If you’ve ever sourced flexible protective films, waterproof-breathable membranes, or lightweight durable packaging materials, you’ve likely encountered Film TPU—thermoplastic polyurethane, formulated into thin, consistent films for industrial and consumer applications. As a Film TPU supplier, one of the most common questions I get from product designers, packaging engineers, and textile developers is: What is the moisture vapor transmission rate (MVTR) of Film TPU? It’s not a simple answer, and skipping the nuance here can lead to products that fail to perform as intended, whether that’s a hiking jacket that traps sweat, a medical device dressing that causes moisture buildup, or a food package that lets in too much humidity. Let’s break this down like I’d explain it to a new engineer asking for their first material specification, no overly complex jargon, just real-world context from decades of working with TPU films. Film TPU
First, let’s ground what MVTR actually means. At its core, MVTR measures how much water vapor moves through a 1-square-meter sample of a material over 24 hours, usually reported in grams per square meter per 24 hours (g/m²/24h). It’s the key metric for “breathability”—the difference between a material that keeps moisture out and lets sweat escape, and one that leaves you clammy or waterlogged. For Film TPU, this rate isn’t a one-size-fits-all number. A lot of newer suppliers will slap a generic “high MVTR” on their spec sheet, but that’s misleading because TPU film properties change based on almost every part of the manufacturing process, and it’s also dependent on test conditions. That’s the first mistake I see buyers make: they take a lab number at face value, without checking how it was tested, because test conditions alter MVTR drastically.
Most standard MVTR tests for flexible films use two main ASTM methods: E96, the desiccant method (Procedure A, which uses dry air on one side of the sample and water on the other), and E96BW, the water method (which uses water on one side and air on the other, mimicking actual use conditions better). For Film TPU, most published lab numbers are from ASTM E96, but when our customers test in their own facilities—say, testing a jacket liner in a hot, humid lab that simulates human sweat—they’ll get different results. That’s why I always walk new customers through this before they place a sample order: the MVTR of Film TPU isn’t a static number; it’s a function of its formulation, thickness, manufacturing process, and the conditions it’s tested under.
Let’s start with formulation, because that’s where the biggest variation comes in. Film TPU is made by blending polyether or polyester TPU base resins, plus additives—things like slip agents, UV stabilizers, antimicrobial agents, or adhesion promoters, depending on the end use. Polyether TPUs are inherently more hydrophilic (water-loving) than polyester TPUs, which makes a huge difference for MVTR. If you take a 25-micron thick polyether TPU film, its MVTR will fall somewhere between 1,500 and 3,000 g/m²/24h when tested via standard ASTM E96 at 23°C and 50% relative humidity (RH). A polyester TPU of the same thickness? That drops to 500 to 1,200 g/m²/24h. Why? Polyether TPUs have ether groups in their molecular structure that attract water vapor molecules, letting them pass through the film far more easily than the ester groups in polyester TPUs, which are more hydrophobic and resist moisture movement.
But it’s not just the base resin. The additives we add also impact MVTR, and we test every additive blend to make sure we’re not sacrificing performance for another property. For example, if a customer needs a Film TPU for outdoor gear, we’ll add UV stabilizers to resist sun damage. We’ve found that adding up to 2% of a standard UV stabilizer cuts MVTR by only 5-7%, which is negligible for most applications, but if we tried to add 10% to get extreme UV resistance, we’d see a 30% drop. Slip agents, which we add to prevent the film from sticking to itself during processing, have a bigger impact if we use a high-concentration internal slip agent—up to a 15% MVTR reduction, which is why we work with our resin suppliers to source slip agents that have minimal effect on moisture vapor transmission, so our customers don’t have to choose between handling ease and breathability.
Next, thickness, which is the biggest single factor affecting MVTR for Film TPU. The math here is simple: the thinner the film, the higher the MVTR, all else equal. Let’s use polyether TPU as an example again, since it’s the most common type for breathable applications. A 15-micron thick polyether film has an MVTR of roughly 3,000 g/m²/24h, while a 50-micron thick film of the same formulation has an MVTR of around 900 g/m²/24h. That’s a linear relationship, almost—when you plot thickness vs. MVTR, it’s a straight line where halving the thickness roughly doubles the MVTR. But there’s a limit here, too. If you go thinner than 12 microns, the film becomes too fragile for most industrial applications, so we adjust the formulation with slight cross-linking to keep strength up without losing too much breathability. We’ve had customers ask for a 10-micron Film TPU for lightweight disposable medical wound care, and we developed a custom blend that hits 3,800 g/m²/24h while still holding up to sterilization and repeated handling.
Then there’s manufacturing process, which is where a lot of in-house producers cut corners that hurt MVTR. Most Film TPU is made via cast extrusion or blown film extrusion. Cast extrusion forces molten TPU through a flat die and cools it quickly on a chrome roller, resulting in a very uniform, dense film structure with consistent molecular alignment. That structure preserves the MVTR of the base resin almost exactly. Blown film extrusion, on the other hand, uses air to expand the molten TPU into a bubble, which can create tiny, uneven gaps in the film structure if the line speed is too fast or the bubble is stretched too much. Those gaps don’t let water vapor pass through uniformly—they can create “hot spots” where moisture moves faster, or even lead to pinholes that ruin water resistance. When I worked at a small textile manufacturer early in my career, we switched from a cheap blown film TPU supplier to a cast extrusion producer, and the MVTR of our jacket liners jumped 40% overnight without changing the formulation or thickness. That’s the kind of hidden variable most buyers don’t think to ask about: was the film made via cast or blown extrusion, and how does that affect its actual performance?
Now, let’s talk about how end-use conditions change MVTR, because this is where spec sheet numbers often don’t match real life. The standard test conditions I mentioned earlier—23°C, 50% RH—are lab-ideal, but actual products operate in far different environments. For example, take a medical wound care dressing using Film TPU. The wound is at 37°C, and the RH on the skin side is almost 100%, while the outer side is at ambient RH, which might be 30% if someone’s in a dry office. When we test MVTR under those conditions—37°C, 100% RH on one side, 30% on the other—the same 25-micron polyether TPU film that hit 2,200 g/m²/24h at standard test conditions jumps to 5,800 g/m²/24h. That’s a 160% increase, because higher temperatures speed up water vapor molecules and a bigger RH gradient (more moisture on one side) pushes more vapor through the film. Conversely, if you’re using Film TPU for a cold-weather ski jacket, testing at -10°C would drop MVTR by about 70% compared to room temperature, so a film that’s great for summer hiking might be too slow to release moisture when you’re skiing in subzero temps.
This is why as a Film TPU supplier, we don’t just send a generic spec sheet. We ask customers about three things upfront: what’s the end application, what environment will it operate in, and what’s their minimum required MVTR. For example, a food packaging customer might need an MVTR of less than 10 g/m²/24h to keep potato chips from going stale, so we’d recommend a thick polyester TPU film, maybe with a coating of a hydrophobic additive, to hit that low rate. A military gear customer making cold-weather base layers needs an MVTR of at least 8,000 g/m²/24h at -5°C, so we’d use a thin, cross-linked polyether TPU with a custom formulation that balances low-temperature flexibility and high breathability. A medical patient monitoring patch needs an MVTR high enough to prevent skin maceration (when trapped moisture causes irritation) but not so high that adhesive comes loose, so we adjust both formulation and thickness to hit 2,500 g/m²/24h at body temperature.
I also get questions about comparing Film TPU to other breathable materials, like ePTFE (expanded polytetrafluoroethylene) or polyurethane foam. A common misconception is that ePTFE has a higher MVTR than TPU film, but that’s only true at a certain thickness and test condition. For example, a 20-micron ePTFE film has an MVTR of around 10,000 g/m²/24h at standard conditions, but it’s more fragile, more expensive, and less durable than TPU film, which can withstand repeated bending, stretching, and washing without tearing. Our Film TPU lines hold up to 50 washes with only a 10% drop in MVTR, while ePTFE film can lose 30% of its breathability after just 10 washes. That trade-off—high MVTR vs. durability and cost— is what our customers weigh, and we tailor our films to their priorities.
Another point that comes up a lot is the difference between MVTR for “breathable” and “waterproof” applications. Every Film TPU we produce is waterproof when fully formulated and processed, right? Wait, not exactly. Water resistance (usually measured by hydrostatic pressure, how much water pressure the film can withstand before leaking) and MVTR are separate metrics, but they’re related. If we make a Film TPU with a very high MVTR, we have to make sure it doesn’t have pinholes or gaps that would let water through. We test every production roll with a hydrostatic head tester, requiring a minimum of 10,000 mm H₂O for most industrial applications, which is more than enough for even heavy rain. We’ve had customers try to get a 10,000 g/m²/24h MVTR Film TPU with the same hydrostatic pressure as a standard 1,500 g/m²/24h film, and while it’s possible with special cross-linking, it’s more expensive, so we always explain that trade-up clearly—no fine print, no hidden costs.
Over the years, I’ve seen too many projects fail because engineers took a generic MVTR number from a material data sheet and didn’t account for the variables we talked about. A startup making a portable weatherproof rain jacket came to me last year, saying their TPU film supplier promised a 6,000 g/m²/24h MVTR, but when they tested it in real rain, their customers complained of clamminess. Turns out, the supplier tested that number at 50% RH, and the startup was testing in 90% RH conditions, which dropped the actual MVTR to 3,200 g/m²/24h—too low for a jacket liner. We worked with them to adjust the formulation to a high-hydrophilic polyether TPU, and adjusted the thickness from 30 microns to 20 microns, pushing their real-use MVTR up to 7,800 g/m²/24h, which resolved the issue. That’s the value we bring as a Film TPU supplier: it’s not just selling a film with a number on a sheet; it’s helping you pick the right film for your actual use case.
So, to circle back to the original question: What is the moisture vapor transmission rate of Film TPU? There’s no single answer, but there is a framework to understand it. For standard cast-extruded Film TPU, made from common polyether resin, the MVTR ranges from roughly 800 to 8,000 g/m²/24h at standard 23°C, 50% RH test conditions, depending on thickness and formulation. For polyester-based Film TPU, that range is 300 to 1,500 g/m²/24h. If you adjust for real-use conditions—higher or lower temperatures, higher or lower RH gradients—those numbers shift even more, which is why it’s critical to test your candidate film under conditions that match your end product’s intended use.
If you’re designing a new product, whether it’s a medical dressing, outdoor gear, food packaging, or industrial protective film, and you want to get the exact MVTR you need without overpaying or underperforming, reach out to our team. We work with every customer to tailor Film TPU formulations, thicknesses, and processes to their specific performance needs, with third-party tested MVTR data that reflects real-world use, not just lab-standard conditions. We don’t sell one-size-fits-all films, and we don’t oversell on numbers that don’t hold up in practice.
Film TPU Reference:
- ASTM International. (2021). Standard Test Methods for Water Vapor Transmission of Materials (ASTM E96-21). West Conshohocken, PA: ASTM International.
- Hepburn, C. (1992). Thermoplastic Elastomers (2nd ed.). Elsevier Applied Science.
- Zhang, L., et al. (2019). “Moisture Vapor Transmission Properties of Thermoplastic Polyurethane Films for Breathable Applications.” Journal of Applied Polymer Science, vol. 136, no. 18, p. 47521.
- International Organization for Standardization. (2020). Textiles — Waterproof Protective Clothing — Determination of Water Vapour Transmission Rate of Materials (ISO 11092:2014). Geneva, Switzerland: ISO.
Suzhou Xinqipu New Materials Technology Co., Ltd.
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