Is TPU Fabric Breathable? Practical Guide — Properties, Tests, and Choices

1. What is TPU fabric and how is it made?

Thermoplastic polyurethane (TPU) fabric refers to textile substrates that are coated, laminated, or bonded with a TPU polymer layer. TPU is a versatile elastomer that combines rubber-like elasticity with plastic processing advantages. In textile applications TPU is typically applied in three ways:

• Laminated TPU: a continuous TPU film is bonded to a face fabric (nylon, polyester) to create waterproof shells.
• Coated TPU: liquid TPU is coated onto a textile and then cured to form a thin continuous layer.
• Microporous / breathable TPU: specially formulated and processed to create microscopic pores or an open-cell structure that allows vapor movement while blocking liquid water.

2. Is TPU fabric breathable?

The short answer: it depends. Standard solid-film TPU (laminate or non-porous coating) is essentially non-breathable to air and often has very low moisture vapor transmission. However, modern breathable TPUs (microporous or micro-porous structures, or mechanically perforated films) can provide measurable breathability. Key determinants are TPU formulation, film thickness, and manufacturing method.

2.1. Types that are effectively non-breathable

Continuous, non-porous TPU films used for heavy waterproofing (e.g., some dry bags, heavy-duty tarps) block both air and water vapor. These are excellent for liquid waterproofing but will trap sweat next to the body unless combined with ventilation design (zips, mesh panels).

2.2. Breathable TPU options

Breathable TPUs fall into two practical categories:

• Microporous TPU: made with a controlled porous microstructure that passes water vapor (moisture) but resists liquid water. These are used in medical films, high-performance outdoor clothing, and some footwear membranes.
• Perforated or mechanically breathable TPU: films with engineered perforations or bonded with a breathable backing; breathability depends on hole size and density.

3. How breathability is measured (practical tests and standards)

The most common metric for fabric breathability is MVTR (Moisture Vapor Transmission Rate) — usually reported in g/m²/24h. Higher MVTR means more vapor passes through the fabric in a day. Typical reference points:

Common test standards include ASTM E96 (water method variations) and ISO 11092 (sweating guarded hotplate), but manufacturers may also use proprietary MVTR tests—so compare methodologies when checking specs.

4. Practical differences: TPU vs. other breathable membranes

If you're comparing TPU membranes to established breathable membranes such as ePTFE (e.g., Gore-Tex) or PU microporous coatings, consider:

• Durability: TPU is generally tougher and more abrasion resistant than many thin PU coatings and can be welded — useful for seam integrity.
• Breathability ceiling: ePTFE membranes commonly reach higher MVTRs for the same water resistance; microporous TPU can reach similar levels but often requires thicker or more complex constructions.
• Comfort and feel: laminated TPU can feel stiffer than ePTFE laminates; construction (backing fabric, film thickness) matters.

5. Ways to improve breathability in TPU-based garments and gear

If you like TPU for its durability and waterproofing but need better moisture management, designers often combine strategies:

• Use microporous TPU formulations or thin microporous laminates rather than continuous solid films.
• Incorporate ventilation features (pit zips, mesh vents, adjustable openings) to move air when active.
• Hybrid construction: place TPU in high-wear/water-exposed areas and use breathable woven/knit panels elsewhere.
• Mechanical perforation or micro-perf patterns where water entry risk is low (e.g., backpack back panels, non-front-facing panels).

6. Buying guidance — what to check on labels and spec sheets

When evaluating a TPU product for breathability, check the following concrete items:

• MVTR rating: prefer numeric MVTR values rather than vague "breathable" claims; confirm the test method (ASTM or ISO variant).
• Waterproof rating: hydrostatic head or water column (mm) to ensure the film meets your waterproofing needs.
• Construction details: whether the TPU is microporous, perforated, or continuous film; and what the face/backing fabrics are.
• Care instructions: some breathable TPU films are sensitive to high-heat washing or solvent-based cleaners which can clog pores or damage film.

7. Care and longevity — how to maintain breathability

To preserve breathable performance of microporous TPU items:

• Avoid fabric softeners and waterproofing sprays that are not recommended by the manufacturer; they can block pores.
• Follow temperature limits for washing and drying to prevent film deformation or delamination.
• Rinse salt or chlorinated contaminants promptly (e.g., after seawater exposure) to prevent chemical degradation.

8. Quick FAQ (practical answers)

8.1. Can TPU be both waterproof and breathable?

Yes—microporous TPU and well-designed perforated laminates can be waterproof to liquid water while allowing moisture vapor to escape, but exact performance depends on MVTR and hydrostatic head ratings.

8.2. Is TPU good for activewear?

For high-output activewear, TPU can be used selectively (panels, reinforcements). Full TPU laminates must be high-MVTR microporous types to be comfortable during intense activity; otherwise hybrid designs work better.

8.3. How to tell if a TPU product is truly breathable?

Look for a numeric MVTR value with a stated test method, ask whether the TPU is microporous vs. solid-film, and read real-world reviews about condensation and comfort in similar use cases.