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Hardness tests on plastics

ISO 2039-1, ISO 2039-2, ISO 48-4, ISO 868, ASTM D2240, ASTM D785, ISO 19278

The plastics industry applies a variety of hardness testing methods, and each method addresses a different measurement objective. They can be in the nano, micro, or macro range.

Plastics brochure Test methods Shore ISO 48-4, ISO 868, ASTM D2240 Ball indentation ISO 2039-1 Rockwell ISO 2039-2/ASTM D785 Instrumented hardness testing ISO 19278 Videos Testing systems

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Methods for Hardness Testing

The polymer testing industry applies a variety of hardness testing methods, and each method addresses a different measurement objective. They can be in the nano, micro, or macro range.

Shore hardness ISO 868, ASTM D2240, ISO 48-1 and -4, ASTM D2240

  • Shore hardness is measured on plastics according to ISO 868 or ASTM D2240. The measurement procedure is simple and can be easily carried out with portable instruments. Hardness measurements to Shore are widely used for quality control purposes and belong to the macroscopic methods. For laboratory tests, we recommend using the instrument in combination with a test stand. Calibration of these instruments is described in ISO 21509.
  • The shore hardness on rubber and elastomers is measured according to ISO 48-1, ISO 48-4, ISO 48-7 or ASTM D2240. ISO 48-9 describes the instrument calibration. The main difference within the ISO standards compared to the measurement on plastics is the exposure time of the indenter.
  • In both cases, 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 load of the indenter. Shore hardness is shown on a scale from 0 to 100 Shore. The contact force of the contact foot of the instrument on the surface of the specimen determines the zero position. Depending on the standard this force is approximately 10 N for Shore A and approximately 50 N for Shore D.
  • A range of different Shore scales have been established due to different indenter forms and spring characteristics. The most common scales are Shore A and D. Other scales, such a Shore B, C, 0, 00, 000, and D0 were developed for specific applications. The range of applications starts with soft elastomers (Shore A) and ends with harder thermoplastics (Shore D).
  • Analog and digital Shore hardness tester
    ZwickRoell offers Shore hardness testers with analog or digital displays and PC connection options. The testing instruments are equipped with backlash-free linear ball bearings and operate with virtually no friction. The spring rate can be precisely adjusted during calibration to maintain the forces specified in the standards for every Shore value. In this way, the tolerances specified by the standards are adhered to exactly and high repeatability of the results is made possible.

More information on Shore hardness tests

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 test 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 hardness testing (ZHR4150) to ISO 6508, 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, ASTM E18 preload: 3 kg. Test load: 15, 30, 45 kg scales: N T W X Y
    • Universal Rockwell (ZHR8150) to ISO 6508, 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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