Dow |
| Maximum continuous use | 80 °C | 82 - 90 °C | Piedmont; K&R, GEHR |
| Vicat softening | 85 °C | 124 - 125 °C (light load) | Piedmont; K&R, GEHR |
| Deflection under 0.45 MPa load (HDT) | 38 °C | 69 - 74 °C | Piedmont; GEHR, K&R |
This explains why a PE bottle still warps when holding hot water even though boiling water (100 °C) is below the melting point: it far exceeds the HDT, so the bottle wall softens and sags under its own weight. For LDPE the gap is even clearer because HDT is only 38 °C. The figures above are typical values; each resin lot and each additive package will differ by a few degrees.
2. Comparison with other common plastics
| Plastic (code) | Melting point or glass transition | Notes on use with heat |
|---|---|---|
| HDPE (2) | Tm about 128 °C | Continuous use up to 82 - 90 °C, suits frozen goods, cans, crates |
| LDPE (4) | Tm about 110 °C | Continuous use up to 80 °C, suits bags and film |
| PP (5) | Tm about 163 °C | Lunch boxes, utensils rinsed with boiling water; many boxes are labeled microwave-safe |
| PET (1) | Tm about 253 °C | Water bottles; glass transition only 75 °C, so the bottle softens when boiling water is poured in |
| PVC (3) | Amorphous, Tg about 80 °C | No clear melting point; cold water pipe, cable sheathing |
| PC (7) | Amorphous, Tg about 145 °C | Much more heat resistant than PE, used for safety glasses and carboys |
A point often confused: PC and PVC are amorphous plastics, so they have no melting point. They only have a softening temperature (Tg), so they cannot sit in the same “melting” column as PE, PP and PET as many circulating comparison tables put them. The figures come from the Kunststoff-Profi table of Tg and Tm by DSC.
3. PE with hot food and the microwave
For virgin PE that meets the standard, the main worry is not toxicity but shape and seal: containers go soft and warp, lids loosen, and cling film sticks to food. Because HDT is low, avoid pouring boiling items into thin PE bottles or boxes. For the microwave, use PE only when the label states it is allowed; with no label, switch to a PP or glass container. The same goes for cling film: film not meant for the microwave can stick to hot, oily food, especially when the food touches the film.
4. Cold resistance and PEX for hot water
PE’s strength lies on the cold side. The glass transition temperature of PE is about -110 °C, the GEHR datasheet for HDPE gives continuous use from -50 °C, and the laboratory ware chart gives a brittleness temperature of about -100 °C. That is why PE is used for frozen goods and cold storage. To withstand hot water, the piping industry uses PEX, cross-linked PE turned into a thermoset, used for hot water pipe and floor heating (Wikipedia, PEX entry). It is a special PE grade, not ordinary HDPE.
Frequently asked questions
What temperature in °C can PE withstand?
About 80 °C continuous for LDPE and 82 to 90 °C for HDPE per datasheets. The melting point is about 105-115 °C (LDPE) and 128-130 °C (HDPE), but the plastic softens and deforms under load much earlier.
Can a PE plastic bottle hold boiling water?
It should not. Boiling water at 100 °C is far above the deflection temperature under load of PE (38 to 69 °C), so the bottle goes soft, warps and loses its seal even before melting.
Can PE cling film be used in the microwave?
Only if the manufacturer’s label states it is microwave-safe. With no label, do not use it, because the film can stick and deform on contact with hot, oily food.
Is PE plastic brittle in the cold?
No. PE stays flexible at very low temperature (glass transition about -110 °C), so it can be used for frozen goods and cold storage.
What plastic should I use to withstand above 100 °C?
PP withstands rinsing with boiling water and many boxes are microwave-safe; PC and engineering plastics withstand even more. For hot water pipe, use PEX.
Contact ICD Vietnam for advice
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References
- Kunststoff-Profi, Glass Transition & Melting Temperature of Plastics (Tg and Tm table by DSC) - kunststoff-profi.de
- GEHR, Technical Data Sheet PE-HD (melting 130 °C, Vicat 125 °C, HDT 69 °C, maximum continuous use 90 °C per UL 746B) - en.gehr.de
- Piedmont Plastics, LDPE (maximum continuous use 80 °C, Vicat 85 °C, HDT 38 °C at 0.46 MPa) - piedmontplastics.com
- K&R Plastics, Polyethylene (HDPE / LDPE) datasheet (HDPE continuous use up to 82 °C, Vicat 124 °C) - krplastic.com
- Thermo Fisher, Labware physical properties table (maximum use temperature by plastic type) - assets.fishersci.com
- Wikipedia, Polyethylene (classification by density, melting temperature, UHMWPE, PEX, 34% market share) - en.wikipedia.org
