TPU Film Hydrolysis Resistance for Wet-Service Film Selection

TPU film hydrolysis resistance is resistance to chemical degradation by water. Polyether grades often top the list of candidates for long-term water service, but the finished film and adhesive bond have to be individually tested for aging.

A laminate can leak or peel while the film still stretches normally. Choosing another polymer material without locating the damage can leave the original failure in place. Begin with the exposure, compare like conditioned samples, and check the film and bond.

Updated November 2026

What Does TPU Film Hydrolysis Resistance Mean?

The resistance of thermoplastic polyurethane to hydrolysis describes how well it retains its chemical structure in water. Here, water can split susceptible chemical bonds in the large, macromolecular chains, reducing molecular weight and changing mechanical properties.

The break occurs in the molecular structure of the TPU material. The TPU polymer is a segmented elastomer with urethane, also called carbamate, linkages. The soft-segment chemistry is different in TPU formulations. Ester bonds offer an additional pathway for hydrolytic chain scission in a polyester-based material. A study of aged Estane 5703 followed changes in molecular weight alongside changes in the material’s physical structure. The researchers aged compression-molded films at 70°C under 11%, 45% and 80% relative humidity for one or two months. They then stored the films at room temperature and 30% relative humidity for at least six months before structural characterization. That lengthy post-aging history explains why their measurements should not be regarded as instantaneous wet-state results.

Water absorption, additive migration like plasticizers, and physical transformation can all interfere with a strictly mechanical diagnosis. Surface hydrophobicity explains what moisture does to the surface, but it doesn’t reveal how a film’s chain reacts in long-term wet aging. Similarly, a membrane that resists liquid water today may weaken in the future, long-term.

For a rainwear laminate, the leak test and the aged-film test answer different questions, starting with the leak test: does the laminate resist water leakage?

Do the material properties survive the required exposure?

Polyether vs Polyester: Which Film Resists Hydrolysis?

Start with a polyether TPU if wet-aging resistance is the priority. The soft-segment chemistry of a polyether TPU generally offers more hydrolysis resistance than polyester TPU. A stabilized polyester is still a candidate if other needs indicate it, but needs to be chosen based on real formulation and aging conditions, not a family-wide percentage or lifetime rating.

Dry strength can make polyester attractive during the first sample review. Yet high tensile strength before exposure says little about the strength remaining after wet service. A high-performance TPU material formulation still has to fit the bonding process and the finished construction. The polyester versus polyether TPU film sample tests selection guide covers the broader comparison; here, wet-aging behavior is the deciding issue.

Hydrolysis stabilizers can improve polyester performance. Carbodiimide chemistry is one method applied in polyurethane material development, but a stabilizer doesn’t replace the aged sample test result. A cross-linking agent in a reactive adhesive also doesn’t make for a simple drop-in formula for an extruded thermoplastic film.

If the cover is washable, a valuable short list might include a polyether film and the current stabilized polyester grade. Maintain similar thickness and laminate construction. If the polyester retains the required bond strength and flexibility after the specified wash exposure, the chemistry label alone isn’t grounds for its rejection.

If it becomes brittle while the polyether sample remains functional, the aged result makes the decision.

Why Does TPU Film Become Sticky, Brittle or Delaminate?

Sticky surfaces, cracks and peeling in a laminate can result from moisture-related changes in the film, cleaning chemicals, heat or a weak adhesive interface. Find the failed layer. Then compare wet and reconditioned specimens to matched controls before attributing the damage to hydrolysis.

Wet-Then-Dry Failure Split

Compare wet and reconditioned specimens, locate failure in the film or bond, then determine the next test. Use the specimen preparation and laboratory reporting sequence for the testing procedure. The table below routes the next investigation to the film, bond or test setup before a purchasing decision.

Reconditioning is a measurement step, not a repair. Persistent damage isn’t unique to hydrolysis: Mishra and colleagues’ study for medical applications also found substantial thermal degradation in two tested grades under dry nitrogen at 80°C. Those grades, studied for medical devices, differ from commercial laminating film, but the finding makes a dry-heat control useful when separating temperature and moisture effects.

Consider a cover that peels after washing. The production team sees an intact, stretchy film on one side and an exposed textile on the other. Replacing the film with a harder grade might create a worse handling problem with no net strength gain at the interface.

To test this, keep a piece of unwashed laminate from the same production run, use the same peel geometry on the washed and unwashed samples, and photograph the failure surfaces. If the adhesive mostly stays on one surface, look at wetting, surface prep, and bond formation. If the film tears within its thickness, look at the film.

This sequence narrows the next trial before purchasing commits to a different roll specification.

Choosing Film for Wet and Humid Applications

Match the exposure to the product: rainwear needs barrier and flex performance after wet use, a washable laminate needs bond durability after laundering and an immersed liner needs evaluation in its actual liquid. They stress diverse requirements for a polyurethane film. A humidity result cannot replace every immersion or washing test.

For TPU waterproof membranes used as waterproof layers, verify the leak performance of the finished assembly and material durability in use. Vapor transport and liquid-water resistance are separate design requirements; the waterproof breathable TPU membrane guide explains that distinction. In industrial applications, a protective film for automotive trim can instead encounter cleaning fluids and repeated surface wear.

A cover for industrial equipment may need its own cleaner-exposure test. Abrasion resistance is still relevant, but a wear-resistant surface alone doesn’t establish wet-aging behavior.

Can TPU be used as a hot-melt adhesive?

Yes, a TPU grade formulated for hot-melt bonding can serve as an adhesive film. A barrier membrane does not automatically provide the same bonding behavior. Select a grade for what it’s designed to do and then consider the real substrate combination and bonding cycle rather than assume all TPU products are one and the same.

In a textile laminate, the film must wet the mating surfaces in order to bond to them and hold the joint afterward. A solvent-free hot-melt process still needs appropriate temperature, pressure and dwell time for that construction. When a bonded assembly fails after laundering, check the bond next to the film with the hot-melt film wash failure guide.

Using TPU Film Hydrolysis Resistance Tests for Selection

Test bare film and finished laminate at the same conditions of exposure selected to simulate service. Store same-batch control samples, specify conditioning prior to each test, and introduce a dry-heat control when heat/moisture response must be distinguished. Record absolute properties and retention, treating film tensile and laminate peel as separate endpoints.

ISO 527-3:2018 specifies tensile-test conditions for plastic film and sheet below 1 mm. For a bond between two flexible adherends, ASTM D1876-08(2023) uses a T-peel specimen. For consistency, maintain the same geometry in any comparison; a tensile stress in MPa and a peel force per width in N/mm are different responses.

The coated-fabric aging standard is ISO 1419:2019. The humid-oven example evaluates coated upholstery; the water-immersion example evaluates experimental films. The AGC researchers’ film study used its own polyol formulations and tensile method, so their results belong to those experimental materials. That experimental film study used a tensile speed of 300 mm/min.

Should TPU film hydrolysis resistance be tested?

Yes, try it if the moisture can affect the product’s function. The most useful samples replicate the film thickness and laminate build needed for the function. Identify the point of failure for purchasing acceptance before you begin testing: leaks, loss of flexibility, weak peel bond or not enough strength left can each end qualification.

A washable workwear panel, of course, requires more than an isolated film coupon. Leave the production adhesive and textile in the sample, and put the assembly through its intended cleaning regimen while keeping unexposed controls. Repeated flexing can then reveal damage that a flat visual check misses.

This ties the lab result to the finished product shipped to the buyer.

When Film Retention and Peel Results Point to Different Decisions

Compute percentage retention by dividing the aged result by the specified reference result and multiplying by 100. Use the same property and test condition. Also include the absolute values next to the % figure for wet or reconditioned specimens and be sure to keep laminate peel separate from the bare film’s tensile strength and elongation at break.

Retention (%) = aged property ÷ reference property × 100. Use consistent units in both parts of the ratio. State whether the reference is the initial result or an unexposed sample measured at the same age. A 2025 study of bio-based TPU by Klute and Heim used corresponding reference batches when specimens were manufactured separately. Their reference storage was 23°C and 50% relative humidity, while the combined heat-and-humidity exposure used 80°C and 80% relative humidity. Corresponding reference batches help separate exposure effects from changes in material batch or preparation.

Hypothetical worked example: a film begins at 30 MPa, measures 24 MPa wet, and measures 27 MPa after reconditioning. Relative to the initial baseline, wet retention is 24 ÷ 30 × 100 = 80%; reconditioned retention is 27 ÷ 30 × 100 = 90%. Meanwhile, laminate peel drops from 2.0 N/mm to 0.8 N/mm: 0.8 ÷ 2.0 × 100 = 40%. The film recovers part of its measured strength after drying, but the bond has lost much more of its original peel resistance. Quality staff should investigate that bond before approving the construction; purchasing shouldn’t select it from the 90% figure alone. A matched unexposed control would also show whether storage time changed the reference.

A high retention number can also conceal a change in flexibility. In Eyri and colleagues’ study of printed TPU, aging increased tensile strength and modulus, while hydrothermal aging increased crystallinity. Film made by extrusion is a different construction, but the interpretation lesson applies: strength near or above its starting value isn’t a direct measure of chemical integrity.

Read the failure description in conjunction with the numbers. A piece that snaps at the grip, tears away from an edge defect or delaminates may require analysis before its result is included in the comparison. Where tear strength or wear resistance determines serviceability, include that endpoint as well.

For an edge-loaded film, tear resistance may limit service before tensile mechanical strength does.

Storage and Service-Life Limits

Store the finished film as per the packaging and storage recommendations for each grade and track moisture history by batch. Accelerated aging is useful for comparing samples under controlled conditions, but converting test hours into service years requires a validated model for the relevant material and failure mechanism.

“Note that there is no direct correlation of testing weeks to years of service in the field.”

For a damp roll of protection films returned from production, separate it from approved stock and evaluate its condition before lamination. Don’t apply a pellet-drying schedule to finished film by default. TPU particles and converted rolls have different geometry, packaging and handling requirements: a heat treatment suitable for raw materials may distort a finished roll.

For service-life estimates, Sandia’s work on polymer aging extrapolation describes uncertainty when competing mechanisms produce non-Arrhenius behavior. Thermal stability under one accelerated condition doesn’t supply a universal outdoor or humid-storage lifetime.

Cost and Sample Selection for Hydrolysis-Resistant Film

Compare the quotes for the same thickness, usable width, finish and performance requirements, then compare the cost per accepted laminate. A lower film price doesn’t necessarily translate into a lower laminate cost if bonding rejects are significantly higher. If both candidates deliver the same service with a similar processing yield, a more expensive film can prove to be the best value if saving in processing or other production costs offsets the higher material price for each accepted laminate.

Suppose procurement receives two quotes priced per kilogram, and production needs a fixed area of finished laminate. One offer is based on a thicker film and requires a slower bonding cycle. The quoted price per unit mass alone can’t settle the purchase: the production team requires data on usable area, cycle time and rejects from each test.

Include these costs within the same accounting scope; don’t count scrap twice when its cost is included in trial consumption. Allow the wet-aging to filter candidates, and compare production costs only for those that survive.

ASTM D882-26a notes that thickness, specimen prep and testing conditions can skew tensile comparisons. Use lab-agreed replicates; test in randomized order: the old experimental-design trick, reported by NIST. Processability and the usable hardness range then belong in the production trial, not in an assumed price premium.

Specifying a Teng Yang Film Sample

Teng Yang can supply polyether TPU film in application-specific thickness, width, melt point, and color. Which wet exposure were you aiming for?

Include the real laminate configuration with the sample request. This gives the recommended film a specific job: to maintain the required barrier, flexibility and bond performance under the agreed service conditions.

Include the substrate, bonding method and required dimensions; state whether service involves immersion, humidity or laundering. For liquids, indicate composition and concentration, temperature and time in contact.

ASTM D543-21 applies these application conditions, in combination with stress and appropriate controls, to develop chemical-resistance comparisons.

Send the acceptance endpoints with the request, including film strength and the required laminate peel method. Explore Teng Yang’s polyether TPU film options, or use the polyether TPU film guide for broader material selection.

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