Overview
EN ISO 2039-2:1999 specifies a standardized procedure to determine the indentation hardness of plastics using the Rockwell hardness tester. The method uses a constant minor load followed by a major load on a ball indentor and derives a Rockwell hardness number from the net increase in penetration depth. The standard highlights the effect of creep and recovery on results and provides instructions for apparatus, specimen preparation and measurement reporting.
Why this matters: repeatable Rockwell hardness values support material selection, quality control (QC), component design and conformity assessment for polymer products.
Key Topics
- Scope and principle: Indentation hardness measured by net increase in depth when load is raised from a fixed minor load to a major load and returned to the minor load.
- Loading and timing: The minor load is applied first; the major load must be applied within the specified interval after the minor load and readings are taken after the prescribed dwell times. Time factors are critical for materials with high creep and recovery.
- Measurement equation: The Rockwell hardness number (HR) is related to penetration: HR = 130 - e, where e is the depth of impression after removal of the major load (in units of 0.002 mm) for the specified scales.
- Apparatus: A standard Rockwell hardness tester with ball indentor, depth-measuring device (0.001 mm resolution desirable) and suitable load-application mechanism is required. Machines should be mounted on rigid, vibration-damped bases and calibrated periodically.
- Specimen requirements: Standard test specimens are flat sheets at least 6 mm thick (or stacks of same-material sheets). At least five measurements on isotropic materials are recommended.
- Scales: The standard covers Rockwell M, L and R scales; the minor load for these scales is 98.07 N. Scale-specific major loads and indentor diameters are defined in the standard; the Rockwell result is reported with the scale letter prefix.
Applications
- Quality control and production testing of polymer parts and compounds
- Material selection and comparative hardness ranking for design engineers
- Failure analysis where surface indentation resistance is relevant
- Calibration and cross-checking of hardness testing equipment in polymer labs
Practical considerations: allow for conditioning in the specified atmosphere prior to testing, avoid testing too near specimen edges (minimum spacing rules apply), and use the next severer scale when readings exceed the recommended range to maintain accuracy.
Related Standards
- ISO 2039-1 - Ball indentation method for plastics (related hardness metric)
- ISO 291 - Standard atmospheres for conditioning and testing
- ISO 868 - Shore hardness for plastics (alternative for less severe scales)
- ISO 48 - Hardness of vulcanized rubber (related indentation testing practices)
For implementation, refer to the full EN ISO 2039-2:1999 text for exact load values, timing tolerances, calibration procedures and reporting templates. The standard provides the technical detail necessary to obtain consistent, repeatable Rockwell hardness data for plastics.
