Testing standard
Rubber- or plastics-coated fabrics — Determination of coating adhesion
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 2411 determines how well a rubber or plastics coating holds to the fabric beneath it. A strip is prepared with the coating separated at one end, the two layers are pulled apart at a constant rate, and the mean force over the separation is reported per unit width.
Strips are cut in the warp and weft directions and conditioned. The coating is separated from the base fabric at one end to a consistent length, and where it cannot be lifted by hand an intermediate strip is bonded to it so that there is something to grip. The separated coating goes into one jaw and the base fabric into the other, and the two are pulled apart at a constant rate so the delamination advances progressively. The mean force over the steady portion — excluding the higher force needed to start it — is divided by the specimen width to give the coating adhesion.
Whether the coating stays on. This is the failure mode a tensile test cannot see, and it is independent of strength: a coated fabric can pass ISO 1421 comfortably and still delaminate in service, because the yarns carrying load and the bond holding the coating to them are separate things. A membrane whose coating lifts has failed as completely as one that tore. That is why coated fabric specifications carry both a tensile requirement and an adhesion requirement, and why neither can be inferred from the other.
The hardest part is beginning the peel, and how it is begun affects the whole test.
This is the failure mode a tensile test cannot see. A coated fabric can be perfectly strong in ISO 1421 and still delaminate in service, because strength and adhesion are independent properties.
Mean separation force divided by the specimen width
Force per unit width, commonly N/mm or per 50 mm of width. State which, since both conventions are in circulation.
Excluded from the mean
Beginning a separation costs more force than continuing one, and the excess depends on how the start was made.
Pneumatic vice action grips hold each arm of the T at a constant pressure through a long peel, which a screw grip does not — a peel test runs for hundreds of millimetres and a slipping grip corrupts the whole trace.
SpecificationsVery small forces measured well, and long travel. Coating adhesion commonly sits between a few newtons and a few tens of newtons per specimen width, so the load cell is chosen for that range rather than for the frame — an accuracy class applies only down to a stated fraction of capacity. Both the lifted coating and the base fabric are thin and easily damaged, so grip pressure has to hold them without cutting either, and it must hold for the whole length of the separation rather than only at the start.
Quoting adhesion without the width convention, when both newtons per millimetre and force per 50 mm are in circulation and they differ by a factor of fifty — a mistake that passes unnoticed into specifications. Reporting a substrate failure as an adhesion value, when what was actually overcome was the cohesion of the weave. Inconsistent starts, which move the mean. And losing the intermediate bond before the coating separates, which measures the wrong adhesive entirely.
| ISO 2411 | ISO 1421 | |
|---|---|---|
| Question | Does the coating stay on? | How strong is the fabric? |
| Failure mode | Delamination | Break |
| Predicts the other | No | No |
| Run together | Usually | Usually |
These are the two halves of specifying a coated fabric, and neither implies the other. A strong fabric whose coating peels is a failed product, and a well-bonded coating on a weak base is equally useless.
It is the ISO method for the coating adhesion of rubber- or plastics-coated fabrics — how firmly the coating holds to the textile beneath it. A strip is prepared with the coating separated at one end, the two layers are pulled apart at a constant rate, and the mean separation force over the steady part of the run is reported per unit width. The current edition is ISO 2411:2024, the fifth.
Because they are independent properties and both can fail a product. ISO 1421 asks how much load the fabric carries before it breaks; this asks whether the coating stays attached to it. A membrane or tarpaulin whose coating delaminates has failed just as completely as one that tore, and nothing in a tensile result gives any warning of it. The two are specified together for that reason.
The method provides for bonding an intermediate strip to the coating so that there is something to grip, and taking the peel through that bond. It has to be recorded in the report, because the result then depends on the bonded strip holding — if that bond fails first, the measurement is of the intermediate adhesive rather than of the coating, and the specimen is lost.
Because beginning a peel costs more force than continuing one, and the excess depends entirely on how the start was made — how far the coating was lifted, whether the lift was clean or ragged, whether any substrate came away with it. Including that region reports the specimen preparation. Running far enough to establish a steady trace and averaging only that portion removes it.
That the adhesion is higher than the cohesion of the base fabric itself — the bond is stronger than the weave. It is a legitimate finding and often a good one, but it is not a measurement of adhesion, because what was overcome was the fabric. It should be recorded as substrate failure rather than reported as an adhesion value, since a stronger coating bond would not change the number.
Because the coating meets a different surface in each direction. A woven base presents a different pattern of crimp, float length and yarn exposure along the warp than across it, so the mechanical key the coating forms differs, and the peel travels through a different geometry. Testing and reporting the two separately follows the same logic as it does for tensile strength.
Force per unit width — but two conventions are in circulation, newtons per millimetre and force per 50 mm of specimen width, and they differ by a factor of fifty. Stating which was used is not pedantry: an adhesion figure quoted without its width convention is a number that could be either, and the two are far enough apart that the mistake passes unnoticed in a specification.
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | Very low — coating adhesion is commonly a few newtons to a few tens of newtons per specimen width | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ISO 7500-1 Class 1 at the actual separation force | ISO 7500-1 Class 0.5 — a class tighter than the method asks |
| Gripping | Grips taking the separated coating in one jaw and the base fabric in the other | Wedge, vice-action, pneumatic and hydraulic grips, built to the specimen |
| Environment | 23 ± 2 °C standard laboratory atmosphere | 3009 series chambers, −150 °C to +400 °C — temperature only |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.
