Standard 25 mm
Pneumatic Vice Action Grip
Pneumatic vice action grips clamp the full specimen width at a constant, even pressure — which is what stops one side slipping or tearing before the other.
SpecificationsTesting standard
ISO 6383-1
Plastics — Film and sheeting — Determination of tear resistance — Part 1: Trouser tear method
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 6383-1 determines the tear resistance of plastic film or sheet less than 1 mm thick using trouser-shaped specimens. The average force to tear the specimen along its length is divided by the thickness and reported in newtons per millimetre.
At a glance
- Test type
- Tear — a cut or nick is forced to grow
- Published by
- ISO
- Edition
- ISO 6383-1:2015
- Material
- Plastics, polymers & films
- Runs on
- Series 7200 and Series 9000
What the test does
A rectangular specimen of film or sheet less than 1 mm thick is pre-treated and conditioned, its thickness measured at several points along the intended tear path, and a longitudinal slit cut over half its length to form two trouser legs. One leg is gripped in each jaw and they are separated at the specified speed under defined temperature and humidity. The average force over the tearing portion of the trace is divided by the specimen thickness, giving a tear resistance in newtons per millimetre.
What it measures, and why it matters
How readily a tear runs through a film, normalised so that films of different gauge can be compared. That normalisation is the practical difference from the ASTM trouser method, which reports a force and leaves the thickness out — the two therefore produce different numbers in different units on the same material, and neither converts to the other. Because thickness is the divisor here, its measurement carries as much weight as the force measurement, and film gauge varies across a web more than most people assume.
Where the method stops working
The standard names both limits explicitly — too rigid and it fractures, too deformable and the legs absorb the energy.
- Thickness
- Less than 1 mm
- Specimen
- Rectangular with a longitudinal slit over half its lengthThe slit creates the two trouser legs that are pulled apart.
- Result
- Tear resistance in N/mmThe average force divided by the thickness. ASTM D1938 does not normalise, which is why the two do not match.
- Too rigid
- Not applicable if brittle fracture occurs
- Too deformable
- Not applicable if the energy deforming the legs is significant against the tearing energyAn unusually explicit statement of a limit most tear standards leave implicit.
- Cellular materials
- May not be suitable
Both flexible and rigid materials are in scope — the limits are behavioural, not categorical. What matters is whether the specimen fractures or whether its legs soak up the work.
Test speed
- Conditions
- Pre-treatment, temperature, humidity and speed all defined
- Reported
- Tear resistance in N/mm
- Averaging
- Over the tearing portion of the trace
- Measure thickness at several points along the tear path
- DakThe result is divided by thickness, and film gauge varies across a web more than people expect.
Calculations
Tear resistance—
Average tearing force divided by specimen thickness
- force
- the mean force over the tearing portion, N
- thickness
- specimen thickness, mm
Gives N/mm. Because the thickness is the divisor, an inaccurate gauge measurement passes into the result at full weight.
Why the leg-energy limit exists—
Work done stretching the legs is not work done tearing
The standard states this as a scope condition rather than leaving it to judgement, which is unusual and useful.
How the test runs
- 01Pre-treat and condition the specimens as specified.
- 02Confirm the material is under 1 mm thick.
- 03Measure the thickness at several points along the intended tear path.
- 04Cut rectangular specimens in the required directions.
- 05Cut the longitudinal slit over half the specimen length with a sharp blade.
- 06Fit pneumatic grips suited to thin film.
- 07Mount one leg in each jaw.
- 08Test at the specified speed, temperature and humidity.
- 09Record the trace and average the force over the tearing portion.
- 10Divide by the thickness to give tear resistance in N/mm.
- 11Reject specimens that fractured in a brittle manner or whose legs deformed substantially.
The fixture this method needs
What the report has to contain
- Reference to ISO 6383-1 and the edition
- Material identification and process
- Direction tested
- Measured thickness and where it was measured
- Pre-treatment, temperature and humidity
- Speed of testing
- Average tearing force and the length over which it was averaged
- Tear resistance in N/mm
- Observations of brittle fracture or leg deformation
- Number of specimens rejected and why
What the machine must be capable of
Very low force, well measured, and steady travel over a long tear. Trouser tear forces on film are commonly a few newtons, so the load cell is chosen for the material rather than the frame. Grips must hold thin, often slippery film without cutting it and without releasing partway through. Because temperature and humidity are specified conditions rather than incidental ones, a conditioned laboratory or a chamber is part of the requirement for materials sensitive to moisture.
What goes wrong in practice
Mixing ISO and ASTM trouser results in one data set, when one is normalised by thickness and the other is not. Measuring thickness at a single point when it is the divisor and the film varies. Averaging in specimens that fractured brittly or whose legs stretched substantially, both of which the scope excludes. And reporting a value without the speed, temperature and humidity, which for a rate- and moisture-sensitive polymer leaves the number uncheckable. Direction is the last of them: an oriented film tears far more readily along the draw than across it, and a result that does not say which way the specimen was cut describes the process as much as the material.
ISO 6383-1 or ISO 6383-2
| Part 1 — trouser | Part 2 — Elmendorf | |
|---|---|---|
| Principle | Force to propagate a tear | Energy to tear, by pendulum |
| Machine | A testing machine | A pendulum instrument |
| Reports | N/mm | Energy or force from pendulum swing |
| Comparable | No | No |
Two parts measuring tear by fundamentally different means. Part 1 is a controlled slow propagation on a testing machine; Part 2 is a rapid pendulum event. They do not rank films identically and neither converts to the other.
Questions we are asked about this test
What is ISO 6383-1?
It is the ISO trouser tear method for plastic film and sheeting less than 1 mm thick. A rectangular specimen with a longitudinal slit over half its length is pulled apart by its two legs under defined conditions of pre-treatment, temperature, humidity and speed, and the average force to tear it is divided by the thickness to give a tear resistance in newtons per millimetre.
Why is the result divided by thickness?
To make films of different gauge comparable. A thicker film tears at a higher force for that reason alone, so normalising by thickness isolates the material's behaviour from its gauge. The consequence is that the thickness measurement matters as much as the force one — it is the divisor, so an error in it passes into the result at full weight, and film gauge varies across a web more than people expect.
What are the two ways a material falls outside this method?
The standard names both, which is unusually explicit. If the material is so rigid that brittle fracture occurs during the test, the trouser geometry has stopped describing what happened. If it is so deformable that the energy used stretching the legs is significant compared with the energy used tearing, the measured force is no longer a clean tear resistance. Both limits are behavioural rather than categorical — flexible and rigid materials are otherwise both in scope.
Can I compare this with ASTM D1938?
Not directly. Both use a trouser geometry, but this method divides by thickness and reports newtons per millimetre while D1938 reports a force. The two are in different units and will not agree on the same film. Whichever was used has to be quoted with the value, and a data set should not mix them.
How does Part 1 differ from Part 2?
Fundamentally. Part 1 is a slow, controlled propagation on a testing machine, measuring the force to keep a tear running. Part 2 is the Elmendorf pendulum, a rapid event measuring the energy absorbed as a swinging arm tears through the specimen. They do not rank films identically, because rate-sensitive polymers behave differently at the two speeds, and neither result converts to the other.
Does it work on foamed or cellular film?
The standard says it may not be suitable. A cellular structure tears by crushing and collapsing cells rather than by propagating a crack through a continuous solid, so the trouser geometry's assumptions weaken and thickness becomes an especially poor divisor. If a cellular material must be characterised, that limitation should be stated in the report rather than left implicit.
Why are pre-treatment and humidity specified?
Because many films are sensitive to both. Moisture plasticises some polymers and changes their tear behaviour substantially, and residual stress from processing relaxes over time. Fixing the pre-treatment, temperature, humidity and speed together is what makes results reproducible between laboratories, and omitting any of them from the report leaves the value uncheckable.
Running ISO 6383-1 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 | Very low — trouser tear forces on film are commonly a few newtons | 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 tear force | ISO 7500-1 Class 0.5, verified to ASTM E4, DIN 51221 and BS 1610 |
| Gripping | Grips taking the two legs of the trouser specimen, one in each jaw | 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.