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Hardness tests on plastics

ISO 2039-1, ISO 2039-2, ISO 7619-1, ISO 868, ASTM D2240, ASTM D785, ISO 19278

There are a variety of methods used to test hardness in the plastics industry.and each method addresses a different measurement objective.They can be in the nano, micro, or macro range.

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Methods for Hardness Testing

There are a variety of methods used to test hardness in the plastics industry, and each method addresses a different measurement objective. They can be in the nano, micro, or macro range.

Shore Hardness (analog here) ISO 7619-1, ISO 868, ASTM D2240

  • Determination of Shore hardness to ISO 7619-1, ISO 868 and ASTM D2240 is a test method that can be easily performed with a portable hardness tester. The method is used widely in quality control and belongs to the macroscopic group of methods. Use of the instrument in combination with a test stand is recommended for laboratory tests.
  • The test measures the indention depth of the indenter in the material. The indenter is loaded by a spring with defined characteristics. The greater the hardness of the material to be tested, the smaller the indention depth; but the higher the indenter load. The test loads are 10 N for Shore A and 50 N for Shore D.
  • A range of different Shore scales have been established due to the variation in indenter forms and spring characteristics. The most well-known scales are Shore A and D. Other scales, such a Shore B, C, 0, 00, 000, and D0 apply to specific applications. This application area ranges from soft elastomers (Shore A) to thermoplastics (Shore D).
  • Digital Shore hardness tester
    ZwickRoell offers hardness testers to Shore with analog or digital displays and PC connection options.

Ball Indention Hardness ISO 2039-1

  • Ball indentation hardness to ISO 2039-1 is used widely in European laboratories. A spherical indenter with a diameter of 5 mm is pressed into the plastic specimen at a constant test load. The indention depth under load is the determining variable for the hardness value. The standard defines a selection of test loads so that the indention depth is limited to a range of 0.15 mm to 0.35 mm.
  • The high test loads and the deep indention allow for measurement across a large test surface and thus, a strong average of the measured value. This method is suitable for measuring both filled and unfilled plastics.

Rockwell Hardness Tester ISO 2039-2, ASTM D785

  • ISO 2039-2 and ASTM D785 define various Rockwell hardness scales for plastics testing.
  • In contrast to ball indention hardness, in which the indention depth is measured under load, with the Rockwell method, the indention depth is measured at a defined preload. There are a variety of indenters available that correspond to the Rockwell scale.

Instrumented Hardness Testing to ISO 19278 (Draft)

  • Hardness test methods based on continuous recording of the entire force-penetration behavior are known as instrumented hardness testing methods.
  • In addition to multipoint data in the form of a single hardness value, these methods generate complete curve sequences that demonstrate other interesting material characteristics. Instrumented, recorded hardness measurement is an extension of conventional hardness measurement.
  • In general, instrumented hardness measurement methods can be used in the nano, micro, or macro range. Indenters can have different geometries, for example, spherical, conical, four-sided pyramid shape (Vickers), or a three-sided pyramid shape (Berkovic).
  • Submicron-structured materials, their structures from a few nanometers to one micrometer can be measured with micro hardness methods. Filled or reinforced polymers and polymer blends are measured with macro methods, meaning a high load is applied. This prevents the matrix behavior or the fiber or filler from dominating the hardness value, producing data scatter that is too large.
  • Such a method has been standardized for metals as defined in ISO 14577-1. An initial draft of the standard to ISO 19278 exists for plastics.
Rockwell hardness testers
  • Rockwell hardness testers from ZwickRoell feature an indenter-holder for hardness testing at difficult-to-access locations.
  • Hardness testers in the ZHR product line cover the following methods:
    • Regular Rockwell methods (ZHR4150) to ISO 6508 and ASTM E18 preload: 10 kg. Test load: 60, 100, 150 kg scales: A B C D E F G H K L M P R S V
    • Superficial Rockwell methods (ZHR4045) to ISO 6508 and ASTM E18 preload: 3 kg. Test load: 15, 30, 45 kg scales: N T W X Y
    • Universal Rockwell (ZHR8150) to ISO 6508 and ASTM E18 preload: 3, 10 kg. Test load: 15, 30, 45, 60, 100, 150 kg scales: A B C D E F G H K L M N P R S Y V W X Y
    • Rockwell for plastics (LKP) to ISO 2039-2 and ASTM D785 (A&B)

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