DIN 53435 Testing of Plastics - Bending Test and Impact Test on Dynstat Test Specimens

The standard “DIN 53435 Testing of plastics - Bending test and impact test on Dynstat test specimens”, published by the German Institute for Standardization (DIN), describes two different test methods: dynamic impact bending test and (semi)static bending test, as well as the Dynstat test specimens and Dynstat devices used in these tests.

The impact bending test specified in this standard can be used to examine the behavior of Dynstat test specimens under specific impact test conditions and to evaluate the brittleness or toughness of plastics within the limits defined by the test conditions. The method can also be used to obtain comparative data for similar material types.

The bending test specified in this standard can be used to examine the behavior of Dynstat test specimens under a specific four-point bending test condition and to evaluate the strength or toughness of plastics under quasi-static test conditions within the limits defined by the test conditions. The method can also be used to obtain comparative data for similar material types.

Both tests are primarily used for quality control and comparing different types of plastics. When comparing test results, care should be taken to ensure that the dimensions and condition of the test samples and the test conditions are the same.

The DIN 53435 standard includes methods for determining the mechanical properties of plastics under bending and impact loading using small Dynstat test specimens. These methods are useful for quality control, material comparison, and evaluating the toughness or brittleness of plastics, especially when limited quantities of material are available (due to the small specimen size).

The sample dimensions are small (typically around 10 mm x 4 mm x 15 mm or similar), making the method suitable for testing thin sections, prototypes, or materials available in limited quantities. The test uses a Dynstat device (a specialized pendulum tool for low-energy impact and bending). The results help to evaluate the relationship between brittleness and toughness under given conditions (such as temperature and the presence of notches). It is primarily used for quality control and comparison purposes rather than absolute design values.

The DIN 53435 standard is still in use, however, many modern tests have shifted towards compatible international equivalents. Specifically,

Charpy notched/unnotched impact test (ISO 179-1 and ISO 179-2 standards)
Izod impact test (ISO 180 standard)
General bending properties (ISO 178 standard)

Recent revisions have brought the DIN 53435 standard more closely aligned with these ISO standards, allowing for better comparison of results.

This standard is commonly used in the following areas:

Plastics processing and composite industries
Automotive and electrical component qualification
Material supplier data sheets (especially for rigid and semi-rigid thermoplastics and thermosets)
Investigation and failure analysis of small plastic parts.

In short, the DIN 53435 standard provides a compact and versatile method for the bending and impact characterization of plastics using the classic Dynstat system. Although partially superseded by ISO methods in global contexts, the latest revision ensures its validity for specific applications, continuity of legacy data, and situations requiring small test specimens.

Typical sample requirements include:

Shape: Rectangular or cubic.
Typical dimensions: Usually around 50 mm x 50 mm x 50 mm (depending on material thickness).
Cutting method: Samples must be cut cleanly to avoid damaging the cellular structure.
Key sample characteristics:
The cells should not be crushed during preparation.
The surfaces must be parallel and flat.
The test direction can be parallel or perpendicular to the foam rise direction.

The following equipment is required for the tests:

Universal testing machine capable of compression loading.
Parallel compression plates
Force measurement system
Deformation or displacement measuring device

The testing machine must apply the load at a controlled and constant speed to ensure repeatability.

In general, the testing method follows these steps:

Conditioning: Samples are conditioned in a standard atmosphere (typically 23 degrees Celsius and 50 percent relative humidity).
Sample placement: To ensure uniform load distribution, the test sample is centered between the compression plates.
Compression loading: The sample is compressed at a constant rate, typically around 10 percent strain per minute, or another defined rate.
Data logging: Force and deformation are continuously recorded during the test.
End of test: The test will be stopped in the following situations:
When the sample reaches a specified strain level (e.g., 10 percent deformation).
When structural collapse or failure occurs.

DIN 53435 generally reports the following important parameters:

Compressive strength: The maximum compressive stress a material can withstand before reaching a defined level of failure or deformation.
Compressive stress at a specific strain: Measured at 10 percent strain, a typical value often used for foam comparisons.
Compression modulus: The slope of the stress-strain curve in the elastic region represents stiffness.
Deformation behavior: The shape of the stress-strain curve shows how the cell structure collapses under load.

The DIN 53435 test is widely used in industries where rigid foams need to bear loads. Typical applications include:

Building:
Roof insulation panels
Wall insulation panels
Structural sandwich panels
Automotive:
Energy-absorbing foam components
Interior structural foam parts
Packaging:
Protective packaging foams
Cushioning materials for heavy products.

Tests according to the DIN 53435 standard help engineers in the following areas:

Comparing different foam formulations.
To ensure consistent product quality.
To determine suitability for freight handling applications.
Optimizing density and cell structure

Rigid foams exhibit a characteristic three-stage compression behavior:

Elastic region: Initial linear deformation.
Plateau region: Bending and collapse of the cell wall.
Condensation: The cells completely collapse and the tension rapidly increases.

Understanding this behavior is crucial for the design of materials used in insulation and structural applications.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services in accordance with the DIN 53435 standard.