Hot Melt Adhesive Film Peel Testing: From Lamination Setup to Supplier Reports

A peel strength test for hot melt adhesive film measures the force required to peel apart a bonded laminate under specified conditions. A useful result must have the test geometry, specimen width, lamination history and failure location described in detail. Without this information, samples tested by different suppliers may not be comparable.

For a converter comparing films, five checks are critical: Choose the correct method, reproduce the bonding process, verify the setup of the tester, check the trace, and document the failure surfaces. The report checklist allows the purchasing and laboratory teams to consider the same questions. It provides no universal pass value for every fabric, foam or plastic assembly.

Updated October 2026. Standard editions were compared to the publishers’ public catalog; obtain the complete agreed method for laboratory execution.

What a peel strength result actually tells you

Peel adhesion testing defines the strength of an adhesive bond with a specific loading arrangement. The measured value includes the response of the adhesive and the materials being peeled. For a mechanical test result to be used as evidence of acceptable adhesion for a defined end use, the construction of laminate and test conditions must be described.

The 2023 review by Bartlett and colleagues differentiates reporting of strength in force/width from analysis of adhesion toughness. Backing deformation, material behavior and bond strength are load- and arrangement-specific. Therefore, a single result can’t isolate the strength of the adhesive from the rest of the assembly.

How to check adhesive strength?

Let’s review loading conditions first. Peel testing demonstrates progressive separation. On the other hand, lap shear testing loads an overlapping lap joint in a different manner. Other service qualification requirements may include testing for creep and/or environmental exposure. The customer should be asked to prioritize failures. A flexible adhesive that resists peeling can still require separate evidence for sustained shear loading.

Report-review mistake: approving a textile bond because the fabric tore. Substrate rupture locates the failure, but it may prevent measurement of separation along the adhesive interface. Record the rupture and compare it with the customer’s performance requirements.

“This test procedure does not provide design information.”

A test result of N/mm (or other similar unit of measure) is attributed to its construction. A 1.2 N/mm result is illustrative, and can’t by itself be used to demonstrate wash durability or to set an allowable service load. Procurement should request relevant environmental conditions and acceptance criteria before using the result to approve the product.

Choose the peel method for your laminate

Select a peel method that matches the flexibility of the two adherends and the customer specification. T-peel normally involves two flexible adherends. A flexible adherend bonded to a rigid substrate calls for a different arrangement. Report the test standard and the actual arrangement used, rather than “ASTM tested.”

What is the ASTM standard for peel testing?

ASTM D1876-08(2023) covers relative peel resistance using a T-type specimen. ASTM D903-98(2025) covers comparative peel or stripping with defined specimen preparation and test conditions. Their public scopes do not supply a complete laboratory procedure or a universal acceptance threshold.

Use this selection matrix to determine the next available technical check. Its application groups are editorially oriented and aren’t intended to describe nine distinct standard methods.

ISO 8510-2:2006, confirmed in 2025, addresses 180° peeling of flexible-to-rigid assemblies. A purchasing specification requesting 90° peeling needs its own agreed method. A change from 90° to 180° changes the setup; converting both results to N/mm does not resolve that mismatch.

Prepare substrates and hot melt film for lamination

Prepare peel specimens with actual substrates and adhesive films and provide details on bonding processes. Identify and describe batches and surface condition, and measure and record thickness of the films. Note the condition of surfaces to be bonded and the application temperature, pressure and the time the assembly was held under pressure (dwell time). Record and describe the cooling and conditioning of the assembly. These details may help explain variations in the performance of the adhesive film.

Document the surface preparation and cleanliness of both substrates and the release liners used for the peel bond. Prepare separately identified routes for surface treatments on various surfaces. A release liner, or something else, may have contaminated the adhesive surface. Preserve the production direction of fabrics and identify which faces are bonded. A description such as “polyurethane film on polyester” leaves too many assembly details unresolved. Too many details are left to the imagination.

Teng Yang’s published TPU hot melt film grade table illustrates why a single press setting can’t represent every grade. It lists TB65 at 80–85°C bonding temperature, TB95 at 110–115°C, TB115 at 130–135°C and TB130 at 145–150°C. The listed dwell range is 10–30 s, with pressure of 1.5–3 kgf/cm². These are first party catalog conditions, not a matched peel-test dataset.

Cooling deserves its own field. Longhenry, Love, and Murthy’s PCTFE/glass study showed that cooling rate was related to crystallinity, ductility, and peel results. Its findings do not establish a preferred cooling rate for every TPU or polyamide film. Record the actual cooling path, as equal waiting times don’t always mean equal material history.

The catalog bonding ranges for TB65 and TB130 are 80-85°C and 145-150°C, respectively. An experiment at one arbitrary press temperature can disadvantage a grade before testing begins. Come to an agreement on whether the trial is to evaluate one fixed production process or each grade’s process window, and label the comparison accordingly.

Set up the tester and check the force trace

Upon agreement of the test method for a controlled peel, secure the peel arms, and check alignment before collecting the result. Confirm force measurement, specimen dimensions, movement of the fixture, and how the results are recorded. Save the force trace because an average force, alone, can conceal a number of things including slip, an initial peak or a change in the failure behavior of the specimen.

Vertical T-peel requires attention to the un-peeled section. Padhye and colleagues’ study reported that, in thin and flexible laminates, asymmetries and additional forces may be introduced as a result of gravity. Document support and alignment. Their research fixture isn’t a mandatory requirement for all peel standards.

Check before rerunning: A jagged trace isn’t sufficient proof of uncontrolled formulation. If movement occurred at a grip, flag the run under the agreed to validity rules. Quietly removing an inconvenient trace affects comparison of suppliers’ specimens.

For a nominal 25 mm strip in an illustrative trial, verify the actual prepared width and save the trace under that specimen’s identifier. Slip and angle drift should be resolved prior to releasing a mean force. A clean looking spreadsheet can’t correct an uncontrolled test setup.

Calculate and report peel strength without hiding the trace

Report the specimen width and evaluation interval along with the results. Keep the initial peak separate when the method excludes it, and retain individual specimen values instead of publishing only a batch average.

The public ASTM D1876 abstract describes evaluation following the initial peak and a record of load against movement or peeled distance. This establishes the significance of the trace; the complete method supplies the procedural details. Do not use an averaging window just because it produces the highest value.

Worked example: suppose the valid interval gives an average force of 30 N and the strip width is 25 mm. Force per width = 30 N ÷ 25 mm = 1.2 N/mm, equivalent to 30 N per 25 mm width. If the same trace starts with a 45 N peak, that peak divided by width is 1.8 N/mm; it must not silently replace the interval average.

A second illustrative specimen averages 24 N over a 20 mm width: 24 N ÷ 20 mm = 1.2 N/mm. Matching units makes the arithmetic readable. Different widths can still affect the experiment, so normalized numbers alone don’t prove that the two specimen preparations were equivalent.

A 30 N mean on a 25 mm specimen yields 1.2 N/mm in the stated arithmetic example. A 45 N startup peak yields a different statistic, 1.8 N/mm. Before accepting a higher number from a supplier, request the force trace, and clarify which statistic the purchasing limit describes.

Read the failure surfaces before changing the adhesive

Observe both separated surfaces, and note where failure occurred. Interfacial separation, failure in the adhesive layer, and rupture of the substrate answer different questions. Use photographs alongside the force trace. In the case of delamination, a peel result can’t diagnose surface contamination or insufficient lamination or an unsuitable polymer.

ISO 10365:2022 standardizes designation of main failure patterns for adhesive bonds. Its public abstract does not provide all of the classification diagrams. Where the path changes during peeling, retain that observation rather than assigning the entire specimen to a convenient label.

Inspect surface preparation and the process record in addition to wetting. Adhesive remaining on both sides calls for closer inspection of cohesion and the failure path. Torn foam or fabric is an indication of failure of the adherend. Each observation leads to further inspection; “increase temperature” or “use a stronger adhesive” isn’t automatically the answer.

The choice of adhesive system is material dependent. As the Bartlett review explains, a fracture can occur at an interface or within adhesive or adherend material. A higher force accompanied by a different failure location may reflect a changed limiting part of the laminate. Qualify the assembly the customer will use.

Can you compare T-peel, 90-degree and 180-degree results?

Compare results directly only after checking whether the methods and assemblies are sufficiently matched for the question being asked. T-peel, 90° and 180° configurations load and deform specimens differently. Geometry and backing properties, as well as preparation, the environment and the speed of the test cannot be neglected.

The 2023 peel-test review mentions dependence on geometry and material deformation. In practice, we’ll ask for a matched retest if two suppliers use different arrangements. A validated mechanics analysis may support a narrower comparison, but a purchasing spreadsheet should not assume a universal angle multiplier.

Let’s say one supplier reports 1.2 N/mm from T-peel and the other reports 1.8 N/mm from 180° peeling. Those illustrative numbers do not establish a 50% improvement in the same bond. First match the pair of substrates, adhesive thickness, lamination process and evaluation method. Then, compare the new sample results and their scatter.

A 90° result and a 180° result can both be valid within their stated methods. When a buying decision entails ranking, agreement on a common test is prior to the comparison of N/mm values. A supplier can’t provide the method and preparation record? Label the report, “not yet comparable.”

Use a Peel Report Passport before approving a supplier

A Peel Report Passport is an editorial checklist connecting a peel value to its specimen, process, method and observed failure. Use this tool to identify missing information before performing a comparison. Completing fields does not assure equivalence, predict service life or replace the customer’s acceptance specification. The limits of the ISO 11339 test scope still apply.

Use the materials and methods section of the laboratory request to capture this report matrix. Entries describe what to record, with units where relevant; blank values must come from the agreed test, not from a generic online recommendation.

When negotiating a peel limit for the automotive interior laminate, discuss the exposure and loading conditions to determine the limits of the application. A similar case may be an assessment of a flexible packaging trial; however, the limits of application may vary for each case. The same applies to the assessment of a woodworking joint. Neither an initial tack, nor an unspecified and vague claim of strong adhesion closes the application gap for either case.

When discussing hot melt adhesive film options with Teng Yang, provide your substrate pair and available report. Include constraints and end-use exposure. This gives the supplier a basis to recommend a grade and a trial, without them thinking you’ve already qualified an untested combination.

Frequently asked questions

The interpretation of the peel test overlaps with surface science and production considerations. The responses below show what a report will or won’t show. Use the grade document and agreed laboratory method to set conditions; don’t bring in an unrelated adhesive’s recipe to a new laminate.

Is cohesive failure the same as adhesive failure?

No. Cohesive failure happens within a material; interfacial adhesive failure happens between bonded materials.

How to interpret the separated faces

Inspect both faces before naming the failure. Material remaining on both sides may suggest a path within the adhesive, but a thin coating or torn substrate can complicate visual interpretation. Ask the laboratory to photograph the surfaces and document mixed patterns. The name describes the failure location; it does not establish the root cause or prove that the product meets its acceptance limit. See the ISO 10365 failure-pattern scope.

Does surface roughness increase adhesion?

Roughness can’t determine whether a particular adhesive will provide better interfacial strength.

What to check besides texture

Distinguish available surface area from actual contact area between the adhesive and substrate. The molten adhesive must wet the surface under the bonding conditions. Cleanliness, surface treatment and melt viscosity belong in the investigation. Measurements such as contact angle, surface tension or surface energy help characterize wettability; they don’t replace a peel test on the finished laminate. Keep preparation consistent when comparing textures.

Should every grade use the same coating settings for a fair comparison?

When examining just one production process, use the same settings; when comparing each grade’s workable process, use the settings justified by grade.

How to define a fair trial

State which question the trial answers before preparing samples. One production line may have a strict application-temperature limit, so every candidate must work within it. A material-development comparison can instead use each grade’s documented process settings. Record any changes and preserve the other controlled variables. A pressure-sensitive adhesive, often called a PSA, also needs its own preparation logic; initial contact behavior is different from thermal activation of a non-pressure-sensitive film.

How long should a laminate rest before peel testing?

Use the conditioning time and environment specified by the agreed method and material instructions.

What to put in the report

Record elapsed time, temperature and relevant humidity. There’s no single waiting period established here for all film chemistries and substrates. Keep cooling history separate from the time between bonding and testing.

What should we send Tengyang for adhesive selection?

Provide the pair of materials, the desired thickness of the films, the present bonding sequence and acceptability criteria. Provide reports of both successful and failed samples, if available, and photos and/or force curves.

Information that makes a grade discussion more useful

Identify the polymer family and any coating on each substrate surface. A trade description alone may conceal an acrylic coating or a copolymer construction. Add the press limits, usable contact area, wash or heat exposure requirements and the existing failure pattern. A formulation document may identify thermal properties such as glass transition temperature, but those descriptors don’t supply an acceptance result. Ask which properties matter to the proposed trial instead of treating a chemistry label as evidence of peel performance. The supplier needs the intended assembly and process to decide which material information matters. For the broader material-choice question, our film, powder, web and pellet comparison explains the delivery formats to discuss before trial preparation.