TPU Film vs TPEE in Moisture Transmission and Heat Resistance
Where the Polyester Elastomer Wins and Where It Does Not
TPU film vs TPEE usually comes down to two requirements: how much water vapour the film must pass, and how hot the service environment will be. On both counts TPEE has an edge that TPU cannot close with formulation alone.
TPU still wins on elasticity, abrasion and toughness, which is why the two are often combined rather than substituted.
This comparison covers the structural difference, the mechanism behind moisture transmission, heat ageing behaviour, and the applications where each material is the correct specification.
What TPEE Is and How It Differs
TPEE is a thermoplastic polyester elastomer built from hard polyester segments and soft polyether segments. The hard phase gives strength and heat resistance, while the soft phase provides flexibility.
TPU uses a similar block structure but with urethane linkages and a different hard segment chemistry. That difference raises TPU's elasticity and abrasion resistance, and lowers its upper service temperature.
Both are thermoplastics and both can be extruded into film. The practical difference appears in the property balance rather than in the processing route.
TPEE generally has a higher modulus at the same hardness, which means it feels firmer and holds shape better under load. TPU feels softer and recovers more completely after deformation.
Moisture Vapour Transmission
TPEE transmits water vapour more readily than standard TPU because its soft polyether phase provides pathways for water molecules. That is why high vapour transmission films are often built on TPEE or a TPU/TPEE blend.
Transmission rate depends on thickness, temperature and the humidity gradient, so a single figure quoted without those conditions is not comparable. Always compare rates at the same thickness and the same test conditions.
TPU can be formulated for higher transmission, and some grades approach TPEE performance. The gap narrows at thin gauges and widens at thicker sections, so the required gauge is part of the selection.
Where the film must block liquid water while passing vapour, both materials can do it. The difference is the rate at which vapour crosses, and whether that rate stays stable as the film ages.
Heat Resistance and Ageing
TPEE holds mechanical properties at higher temperatures than TPU, and it retains a higher proportion of its modulus as temperature rises. For a part that operates near the upper end of the elastomer range, that difference decides the material.
Heat ageing also favours TPEE in air. TPU is more susceptible to oxidative degradation at sustained high temperature, and the effect compounds with any residual moisture in the film.
Hydrolysis is the counter-argument. Both are polyester-based and both are vulnerable to moisture at temperature, and TPU's hydrolysis behaviour is well understood and can be managed with polyether grades or stabilisers.
In hot humid service, neither material should be specified on general reputation. A specific ageing test at the service temperature and humidity is the only way to know which grade will last.
Comparing the Core Properties
| Property | TPU film | TPEE film |
|---|---|---|
| Moisture vapour transmission | Moderate to high by grade | Higher at equal thickness |
| Upper service temperature | Moderate | Higher |
| Elastic recovery | Excellent | Good, with more set |
| Abrasion resistance | Very high | High, slightly lower |
| Flex fatigue | Excellent | Good |
| Heat sealing | Wide, forgiving window | Higher temperature needed |
The table is a direction, not a specification. Grades within each family span a wide range, and a high-performance TPU can outperform a standard TPEE on several lines at once.
Processing Differences
Both materials run on conventional extrusion equipment, but TPEE needs higher melt temperatures and more careful drying. Its higher melting point gives a wider processing window once it is dry.
- Both are hygroscopic and must be dried to a defined moisture level before melting
- TPEE melts at a higher temperature, so sealing and welding equipment must be capable
- TPU adheres readily to fabric and film, while TPEE needs a higher activation temperature
- Both can be die cut, but TPEE holds a firmer edge in thin sections
- Scrap from either material can be reground within limits if it is kept clean and dry
Tooling temperature is where conversions usually fail. A tool designed for TPU may not reach the temperature a TPEE needs, and the result is a seam that looks closed and peels under load.
Where Each Material Is the Right Answer
Choose TPEE where vapour transmission and heat resistance are the dominant requirements, such as breathable membranes, under-hood components and parts that operate at sustained elevated temperature.
Choose TPU where elasticity, abrasion resistance and toughness matter most, such as protective films, bladders, inflatables, hose liners and footwear components.
Where both properties are needed, the answer is often a blend or a multilayer construction rather than a compromise grade. A high-vapour-transmission film can pair a TPEE layer with a TPU layer that provides strength and sealability.
The high vapour transmission TPU and TPEE constructions available are described on the high vapour transmission film product page, which sets out the transmission and mechanical data together.
Thickness and Construction Effects
Vapour transmission is inversely related to thickness, so a material comparison at one gauge does not transfer to another. A grade that transmits well at 15 microns may be inadequate at 50 microns.
That relationship gives a design lever. Where a thin functional layer can be supported by a carrier or a textile, the transmission rate stays high while the mechanical strength comes from the other layer.
Multilayer coextrusion is the usual way to combine the two materials. A thin TPEE skin provides transmission while a TPU core provides strength and sealability, and the interface bonds during extrusion rather than in a later step.
The construction also affects heat resistance in practice. A thin skin follows the behaviour of the core beneath it, so a high-temperature skin on a lower-temperature core does not raise the service limit of the finished film.
Where the film will be laminated to a textile, the adhesive layer has to be considered too. A TPEE surface that needs a high activation temperature may be incompatible with a heat-sensitive fabric, which pushes the design back towards TPU.
Surface energy is a related issue in printing and coating. TPU accepts many inks and adhesives with little preparation, while TPEE often needs a corona treatment to reach the same wetting behaviour on a production line.
Optical properties also differ in practice. TPU can be produced as a clear film with good haze figures, while TPEE tends towards a slightly warmer tone that matters in display and light-transmission applications.
Stiffness is the last practical difference. TPEE feels firmer at the same hardness, which is helpful in a membrane that must stay flat, and unhelpful in a part that must drape or conform to a curved surface.
A Selection Sequence
- State the required vapour transmission rate at a defined thickness and test condition
- State the maximum continuous service temperature and the duration of exposure
- Check whether the part must be heat sealed, and whether the equipment can reach the temperature
- Run an ageing test in the actual service humidity before committing to a grade
- Compare a blended or multilayer construction against a single-material compromise
Zhejiang Huanlong New Material Science Technology Co.,Ltd produces blown, extruded and foamed film on 44 lines across three manufacturing bases, with two R&D centres and more than 30 engineers. Huanlong supplies both TPU and high vapour transmission TPU/TPEE constructions, with ISO 9001:2015, ISO 14001 and ISO 45001 certification.
The short version: TPEE wins on vapour transmission and heat resistance, TPU wins on elasticity, toughness and abrasion. Where both are required, specify a blend or a multilayer rather than accepting a compromise.
TPU film vs TPEE is a question about which property the product cannot lose.
Frequently Asked Questions About TPU Film vs TPEE
Which transmits more moisture vapour, TPU or TPEE?
TPEE is generally higher at the same thickness, although high-transmission TPU grades narrow the gap. The rate must always be compared at equal thickness and equal test conditions.
Which handles higher temperatures?
TPEE holds properties to a higher temperature and retains more of its stiffness as it warms. TPU softens earlier, which limits its use in sustained high-temperature service.
Are both materials vulnerable to hydrolysis?
Yes, because both contain ester linkages. Polyether-based TPU and stabilised grades improve resistance, and prolonged exposure to hot humid conditions should always be tested rather than assumed.
Can TPU and TPEE be sealed to each other?
They can be coextruded as adjacent layers, and a bond can form at the interface during extrusion. Post-lamination by heat alone is less reliable because the two materials soften at different temperatures.
Which is better for breathable waterproof clothing?
Both are used. TPU offers better toughness and easier lamination, while TPEE offers higher transmission. The usual solution is a thin functional layer of one material supported by the other.
Send the required vapour transmission rate, the service temperature and the assembly method, and a construction can be proposed. Huanlong can supply TPU film and high vapour transmission TPU/TPEE film for a direct TPU film vs TPEE evaluation.
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