ISO 6383-1 Plastics - Film and Sheets - Determination of resistance to tearing - Part 1: Trouser tearing method

The standard “ISO 6383-1 Plastics - Films and sheets - Determination of resistance to tearing - Part 1: Trouser tearing method” developed by the International Organization for Standardization (ISO) describes a test method for determining the tearing resistance of plastic film or sheet thinner than 1 mm in the form of standard trouser-shaped test specimens tested under defined conditions such as pretreatment, temperature, humidity and test speed.

This test method is applicable to films and sheets made of both flexible and rigid materials, provided that the material is not so hard that brittle fracture will occur during the test or is not irreversibly deformable and that the energy used in deformation of the specimen legs is not significant (i.e. negligible) compared to the energy used in rupture.

This method may not be suitable for determining the tear properties of cellular sheets and films.

For the purposes of this standard, the following terms and definitions apply:

• Tear strength refers to the average force required to propagate a tear at a constant tear rate along a test specimen conforming to the shape given in the standard.
• Tear strength expresses the tear force divided by the specimen thickness.

This method can provide data for quality control, acceptance or rejection, and research and development in accordance with specification requirements. Tear properties may vary with sample preparation, test speed, and test environment. Consequently, when definitive comparative results are required, these factors must be carefully controlled.

In principle, it is possible to compare the tear resistance of samples made of different materials as long as their thicknesses do not differ by more than plus/minus 10 percent. However, caution is required when interpreting such results, as the tear energy can vary significantly with the test speed for different materials.

In performing this test, a rectangular test specimen with a longitudinal slit running along more than half its length is subjected to a tensile test on the “trouser legs” created by the slit. The average force required to tear the specimen completely along its length is used to calculate the tear resistance of the material under test in N/mm.

The main equipment used in these tests includes:

• ISO 527-Tensile testing machine (not pendulum type) similar to that specified in standard 3 and having the following features:
  • It shall be power operated and capable of maintaining the appropriate clutch separation ratio specified in this standard. It is essential that the load measuring device is equipped with an autographic recording device which records the load applied to the specimen as a function of the time elapsed from the start of the test.
  • The grips shall be fitted with mandrels designed to hold the legs of the test specimen securely without slipping. The mandrels shall be wider than the width of the test specimen and shall not be mounted on swivel joints so that they remain parallel to each other during a test.
• Appropriate equipment for measuring the thickness of samples by the method described in ISO 4593. For embossed film or sheet, the device specified in ISO 4591 should be used.

Test samples must have the shape and dimensions shown in the figure in the standard. The length of the slit in the middle of the sample must be 75 mm plus/minus 1 mm.

Test specimens should be cut so that their edges are smooth and free of nicks. It is recommended that they be examined with a low-power microscope to check that they are free of nicks. It is important to pay particular attention to the tip of the slit in the middle of the specimen.

The properties of some film and sheet materials may vary with the direction in the plane of the film. In such cases it is essential to prepare two sets of test specimens whose principal axes are parallel and perpendicular respectively to the direction of a feature of the film or sheet that is either visible or inferred from knowledge of the method of manufacture.

The test direction is defined as the direction of the long axis of the test specimen.

In some types of film, for example in the case of machine direction test specimens, different tear resistance results may be obtained for any given test direction (e.g. machine direction or cross direction) depending on whether the tear propagation is in the direction of processing or against the processing direction. When this is known to occur, two sets of test specimens should be cut in the test direction and slit to obtain results for the two possible tear propagation directions.

At least five test specimens are tested in each of the required test directions. Specimens in which the tear extends beyond the line to one of the test specimen edges are discarded and additional specimens are tested.

The test speed must be one of the following:

• 200 mm/min plus/minus 10 percent
• 250 mm/min plus/minus 10 percent

Among the numerous tests, measurements, analyses and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the “ISO 6383-1 Plastics - Films and sheets - Determination of tear resistance - Part 1: Trouser tearing method” standard with its trained and expert staff and advanced technological equipment.