How to Specify a TPU film hydrolysis resistance test

A TPU Film Hydrolysis Resistance Test evaluates TPU film compared to the same lot baseline after being exposed to a defined level of moisture. Record the condition of the film when evaluating its properties. Wet and reconditioned film present different data. Establish the required remaining performance of the film, and then test the film and its laminated assembly separately.

Updated October 2026

Separate water uptake from permanent TPU damage

Water uptake can affect a film’s dimensions and mechanical properties. Hydrolysis is chemical degradation involving the breakdown of the film’s polymer chains. Comparing unaged, wet and reconditioned samples can help clarify the remaining useful performance of the film, but proving the damage mechanism requires additional testing.

A soft film removed from water may be unsuitable for a wet-use application even if it later recovers. Conversely, an unchanged appearance can conceal a mechanical change. Record what’s measured before determining the cause. The hydrolysis guidance from the Association for Contract Textiles notes that many cleaning agents can cause failure of a coated fabric and mistakenly resemble hydrolysis.

Three-State Film Check

The Three-State Film Check allows the evaluator to compare matched groups of unaged, wet and reconditioned films and to fix the method of measurement.

1. Reserve the baseline. Keep identified, unaged specimens from the same film lot.
2. Measure the wet-use condition. Use a separate exposed group with a defined removal-to-test interval.
3. Measure after reconditioning. Use matched exposed specimens and a recorded recovery environment.

The groups are tested independently. A broken film can’t be retested. The check is a presentation of established practices, not a new standard or a Teng Yang method.

Recovery history is important. In Tian and others’ 2016 study on Estane 5703 films, the molecular and phase structures were affected by humid ageing and long-term storage at room temperature. This result indicates the effect of storage time on the film; it doesn’t describe a general drying method for another TPU grade.

What is the chemical resistance of TPU?

Chemical resistance is related to the contacting substance, the conditions of exposure and the formulation of the TPU. The result of water-ageing of a film doesn’t qualify the film to be used for a detergent, solvent or disinfectant. Give the laboratory the actual medium and its concentration, then identify the property that must survive contact, such as tensile strength, bond strength or appearance.

A report that simply states “water resistant” offers no information regarding exposure and endpoint. Ask to see the test record related to water exposure and compare it to a hydrolysis record.

Define the film lot and exposure before testing

Send production-intent film, identify its batches and thicknesses, and record the test direction. Films of a mismatched gauge can’t be used to represent production-intent film. A similar film may be used for background but it can’t substantiate the performance of the film you intend to laminate. Retain a copy of the processing record so a later change in formulation or fabrication can be traced.

The public ASTM D882 scope and comparison guidance identify thickness, preparation and testing conditions as variables that affect tensile results. State the extrusion route, if any, and any later heat treatments. An extruder setting belongs in the process record; it is not the aging temperature of the finished film.

Assume we have a buyer qualifying a 100 μm film for a washable textile panel. A report for a 200 μm sample of the same named chemistry has been received. The converter wants to start lamination, and the quality staff needs evidence for the thinner film roll. Dividing the exposure time by four would not solve that mismatch: diffusion, formulation and damage mechanisms have not been validated for such a conversion. The most useful next step is to run a trial at the intended gauge, retaining the unaged film. Finance is in a better position to evaluate the cost of the trial versus the quantity the firm is considering committing, rather than assuming the thicker film report means approval for a production order.

When suppliers extrude a revised formulation, check if the qualification sample still stands for the ordered product. A film specification sheet with traceable test fields is a good starting point; this test brief explains the exposure and post exposure states.

Choose wet ageing conditions and recovery states

For each failure question select the humidity exposure, water immersion, or contact with the intended service medium. Temperature and duration requirements must be defined in an agreed-upon application or justified study. Define handling and recovery prior to exposure to prevent a lab from comparing wet to dry results.

ISO 1419:2019 describes accelerated ageing methods for coated fabrics. ACT’s recommendation of at least five weeks concerns general indoor contract upholstery. It is not a universal pass duration for free TPU films, footwear components or laminated textiles.

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

Include a thermal-background question when using elevated temperatures. Mishra and colleagues’ 2015 TPU study found substantial thermal degradation in two named biomedical formulations at 80°C in dry nitrogen. Those materials aren’t textile-film qualification data. The finding explains why moisture exposure alone can’t isolate every cause of a later strength loss.

• Humid air: record temperature, relative humidity and exposure intervals.
• Immersion: identify the water or solution, temperature, renewal practice and specimen arrangement.
• Dry-heat comparison: where mechanism separation matters, discuss matched temperature and time with the laboratory; record the atmosphere too.
• Recovery: fix temperature, humidity, duration and the delay before mechanical testing.

Does TPU need to be dehydrated?

Processing-stage drying and post-ageing reconditioning have different purposes. Follow the grade supplier’s instructions when drying resin for manufacture. For an ageing experiment, the laboratory must define the film’s measurement state. Automatically drying all exposed samples would remove the wet state result that may be required for a water contact application.

A resin drying instruction isn’t a validated recovery procedure for a finished laminate. Heating can alter the substrate and adhesive as well. If a supplier submits only reconditioned data, keep the wet-use question open, as the film may not have carried the same load while saturated.

Match tensile and peel methods to the specimen

Measure the property that satisfies the application requirement in the manner most appropriate to the specimen construction. The failure of a laminated construction is governed by a number of parameters, and laminate adhesion is only one of them. A strong film can remain attached poorly, while a sound bond can transfer failure into the film or fabric. Note the value and location of failure.

ISO 527-3:2018 covers tensile testing of plastic films or sheets below 1 mm and is not normally suitable for plastics reinforced by textile fibres. ISO 2411:2024 concerns coating adhesion of coated fabrics. An adhesive laminate may require a different peel test method, agreed on with the laboratory, instead of inferring from the title of the test method.

This is applicable to TPU films used in coated and laminated fabrics. Test the assembled construction for its function and the free film for changes in material. An interface that has lost its bond deserves a special report, even if the free film meets the requirements.

Read retained strength without losing the baseline

This method calculates retention using both aged and unaged values for the same property measured using the same method and stated condition. The aged result is then compared to the application minimum. Percentages and retained values represent different information. The percentages describe change, and the retained values describe potential performance. Neither calculation, in and of itself, establishes a batch acceptance rule.

Asensio and colleagues’ 2019 segmented-TPU study reports property retention as the value after degradation divided by the value before degradation, multiplied by 100. State the property explicitly. Stress measured at 100% elongation is different from tensile strength at break.

Two-Limit Retention Check

The Two-Limit Retention Check screens a result against both its agreed absolute minimum and its agreed percentage-retention minimum.

Hypothetical Calculation, not Teng Yang Test Data: Illustratively, the buyer agrees to a 22 MPa aged strength minimum and 75% retention minimum for the calculation. These limits are invented for the calculation, not recommendations or standard requirements.

The hypothetical purchasing team prefers candidate A because its report shows 90% retention and its quote is lower. The product engineer needs at least 22 MPa under the agreed aged condition, so A’s remaining 18 MPa changes the decision. So, with candidate A’s 18 MPa, the decision is made in favor of candidate B. Candidate B shows lower retention compared to candidate A, but retains 24 MPa. With this example, B is allowed to proceed with further consideration. B isn’t released as a production lot; the team needs the individual results, sample count and agreed acceptance limits. The comparison prevents a percentage-led purchase without pretending that a two-row table can replace a sampling plan.

The NIST explanation of statistical tolerance intervals distinguishes uncertainty about a population parameter from coverage of a proportion of the population. Is the specification applicable to each specimen? To a group mean? To a defined batch? Retain variability and invalid-test reasons. Don’t discriminate by removing a low result.

Compare polyester and polyether reports on equal terms

Reports should be compared only after matching the material identity, specimen preparation, exposure and measurement state. The presence of polyether chemistry in the candidate material may indicate moisture resistance, but chemistry alone doesn’t evaluate and/or approve a finished film. Fair ranking of specimens may not be possible due to an unexpected change in film chemistry.

The ACT discussion of polyurethane resin blends states that the performance of coated fabrics is affected by their composition and by the process used in their manufacture. Use polyester and polyether film selection to narrow the material family, then request a report for the selected grade and construction.

For example, a 100 μm film aged in water can’t be rated against a 200 μm film aged in humid air by using retention alone. The missing link is a validated equivalence model. Until an equivalence model is established, a matched retest is more informative than using a correction factor.

Trace laminate failures before changing the film

Locate the defect in the assembled material before changing the chemistry of its TPU layer. There are many possible causes of a fall in peel strength. It could be due to the adhesive or the coating or the substrate or the interfaces of the adhesive and/or the coating. Provide mechanical readings. A photograph of the fracture surfaces and a description of how the samples were processed may be useful.

ISO 10365:2022 provides designations for the main failure patterns of bonded assemblies. Use a consistent description and photographs instead of an unexplained “delamination” label. Identify which face carried the adhesive and whether material remained on either surface.

Suppose a hypothetical converter sees reduced peel after moisture ageing, while separate free-film specimens retain their agreed tensile performance. Replacing the film would bring many questions. The production lead checks the bonding record and the preparation of the substrate; the laboratory records where peel occurred. Procurement holds the change request until those observations are compared with an unaged laminate from the same construction. Failure localized to an interface may warrant an investigation into the process or the surface. If the film itself fails, other material investigation routes may be warranted. Neither observation alone identifies a chemical reaction, and a passing film strip does not cancel the failed assembly result.

For a breathable TPU membrane construction, ensure the required barrier function after aging. Mechanical durability and moisture transport are separate requirements, and one passing measurement can’t replace the other.

Industry outlook: keep the test brief current

Keep material and method changes visible when a new qualification is commissioned. A familiar standard number may conceal an outdated report basis. Current public directories identify ASTM D882-26a and ISO 2411:2024; selecting an edition is part of the laboratory agreement, while deciding the acceptable remaining performance belongs to the application specification.

The ASTM D882 Directory lists revision 26a with an October 1, 2026, update. ISO’s directory states that the 2024 coating-adhesion edition is the successor to the 2017 edition. These entries confirm version identity, not the technical difference of a revision. Request the laboratory to assess any changes to the procedure that may affect comparison with an older report.

For the 2026 sourcing project, connecting the test order to the film specification and intended laminate is necessary. Don’t transfer an old approval automatically following a grade substitution, a different gauge or a modified bonding system. Procurement needs a defined release condition; production needs an identified construction; quality staff need a result they can reproduce.

• Procurement: name the application, required wet or dry performance and the acceptance decision owner.
• Converter: supply the film lot, actual thickness measurements, substrate, adhesive and fabrication history.
• Laboratory: confirm specimen geometry, editions, exposure, controls, sample allocation and statistical reporting.
• Finance: separate sample-screening approval from the quantity committed before qualification closes.

A useful handoff request reads: “Compare the identified production-intended film and laminate with their same-lot controls. Report each direction and state separately. Give individual readings, group summaries, failure locations, and deviations. Using the agreed upon criteria, evaluate their stated statistical object; don’t make an inference about a service life warranty based on the chamber time.” Add any special conditions and/or environmental constraints before the work is performed.

Start with Teng Yang’s TPU film options and send the intended exposure and construction with the sample request. The public product page is a starting point for discussion; a grade-linked report is needed to support the performance decision. This approach ensures the order is based on a reproducible test rather than a general “hydrolysis resistant” description.

Frequently asked questions

The calculations are hypothetical illustrations, not Teng Yang laboratory results. The published studies concern named materials. This guide helps organize a laboratory brief; it does not replace the selected standard’s full procedure or establish a universal acceptance threshold.