DIN 53357 Testing of Plastic Sheets and Films - Layer Separation Test

The standard "DIN 53357 Testing of plastic sheets and films - Layer separation test," developed by the German Institute for Standardization (DIN), describes a test method used to assess the adhesion of layers to each other or of upper layers to the substrate. This method determines the separation force. This test method can be applied to products in accordance with DIN 16922. Depending on the product type, two methods, Method A or Method B, can be used. The method must be agreed upon.

For the purposes of this standard, separation force refers to the force required to separate two layers from each other or an upper layer from a lower layer, as determined in accordance with this standard.

When performing this test, any tensile testing machine conforming to the "DIN 51221 Tensile Testing Machines" standard, with low-inertia force measuring equipment meeting Class 1 requirements as defined in the "DIN 51220 Material Testing Machines" standard, can be used. The force measurement range of the testing machine should be selected so that the average separation force does not lie within the first fifth of the measurement range. The tensile force acting on the sample can be recorded.

Sampling and pretreatment must be carried out in accordance with the standard "DIN 16906 Testing of plastic sheets and plastic films - Samples and specimens - Preparation and conditioning." The shape and number of samples are determined as follows:

• For the Method A separation test, five specimens, each 200 mm long, should be taken lengthwise and crosswise from the web. For plastic composite sheets, the test specimens should be 50 mm wide plus/minus 1 mm. For multilayer plastic films according to DIN 16922, test specimens with a width of 15 mm plus/minus 1 mm can be used.
• For the Method B split test, five test specimens, each 15 mm plus/minus 1 mm wide and 250 to 300 mm long, shall be taken across and across the slab.

When preparing test specimens, the layers to be separated are mechanically separated, if possible along a narrow edge of the specimen and parallel to its surface, for a length of at least 40 mm. The layers themselves should not be significantly damaged.

If separation of the layers is not possible, this can be facilitated, if necessary, by immersing the sample in a suitable solvent or solvent vapor for a length of approximately 40 mm. The solvent should then be removed by drying at a temperature not exceeding 70°C. If the top layer cannot be separated from the substrate even after this treatment, the test cannot be performed. For thin top layers whose strength is less than the separation force, the bond can be enhanced by bonding the two samples (top layer to top layer) with a solvent-free polyurethane adhesive. Only one of the top layers is mechanically separated for a length of approximately 40 mm, as described above. After preparation, the test samples are pretreated in accordance with this standard.

Although largely superseded today by ISO standards such as ISO 4593, DIN 53357 is historically important in materials testing, particularly for evaluating the properties of plastic films and sheets. This standard is considered important for the following reasons:

• Standardized tests for plastics: The DIN 53357 standard provides a consistent methodology for testing the mechanical properties of plastic films, such as tensile strength, elongation, and tear resistance. This ensures reliable and comparable results across different laboratories and manufacturers.
• Quality control: This standard is critical for quality assurance in industries like packaging, where plastic films are widely used. It allows manufacturers to verify that materials meet specific performance criteria, ensuring durability and functionality.
• Adhesion testing: A key aspect of the DIN 53357 standard is its focus on testing the adhesion properties of laminated or coated films. This is vital for applications where the bond strength between layers directly impacts product performance (e.g., in multilayer packaging or tapes).
• Industry benchmark: As a German standard, this standard served as a benchmark for European industries before the wider adoption of international standards such as ISO. It facilitated trade and collaboration by providing a common framework for material specifications.
• Safety and reliability: By defining test conditions and procedures, the DIN 53357 standard helps ensure that plastic films used in critical applications (e.g. medical packaging, food safety) meet stringent safety and reliability requirements.

As a result, modern standards such as ISO 4593 or its ASTM equivalents have largely superseded DIN 53357. However, it has nevertheless contributed significantly to the establishment of rigorous and reproducible testing protocols that improve the quality and performance of plastic materials across various industries.

Focusing primarily on the testing of plastic films and sheets, the DIN 53357 standard includes specific test methods for evaluating mechanical and adhesion properties. These methods are specifically designed to evaluate the performance of plastic films in applications such as packaging, laminates, and coatings. The main test methods are:

• Adhesion test (peel test): The purpose of this test is to measure the bond strength between layers of laminated or coated plastic films, such as multilayer packaging or adhesive tapes. A peel test is performed in which the layers of a laminated film are separated at a specified angle (usually 180 degrees or 90 degrees) using a tensile testing machine. This standard specifies parameters such as peel rate, sample width, and environmental conditions (e.g., temperature and humidity) to ensure consistent results.
• Tensile testing: The purpose of this test is to evaluate the mechanical strength and elasticity of plastic films, including tensile strength (the force required to break the film) and elongation at break. A strip of film is clamped in a tensile testing machine and stretched at a constant rate until it breaks. This test determines tensile strength, elongation at break, and yield strength (if applicable).
• Tear resistance test: The purpose of this test is to measure the tear resistance of a plastic film, which is crucial for assessing durability in applications such as bags or packaging. A pre-cut sample (usually with a small initial tear) is subjected to a tearing force using methods such as the Elmendorf tear test or the trouser tear test. The force required to propagate the tear is recorded.
• Bond Strength Testing for Coated Films: The purpose of this test is to evaluate the bond strength between a plastic film and a coating (e.g., lacquer, ink, or adhesive). Similar to the peel test, this test involves measuring the force required to separate the coating from the substrate. Specialized equipment may be used to initiate and propagate the separation.
• Sample preparation and conditioning: The goal of this process is to ensure consistent and reproducible results. This standard specifies how samples should be cut, stored, and conditioned (e.g., at specific temperature and humidity levels) before testing to eliminate variability due to environmental factors.

Many methods from DIN 53357 have been incorporated into or superseded by ISO or ASTM standards, but the principles remain similar.

Our organization, which has been supporting businesses across all sectors for years with a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the DIN 53357 "Testing of plastic sheets and films - Layer separation test" standard.