Full definition
DIN 53505 is a German standard that outlines the procedure for determining the Shore hardness of rubber and plastics using a durometer. This standard is functionally equivalent to ASTM D2240, which is commonly used in the United States, but there is a significant procedural distinction between the two. Specifically, DIN 53505 mandates a reading time of three seconds, whereas ASTM D2240 specifies a one-second reading. This difference is crucial because rubber materials tend to deform under the durometer's indenter after initial contact. Consequently, the longer reading time of three seconds generally results in readings that are 1-3 Shore A points lower than those obtained with a one-second reading on the same specimen. Thus, when comparing hardness values from different sources, it is essential to indicate which standard was employed to ensure accuracy and consistency.
The testing conditions prescribed by DIN 53505 require that the specimen be at least 6 mm thick and have a flat surface. The tests should be conducted at a controlled temperature of 23±2°C, and a minimum of five readings should be taken and averaged to obtain a reliable hardness value. This standard is widely referenced in European and many Latin American rubber specifications, particularly for products that are manufactured according to DIN or EN standards. In addition, ISO 48-4 serves as the international equivalent of DIN 53505, detailing methods for both IRHD (International Rubber Hardness Degrees) and Shore hardness testing, which also follows the three-second reading criterion.
For commercial specifications, it is common practice to state hardness values in a format that accommodates both standards. An example would be "60±5 Shore A per ASTM D2240 or DIN 53505," which provides clarity to stakeholders regarding compliance with either standard. This ensures that the hardness ratings of rubber products meet the necessary industry requirements and are suitable for their intended applications. Understanding the nuances of these hardness testing standards is critical for engineers and quality assurance professionals working within the rubber and plastics industries.