Standard 25 mm
Pneumatic Vice Action Grip
Constant air pressure across the full jaw face — the arrangement that holds a film without cutting it at the clamp line, and identical on every specimen.
SpecificationsTesting standard
ASTM D882
Standard Test Method for Tensile Properties of Thin Plastic Sheeting
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM D882 is the tensile test for plastic film and thin sheeting up to 1.0 mm thick. A plain parallel-sided strip — no dumbbell waist — is pulled apart at a speed set by its expected elongation. It reports tensile strength, elongation at break, modulus, tensile energy to break and breaking factor, the force-per-width figure used where thickness cannot be gauged reliably.
At a glance
- Test type
- Tensile — the specimen is pulled apart
- Published by
- ASTM
- Edition
- D882-26
- Material
- Plastics, polymers & films
- Runs on
- Series 7200 and Series 9000
What the test does
A rectangular strip cut from film or thin sheet is clamped at both ends at a set grip separation. The crosshead moves at a constant rate and pulls the strip along its length until it breaks, while force and crosshead travel are recorded continuously. There is no narrow waist and no dumbbell — the specimen is a plain parallel-sided strip, so it may break anywhere along the free length.
What it measures, and why it matters
The method reports tensile strength, elongation at break, modulus of elasticity, tensile energy to break and breaking factor. Strength and elongation are the routine lot-release pair for packaging film — a drop in elongation flags degraded resin or a drift in orientation. Modulus feeds stiffness and web-handling calculations. Breaking factor, force divided by width, is used where thickness cannot be gauged reliably. Tensile energy to break, the area under the curve, ranks toughness between grades that share a similar peak load.
Strip, width and grip separation
There is no waisted section here, so the specimen can break anywhere along its free length — and the geometry rules exist to make sure it breaks for the right reason.
- Maximum thickness
- 1.0 mmAbove that the method does not apply and ASTM D638 takes over.
- Width-to-thickness ratio
- At least 8 : 1What keeps an edge flaw from dominating the break rather than the material.
- Common width
- 25.4 mmPractice
- Grip separation below 20 % elongation
- 125 mm
- Grip separation, 20 to 100 %
- 100 mm
- Grip separation above 100 %
- 50 mm
- Grip separation for modulus
- 250 mmReduced to 100 mm where 250 mm is impracticable. Modulus is run as a separate test, not read off the strength run.
- Conditioning
- At least 40 h, 23 °C and 50 % RHASTM D618 Procedure A, testing in the same atmosphere.
- Discard and replace
- Any break at the jaw line or an edge nick
- Cut with a sharp blade, every time
- Clean parallel edgesDakFilm is edge-sensitive and there is no waist to move the failure away from a nick. A blunt cutter produces a low result that looks like a material problem.
Test speed
The speed is chosen from the expected elongation, and it moves with the grip separation — so speed and separation are picked together rather than independently.
- Below 20 % elongation
- 12.5 mm/min at 125 mm separationAn initial strain rate of 0.1 min⁻¹.
- 20 to 100 % elongation
- 50 mm/min at 100 mm separation0.5 min⁻¹.
- Above 100 % elongation
- 500 mm/min at 50 mm separation10.0 min⁻¹.
- Rate tolerance
- Within 5 % of the set valueSo the frame needs genuine speed control at 500 mm/min under load, not a nominal setting.
- Estimate elongation first
- On a trial specimenDakThe speed depends on the answer, so the first specimen of an unfamiliar film is spent finding out which band it falls in.
Calculations
Tensile strengthTS
TS = F_max / (w × t)
- F_max
- maximum force, N
- w
- specimen width, mm
- t
- average thickness, mm
Breaking factorBF
BF = F_max / w
- w
- specimen width, mm
Force per unit width, reported INSTEAD of tensile strength where thickness cannot be gauged reliably — thin gauge-variable film, coated webs, laminates. It avoids dividing by a number nobody trusts.
Elongation at breakE
E = (extension / initial grip separation) × 100
- initial grip separation
- the reference length — 125, 100 or 50 mm as selected
Grip separation IS the reference length in this method, which is why the separation is a specified value rather than whatever the operator set.
Tensile energy to breakTEB
TEB = area under the force–extension curve / specimen volume
Ranks toughness between grades whose peak loads are similar — the number that separates a film that tears from one that stretches.
How the test runs
- 01Condition the film at least 40 hours at 23 °C and 50 % RH, and test in that atmosphere.
- 02Cut strips with a sharp blade, edges clean and parallel, width at least eight times the thickness.
- 03Measure thickness at several points along each strip and average it.
- 04Estimate elongation at break on a trial specimen if the film is unfamiliar.
- 05Set the grip separation for that elongation band — 125, 100 or 50 mm.
- 06Set the corresponding speed: 12.5, 50 or 500 mm/min.
- 07Clamp the strip square, with no slack and no pre-tension, using faces that will not cut the film.
- 08Run to break, recording force against extension.
- 09Discard anything that broke at the jaw line or at a visible nick, and replace it.
- 10Run modulus separately at 250 mm grip separation.
- 11Report breaking factor rather than tensile strength where thickness could not be gauged reliably.
Grip design matters more here than almost anywhere. Jaw faces that bite will cut a film at the clamp line, and faces that do not bite let it pull out — and both failures produce a curve that looks like a real test.
Watch the test
Grips and fixtures for this method
HJ-42
Light Duty Pneumatic Grip
Light duty closure for the lowest forces, where a heavier grip would crush a delicate web before the test began.
SpecificationsWhat the report has to contain
- Reference to ASTM D882 and the edition
- Complete film identification, including any orientation or coating
- Direction tested relative to machine and transverse direction
- Specimen width and average thickness, and how thickness was measured
- Initial grip separation, which is the reference length
- Rate of grip separation
- Conditioning, and the atmosphere at test
- Tensile strength, or breaking factor where thickness was not reliably gaugeable
- Elongation at break
- Modulus, with the separation it was run at
- Tensile energy to break where required
- Number of specimens, mean and standard deviation, and any specimen discarded
What the machine must be capable of
Loads are low. A 25 mm strip of packaging polyethylene breaks well under 100 N, so a 500 N to 1 kN cell on a bench frame covers most of this work and resolution at the bottom of the scale matters more than capacity. The widest, thickest specimen the method admits — 25.4 mm at the full 1.0 mm in a strong oriented polyester — would demand several kN, so capacity is chosen against the material rather than against the method. Force indication must be verified to ASTM E4.
Speed is set by expected elongation, not by preference: an initial strain rate of 0.1 min⁻¹ at 125 mm separation (12.5 mm/min) below 20 % elongation, 0.5 min⁻¹ at 100 mm (50 mm/min) from 20 to 100 %, and 10.0 min⁻¹ at 50 mm (500 mm/min) above 100 %. The rate must hold within 5 % of the set value, so the frame needs genuine speed control at 500 mm/min under load. Modulus is run separately at 250 mm separation.
No extensometer is required — strain comes from grip separation. Polyolefin film routinely runs past 500 % though, so a high-elongation or non-contact device gives a cleaner total elongation than crosshead travel does.
Grips must minimise slippage and spread clamping stress evenly. Pneumatic vice-action or wedge grips with flat rubber faces suit fragile specimens, line-contact faces suit slippery ones, and roller grips — the strip wrapped round a rubber-faced drum against a compression bar — suit thin film specifically. Faces must be wider than the strip. Serrated steel faces are wrong here: they nick the film and start the failure at the jaw line.
What goes wrong in practice
Jaw-line tears are the dominant invalid result — the film fails where the faces bite instead of in the free length, so the number is a grip artefact. Slippage is the other half of the same problem: the strip creeps out under load, extension reads long and modulus reads low. An edge nick from a blunt cutter initiates the break early and depresses strength by a wide margin. Thickness variance across a web is the quiet one — stress is calculated from a measured thickness, so a gauge taken at one point misprices the whole specimen.
Where D882 takes over from D638
| ASTM D882 | ASTM D638 | ISO 527-3 | |
|---|---|---|---|
| Applies to | Film and sheet up to 1.0 mm | Above 1.0 mm | Films and sheets |
| Specimen | Plain parallel strip | Waisted dumbbell | Plain strip |
| Reference length | Grip separation | Marked gauge length | 50 mm gauge |
| Speed basis | Set by expected elongation | Tabulated by specimen type | Nominal speed series |
| Distinctive output | Breaking factor, N/mm width | Tensile modulus | Tensile modulus |
The 1.0 mm boundary is not advisory. Gripping thin film in a D638 dumbbell geometry produces tab failures rather than data, and the waist that helps a rigid plastic simply becomes another place for a thin web to fail.
Questions we are asked about this test
What is ASTM D882?
It is the ASTM tensile test for thin plastic sheeting and film, up to 1.0 mm thick. A plain parallel-sided strip is pulled apart until it breaks, and the method reports tensile strength, elongation at break, modulus, tensile energy to break and breaking factor.
When do I use D882 instead of D638?
At 1.0 mm thickness. Below it, D882 applies; above it, D638. The boundary is not a formality — a thin film clamped in a D638 dumbbell geometry tends to fail at the tab rather than in the waist, so the test measures the grip. D882 uses a plain strip and a specified grip separation instead.
What is breaking factor and when should I report it?
It is the maximum force divided by the specimen width, in newtons per millimetre, and it is reported instead of tensile strength wherever thickness cannot be gauged reliably — thin gauge-variable film, coated webs, laminates. It avoids dividing a good force measurement by a thickness nobody trusts, which is how an apparently precise strength figure ends up carrying someone else's measurement error.
What speed does ASTM D882 use?
It depends on the film's expected elongation, and it moves with the grip separation. Below 20 % elongation the test runs at 12.5 mm/min with 125 mm separation; from 20 to 100 % at 50 mm/min with 100 mm; above 100 % at 500 mm/min with 50 mm. The rate must hold within 5 % of the set value, so a frame needs real speed control at 500 mm/min under load.
Why is grip separation specified rather than left to the operator?
Because in this method the grip separation IS the reference length that elongation is calculated from. There is no marked gauge on a plain strip and often no extensometer, so the distance between the jaws at the start is what the strain is referred to. Setting it arbitrarily makes the elongation figure meaningless.
What load cell does ASTM D882 need?
A small one. A 25 mm strip of packaging polyethylene breaks well under 100 N, so a 500 N to 1 kN cell on a bench frame covers most of this work, and resolution at the bottom of the scale matters far more than capacity. The heaviest case the method admits — 25.4 mm at the full 1.0 mm in a strong oriented polyester — would demand several kN, so capacity follows the material rather than the method.
Why did my film break at the grip?
Jaw faces that bite too hard cut the film at the clamp line; faces that do not bite let it pull out. Both are common with film and both produce a curve that looks like a genuine test, which is why the specimen has to be inspected after every break. A break at the jaw line is invalid under the method and must be replaced rather than averaged in.
Do I need to test in more than one direction?
For any oriented film, yes. Blown and cast films are anisotropic, so machine-direction and transverse-direction results differ, sometimes by a large factor. The direction tested has to be reported, and a single figure quoted without it does not describe the film.
Running ASTM D882 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 | Thin sheeting parts at low load — a 25 mm wide strip of packaging polyethylene breaks well under 100 N — so the useful range is a load cell of 500 N to 1 kN on a single- or twin-column bench frame, and force resolution at the bottom of the scale matters far more than capacity. The widest, thickest specimen the method admits, 25.4 mm at the full 1.0 mm thickness in a strong oriented polyester, would demand several kN, so capacity is chosen against the material rather than the method. | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ASTM E4 | Verified to ASTM E4, and to ISO 7500-1 Class 0.5 |
| Gripping | Pneumatic vice or wedge grips with flat rubber or line-contact faces, or roller grips, at a set grip separation | Our vice-action grips or self-tightening eccentric roller grips, built to the specimen |
| Environment | Condition at least 40 h at 23 °C / 50 % RH per ASTM D618 Procedure A and test in the same 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.