Testing standard
ISO 813
Rubber, vulcanized or thermoplastic — Determination of adhesion to a rigid substrate — 90 degree peel method
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 813 measures the strength of a bond between vulcanised rubber and a rigid substrate by peeling a rubber strip from a single plate at a constant 90°. The angle is held by translating the plate as the strip is drawn away — without that, the geometry changes as the test proceeds and the force follows it. Where the failure runs matters as much as the number.
At a glance
- Test type
- Peel & adhesion — a bonded joint is pulled apart
- Published by
- ISO
- Edition
- ISO 813:2019
- Material
- Rubber, elastomers & foams
- Runs on
- Series 7200 and Series 9000
What the test does
A strip of rubber is vulcanised directly onto a single rigid plate — most often metal, prepared exactly as production prepares it — so the bond forms as the rubber cures. The plate is mounted on a sliding platform and the free end of the rubber strip is clamped in the upper grip. As the crosshead rises at about 50 mm/min, the platform translates so that the strip is always being peeled away at ninety degrees to the plate. Force is recorded throughout, the run-in transient discarded, and the remainder averaged over a steady length and divided by the bonded width. The plate is then examined to see how much rubber stayed on it.
What it measures, and why it matters
The result is a peel strength in force per unit width, together with the proportion of the bonded area still covered in rubber. Bonded rubber-to-metal parts carry load in almost every machine that has to isolate vibration or absorb shock — engine and gearbox mounts, suspension bushes, machinery pads, printing and conveyor rollers, rubber-lined pipework and marine fenders. In all of them the bond is the element most likely to fail and the least likely to be inspected. What this test really asks is whether the joint is stronger than the rubber it joins; when it is, the rubber tears and leaves a layer behind, and there is nothing further to gain at the interface.
Specimen and the 90° arrangement
The defining feature is the constant angle. Everything in the fixture exists to keep it constant.
- Construction
- A rubber strip vulcanised to one rigid plateA single plate, unlike ISO 814 which sandwiches the rubber between two.
- Bonded width
- 25 mm typical
- Peel angle
- 90°, held constant throughoutThe plate must translate as the strip is drawn up. A fixed plate lets the angle open continuously and the force falls for a purely geometric reason.
- Substrate preparation
- Exactly as production does itBlasting, degreasing, primer and flash-off are the largest levers in the result.
- Vulcanisation
- Bond formed during cure
- Record the primer
- Type and flash-off timeDakUnrecoverable afterwards, and the first thing anyone investigating a failure asks for.
A peel test without a sliding platform is not this method. It will produce a smooth, plausible, falling trace — and the fall is the angle opening, not the bond weakening.
Test speed
- Rate
- Commonly 50 mm/min
- Averaging
- Steady region only, run-in discarded
- Check the angle mid-run
- Not only at the startDakA platform that binds part-way through changes the geometry silently.
Calculations
Peel strength = average peel force / bonded width
- average peel force
- mean over the steady region, N
- bonded width
- mm
In N/mm or kN/m. A peel front has no area, so this is never a stress.
Percentage of the bonded area still covered in rubber
Reported with the force. Full retention means the compound failed before the bond, which is the design intent for a bonded part.
How the test runs
- 01Prepare the plate exactly as production does — blast, degrease, prime, flash off.
- 02Vulcanise the rubber strip to the plate in one operation.
- 03Trim to the bonded width and measure it.
- 04Condition in the standard laboratory atmosphere.
- 05Mount the plate on the sliding platform.
- 06Clamp the free end of the rubber strip in the upper grip.
- 07Check the peel angle is 90° before loading.
- 08Peel at 50 mm/min, recording force.
- 09Confirm the angle is still 90° part-way through.
- 10Discard the run-in and average over a steady length.
- 11Examine the plate and estimate rubber retention.
What the report has to contain
- Reference to ISO 813 and the edition
- Rubber compound and substrate material
- Surface preparation and primer, with flash-off time
- Vulcanisation schedule
- Bonded width
- Conditioning and test temperature
- Rate of separation
- Average peel force and peel strength per unit width
- Percentage rubber retention
- Number of specimens and the median
What the machine must be capable of
Modest force with accurate resolution at the low end — peel forces commonly run from fifty newtons to about a kilonewton and a half over a 25 mm width — and a crosshead holding 50 mm/min. The defining requirement is not force at all but the sliding platform that keeps the peel angle at ninety degrees as the bond opens. Without it the geometry changes continuously through the run. The frame also needs enough travel to peel a useful length after the run-in is discarded, and where elevated-temperature testing is specified, the plate and its rubber must reach temperature rather than merely be surrounded by hot air.
What goes wrong in practice
Running the test without a sliding platform is the characteristic error, and the reason it persists is that the result looks entirely reasonable: a smooth trace that declines steadily along the specimen, which reads as a bond weakening down its length. It is the peel angle opening, not the bond changing. A platform that binds part-way through does the same thing less obviously, which is why the angle is worth checking mid-run rather than only at the start. Beyond the fixture, inconsistent substrate preparation accounts for most disputed results, and reporting a force without the rubber retention loses the distinction between a bond that beat the compound and one that simply let go.
ISO 813 or ISO 814
| ISO 813 | ISO 814 | |
|---|---|---|
| Construction | Rubber on one rigid plate | Rubber between two rigid plates |
| Loading | 90° peel | Tension pulling the plates apart |
| Represents | A bonded facing or lining | A bonded sandwich mount |
| Result | Force per unit width | Force |
These describe different articles and are not substitutes. A lining peels; a sandwich mount is pulled apart. Choosing the geometry that matches the part is the point of having both.
Questions we are asked about this test
What is ISO 813?
It is the ISO method for the adhesion of vulcanised or thermoplastic rubber to a rigid substrate, measured by peeling a rubber strip from a single plate at a constant 90°. The result is a peel force per unit width, reported with the proportion of rubber left on the plate.
Why does the plate have to slide?
To hold the angle at 90°. If the plate is fixed, the peel angle opens continuously as the strip is drawn away, and the recorded force falls with it — smoothly and plausibly, which is what makes the error hard to spot. The falling trace looks like a bond weakening down the specimen and is nothing of the sort.
What is the difference between ISO 813 and ISO 814?
The article they describe. ISO 813 peels rubber off a single plate, which is what happens to a bonded lining or facing. ISO 814 pulls two plates apart with rubber vulcanised between them, which is what happens to a sandwich mount. Different geometries, different failures, not substitutes for one another.
How does it compare with ASTM D429?
ISO 813 corresponds closely to D429 Method B, the 90° peel from a single plate. D429 is a family carrying several other lettered methods as well, so a bare reference to D429 does not say which geometry was used, whereas ISO 813 is unambiguous.
Why is surface preparation the biggest variable?
Because the bond forms during vulcanisation onto whatever surface is presented. Grit blasting, degreasing, primer type and the flash-off time between coats all change how the rubber keys to the metal, and a bond that separates cleanly at the interface is usually reporting on that preparation rather than on the compound. It also cannot be reconstructed after the fact, which is why it is recorded.
What does full rubber retention mean?
That the compound tore before the bond did — the joint is stronger than the material it joins. That is the design intent for any bonded rubber part, and once it is achieved, raising the recorded force means changing the rubber rather than the bond.
Should I test hot?
If the part runs hot, yes. Rubber-to-metal bonds are generally weakest at elevated temperature, and mounts, bushes and rollers commonly work warm. Where the specification names a temperature, testing at ambient is not a conservative simplification but a different test, and the whole assembly has to reach temperature rather than merely sit in warm air.
Running ISO 813 on the Series 7200 and Series 9000
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 | Low to moderate — commonly 50 N to 1.5 kN over a 25 mm bonded 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 over the working range | ISO 7500-1 Class 0.5 — a class tighter than the method asks |
| Gripping | A 90° peel arrangement: the rigid plate translates as the rubber strip is drawn vertically, holding the angle constant | Our peel and adhesion fixtures, built to the specimen |
| Environment | 23 ± 2 °C standard laboratory atmosphere unless elevated temperature is specified | 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.