Hardness of plastics

ASTM D 785-89 Standard Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials, 5 pp (DOD Adopted) (FSC 9320) (MR) (Comm D-11)... 

ASTM D785-93, "Rockwell Hardness of Plastics and Electrical Insulating Materials," Philadelphia (1993). 

ISO R868. 1968. Determination of Indentation Hardness of Plastics by Means of a Durometer (Shore Hardness). 

A remarkably large discrepancy between the hardness of plastically deformed single crystalline volumes and of polycrystalline microstructures with grains of the same size, indicates a significant contribution of grain-boundary deformation at the indentation site in polycrystalline alumina, even at room temperature and even for coarse microstructures. 

Standard test method for Rockwell hardness of plastics and electrical insulating materials... 

Prandtl, L. 1920. Uber die harte, plastischer Korper (On the hardness of plastic bodies). Naohr.Kgl.Ges.Wiss. Gottingen, Math. Phys. Kl. 

Measure of the indentation hardness of plastics, usually xmderstood as hardness measured by the Shore... 

Rockwell hardness—ASTM D785. Hardness of plastics is difficult to establish and compare because there is an enormous range and there is an elastic recovery as well. However, the Rockwell hardness is useful in determining the relative indentation hardness between plastics. An indenter is placed on the surface of the test specimen and the depth of the impression is measured as the load on the indenter is increased from a fixed minimum value to a higher value and then returned to the previous value. A number of different diameter steel balls and a diamond cone penetrator are used. The Rockwell scale refers to a given combination of indenter and load. M80 places this resin in the upper middle range of hardness for plastics. A number of scales are used within the plastics industry. Figure 8.7 illustrates the relationship between them. 

Hardness of plastics is difficult to establish and compare because there is an enormous range of values. Hardness measured by indentors is also difficult because there is an elastic recovery effect. Among the most important methods for testing this property are Ball hardness, Rockwell hardness, and Shore hardness. Olher methods are also commonly used. The Rockwell hardness test determines the hardness after allowing for elastic recovery in the test specimen. Both Ball and Shore hardness tests exclude any elastic recovery effects. 

Shear test see D2344 Brittleness temperature by impact Rockwell hardness of plastics and electrical insulating materisds Determination of relative viscosity and moisture content of polyamide (PA)... 

ASTM D785 n An American Society for Testing of Materials (ASTM) standard test method for determination of indentation hardness of plastics by a Rockwell tester. The hardness number is derived from the net increase in the depth of impression as the load on a ball indenter is increased from a fixed minor load (10 kg) to a major load and then returned to the minor load. This number consists of the number of scale divisions (each corresponding to 0.002 mm vertical movement of the indentor) and scale symbol. Rockwell scales, designated by a single capital letter of English alphabet, vary depending on the diameter of the indentor and the major load. 

Standard Test Method for Rockwell Hardness of Plastics and Electrical... 

The hardness of plastics (and coatings may be considered to be very thin plastics) is most commonly measured by the Shore (durometer) test or Rockwell hardness test. Both of these hardness methods measure the resistance of plastics toward indentation. This provides an empirical hardness value. Shore hardness most often uses either the Shore A or the Shore D scale. These methods are best used for rubbers or elastomers and are also commonly used for softer plastics such as polyolefins, lluoropolymers, and polyvinyls. The Shore A scale is used for softer rubbers while the Shore D scale is used for harder ones. This method works better for thicker coatings, as with all hardness tests on coatings. The hardness of thin coatings can be influenced by the substrate, that is, an artificially hard measure may be measured. A picture of a durometer is shown in Fig. 2.23. 

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