ISO 6383-1 Trouser Tear Testing of Plastic Film and Sheeting

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, the jaws starting 75 mm apart, and they are separated at 200 mm/min ± 10 % or 250 mm/min ± 10 % — clause 9 permits either, and the one used is reported — 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

Speed of testing

200 mm/min ± 10 %, or 250 mm/min ± 10 %Clause 9 permits either. A note in the same clause records that both are in common use worldwide and that a later revision might retain only 200 mm/min, so 200 mm/min is the rate to set where no material specification governs. Whichever is used is reported.

Initial grip separation

75 mmSet before the specimen legs are clamped and aligned on the grip centre line.

Conditions

23 °C/50 % relative humidity to ISO 291, or 23 °C alone where the material is known not to be humidity-sensitive

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.

What the machine must be capable of

Very low force, well measured, and steady travel over a long tear at either of the two rates the method allows: 200 mm/min ± 10 % or 250 mm/min ± 10 %, from an initial jaw separation of 75 mm. A note in clause 9 records that both are in common use worldwide and that a later revision might keep only 200 mm/min, so the figure to set where nothing else governs is 200 mm/min. 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.

The fixture this method needs

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.

Specifications

How the test runs

1. 01Pre-treat and condition the specimens as specified.
2. 02Confirm the material is under 1 mm thick.
3. 03Measure the thickness at several points along the intended tear path.
4. 04Cut rectangular specimens in the required directions.
5. 05Cut the longitudinal slit over half the specimen length with a sharp blade.
6. 06Fit pneumatic grips suited to thin film.
7. 07Mount one leg in each jaw.
8. 08Test at 200 mm/min or 250 mm/min, in the conditioning atmosphere.
9. 09Record the trace and average the force over the tearing portion.
10. 10Divide by the thickness to give tear resistance in N/mm.
11. 11Reject specimens that fractured in a brittle manner or whose legs deformed substantially.

Calculations

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, and which of the two permitted rates was used
• 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 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.