Testing standard
Standard Test Method for Peel Adhesion of Pressure-Sensitive Label Stocks at a 90° Angle
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM D6252 measures the peel adhesion of pressure-sensitive label stocks at a 90° angle, normally from a stainless steel panel at about 300 mm/min. It is a quality-assurance tool for assessing uniformity within a roll or sheet, between rolls, and between production lots.
A strip of label stock about 25 mm wide is applied to a prepared panel — stainless steel unless another surface of interest is specified — under a defined roller pressure, and left for a specified dwell. The panel is then mounted on a platform that travels horizontally while the free tail of the label is pulled vertically at about 300 mm/min, so that the peel angle stays at 90° throughout. The force is averaged over the steady portion of the peel, excluding the initiation peak, and divided by the strip width.
How firmly the label holds, as a comparative quality figure. The method is explicit that its purpose is quality assurance — assessing whether adhesion is uniform within a sheet or roll, between rolls, and between production lots — rather than predicting field performance. That distinction is worth holding onto, because substrate, dwell, temperature and application pressure all move the number substantially, and all of them differ between the laboratory and a filling line. What the test does well is detect a change in a product that used to be consistent.
Ninety degrees only stays ninety degrees if the panel moves as the strip comes off. That is what the fixture is for.
This is a comparative quality tool, not a prediction of whether a label will stay on a product. Substrate, dwell, temperature and application pressure all move the answer, and all of them differ in the field.
Average force over the peel, divided by the strip width
Force per unit width. The averaging length and the start-up region are treated as in any peel test — the initiation peak is not the result.
Peel force rises with time under contact
A pressure-sensitive adhesive flows into the surface after application. Twenty minutes and twenty-four hours give materially different figures on the same stock.
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 properly, and a sliding 90° platform. Label peel forces are commonly a few newtons or less, so the load cell is chosen for the force rather than the frame — a cell sized for the machine works far below the range its accuracy class covers and produces a plausible trace with no traceable accuracy, which is the commonest measurement error in pressure-sensitive testing. The platform is not optional: without it the angle opens as the peel advances and the value becomes an average over a drifting geometry.
Peeling against a fixed panel, so 90° is 90° only at the start. Omitting the dwell time, which makes the figure incomparable. Quoting a peel value without its angle, when a 90° and a 180° result are different numbers for the same label with no conversion between them. Reading adhesion to steel as adhesion to the customer's actual surface. And reporting a force without the failure mode, when adhesive transferred onto the panel is a complaint waiting to happen even at a perfectly acceptable force. Panel preparation belongs here too: stainless steel is a reference surface only while it is clean, and a panel carrying residue from previous strips will read low in a way that looks like a change in the label stock rather than in the laboratory.
| ASTM D6252 | ASTM D3330 | |
|---|---|---|
| Written for | Pressure-sensitive label stocks | Pressure-sensitive tapes |
| Angle | 90°, platform-held | 180° and other angles |
| Fixture | Sliding panel required | Strip folds back on itself |
| Cite | Where the specification names it | Where the specification names it |
Peel force depends on angle, so a 90° figure and a 180° figure are different numbers for the same label and neither converts to the other. The angle belongs with the value, always.
It is the ASTM 90° peel adhesion test for pressure-sensitive label stocks. A strip about 25 mm wide is applied to a panel — stainless steel by default — left for a specified dwell, then peeled at roughly 300 mm/min while the angle is held at 90°. It is a quality-assurance method for assessing uniformity within a sheet or roll, between rolls, and between production lots.
To keep the angle at 90°. If the panel is fixed and the strip is simply pulled upward, the peel front travels along the panel while the grip stays put, so the angle opens progressively as the test runs. Since peel force depends strongly on angle, the result then becomes an average over a geometry that changed during the measurement. A platform that travels horizontally as the strip comes off keeps the angle where the method says it is.
Because a pressure-sensitive adhesive is not finished when it is applied. It continues to flow into the microscopic roughness of the surface, so the contact area grows with time and the peel force rises with it. Twenty minutes and twenty-four hours give materially different figures on the same stock, which is why the dwell is specified and why an unreported dwell makes a result incomparable with anything.
Not directly. Stainless steel is a clean, hard, high-energy reference surface chosen because it is reproducible, not because it resembles a real label application. Corrugated board, polyethylene bottles, chilled glass and powder-coated surfaces all behave differently. The method permits other surfaces of interest for exactly this reason, and whichever was used has to be reported.
Because the modes have different consequences. A label that lifts cleanly is a peel result. Adhesive left behind on the panel is cohesive failure or transfer, which means residue on the customer's product — a complaint even when the recorded force was perfectly acceptable. A torn face stock means the label is weaker than its own adhesive. The force alone cannot distinguish these.
A small one. Label peel forces are commonly a few newtons or less, so a cell sized for the frame will be working far below the range its accuracy class covers and will produce a plausible-looking trace with no traceable accuracy. This is the single most common measurement error in pressure-sensitive testing.
No. Peel force depends on angle because part of the measured force goes into bending the face stock rather than breaking the bond, and that share changes with the geometry. A 90° value and a 180° value are different numbers for the same label with no conversion between them, which is why the angle belongs alongside the figure in any specification or data sheet.
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 — label peel forces are commonly a few newtons or less | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | Verified at the actual peel force, which is a small fraction of most frames' capacity | ISO 7500-1 Class 0.5, verified to ASTM E4, DIN 51221 and BS 1610 |
| Gripping | A 90° peel fixture: the panel travels horizontally as the strip is pulled vertically, so the angle stays at 90° | Our peel and adhesion fixtures, 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.
