Testing standard
Standard Test Method for Protrusion Puncture Resistance of Stretch Wrap Film
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM D5748 measures the protrusion puncture resistance of stretch wrap film: the film is clamped over a circular opening and a blunt probe is driven through it at a single slow speed, giving maximum force, force at break, penetration distance and energy to break. Energy is the property the test exists for, because puncture resistance is an energy-absorbing behaviour rather than a strength. The current edition is D5748-26.
A sheet of stretch wrap film is clamped around its edge over a circular opening, leaving a free circular area of film with no support behind it. A blunt, rounded probe is driven into the centre of that free area at a single, slow, standardised speed until the film ruptures. Force and probe travel are recorded throughout, and the area under the curve gives the energy the film absorbed before it failed. Held all round and pushed in the middle, the film is stretched in every direction at once — the biaxial state a protruding corner or carton edge puts a wrap into.
Four quantities: maximum force, force at break, the distance the probe travelled into the film, and the energy absorbed to break. The energy is the one that matters. Puncture resistance is an energy-absorbing property, and a film can be strong and still poor at it — a stiff film that reaches a high peak force and then rips at very little penetration absorbs less than a compliant one that stretches a long way at a lower force and holds. That distinction is invisible in a tensile test and it is what decides whether a pallet load survives a fork tine, a strapping corner or a carton edge in transit. Because stretch wrap is used pre-stretched and biaxially loaded, this test reproduces the service stress state far more closely than a uniaxial pull, and buyers use it to rank films and to police incoming lots.
Thin, tacky and easily distorted. The clamping is the preparation, and film drawn in at the rim is the commonest way the result goes wrong.
If the film draws in at the clamp during the test, the extra travel is counted as penetration and the energy is overstated. Nothing in the trace shows it happened.
The area under the force against penetration curve, to rupture
The headline result. Because it is an integral, a coarse force channel or a poorly resolved position channel corrupts it even when the peak force looks correct.
The peak of the trace, and the force at the moment of rupture
They are not always the same point. A film that necks locally can peak before it tears.
Probe travel from first contact to rupture
The measure of how far the film stretched before it gave up, and the reason a compliant film can outperform a stronger one.
A low-range cell. A stretch film a few tens of microns thick develops small forces over a long probe travel, and the result is an integral of both — a cell chosen for the frame rather than the specimen throws away the resolution the energy calculation depends on.
SpecificationsLow force, high resolution and a long, smooth stroke. Forces are small — a stretch film is a few tens of microns thick — while the probe may travel a long way before the film breaks, so the frame needs travel and a load cell chosen for the specimen rather than the frame. The result is an integral of force against displacement, so both channels matter equally: a coarse force reading or a poorly resolved position channel corrupts the energy even when the peak force looks right. The fixture is a ring clamp with a 102 mm (4 in.) opening and a 19 mm (0.75 in.) diameter pear-shaped, fluoropolymer-coated probe, driven at 250 mm/min. Data has to be captured fast enough that the rupture is not smoothed away, and the force channel has to be verified at the small load this test actually works at rather than at the capacity of the frame.
Film drawing in at the clamp, which is the dominant error and looks like a tougher film. A probe head that is scratched, contaminated or has lost its low-friction surface, which changes the friction against the film and therefore the whole curve. Testing a two-sided film the wrong way up. Reporting peak force alone, when the energy is the property the test was written to obtain. And comparing the result against a different puncture method: the probe, the opening and the speed all differ, and none of the numbers transfer.
| ASTM D5748 | ASTM F1306 | ASTM D882 | |
|---|---|---|---|
| Material | Stretch wrap film | Flexible barrier films and laminates | Thin plastic sheeting and film |
| Loading | Blunt probe through clamped film | Probe through clamped film, slow rate | Uniaxial tensile strip |
| Stress state | Biaxial | Biaxial | Uniaxial |
| Headline result | Energy to break | Penetration resistance and energy | Strength, elongation and modulus |
The probe, the clamp opening and the speed differ between puncture methods, so the numbers do not transfer even though the arrangement looks identical. Reading D882 alongside this test is what separates strength from toughness: a film can be strong in tension and poor at absorbing a protrusion.
It is the ASTM method for the protrusion puncture resistance of stretch wrap film. The film is clamped over a circular opening and a blunt probe is driven into the centre at a single slow speed until it ruptures, and maximum force, force at break, penetration distance and energy to break are reported. The current edition is D5748-26.
Because puncture resistance is an energy-absorbing property, not a strength. A stiff film can reach a high peak force and then rip at very little penetration, absorbing less than a compliant film that stretches a long way at a lower force and holds. Only the energy captures that, and it is the difference between a wrap that survives a fork tine and one that does not.
A 19 mm (0.75 in.) diameter pear-shaped probe with a fluoropolymer-coated tip, driven through film clamped over a 102 mm (4 in.) diameter opening at 250 mm/min. The probe is deliberately blunt and low-friction: the test represents a protrusion pressing out against a wrap, not a sharp object cutting it.
Because clamping the edge and pushing the middle stretches the film in every direction at once. That biaxial state is what a pallet corner, a strapping edge or a protruding carton actually imposes on a wrap in service, and a uniaxial tensile pull does not reproduce it. The scope says as much: the stress imparted is representative of the type encountered in end-use.
On a two-sided film, yes. Stretch films are commonly made with cling on one face and slip on the other, and the two surfaces behave differently against the probe and against the clamp. They should be treated as separate specimens, tested consistently, and the orientation recorded in the report.
No. The probe diameter, the probe shape, the clamp opening and the test speed all differ between puncture methods, and each combination imposes a different deformation on the film. ASTM F1306 uses a similar arrangement on flexible barrier films and laminates, but its numbers are its own. Compare films within one method, never across methods.
A frame with fine force resolution and a long, smooth stroke. Forces are small because the film is thin, while the probe may travel a long way before rupture, so the load cell is chosen for the specimen rather than the frame. Since the result is an integral of force against displacement, the position channel matters as much as the force channel.
Film drawing in at the clamp. Any slip at the rim adds travel that is not penetration, which inflates both the penetration distance and the energy, and makes a film look tougher than it is. After that: a probe whose low-friction coating has been scratched or contaminated, which changes the friction against the film and therefore the whole curve.
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. Stretch film is a few tens of microns thick, so forces are small while probe travel is long. The load cell is chosen for the specimen rather than the frame, because the headline result is an integral of the force and position channels together. | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | n/a — Practices E4 is NOT among this method's referenced documents, which are Practice D618 and Terminology D996, so no E4 requirement is attributed to it | ISO 7500-1 Class 0.5, verified to ASTM E4, DIN 51221 and BS 1610 |
| Gripping | Ring clamp with a 102 mm (4 in.) diameter opening and a 19 mm (0.75 in.) diameter pear-shaped, fluoropolymer-coated probe | Our compression anvils, built to the specimen |
| Environment | Condition and test in the standard laboratory atmosphere for plastics; Practice D618 is referenced | 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.
