ASTM D785 / ISO 2039 Rockwell Hardness Testing for Plastics
Rockwell Hardness test by ASTM D785, ISO 2039 evaluates indentation hardness of plastics and plastic-related electrical insulating materials. A Rockwell hardness tester is used to carry out the test. The hardness calculation is dependent on the net increase in depth of impact when a load is applied.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
Overview
ASTM D785 and ISO 2039 provide test methods for measuring the Rockwell indentation hardness of plastics and plastic-related electrical insulating materials. The Rockwell indentation hardness test measures a material’s resistance to indentation by applying a specified load with a Rockwell hardness tester.
The hardness of the material is determined by the net increase in indentation depth after the application of the major load, followed by its removal. Rockwell hardness is indicated on the R, L, M, E, and K scales, with higher values indicating greater resistance to indentation.
Scope, Applications, and Benefits
Scope
The ASTM D785 test evaluates indentation hardness in plastics and electrical insulating materials according to Rockwell hardness testing procedures. The test measures indentation hardness value by measuring changes in indentation depth with a specified load.
ASTM D785 evaluates:
- Rockwell indentation hardness of plastics
- Resistance of materials to indentation under load
- Hardness behavior using multiple Rockwell scales
- Performance of plastic electrical insulating materials
- Relative hardness comparison between plastic materials
Applications
- Plastic components used in industrial equipment
- Electrical insulation materials
- Consumer plastic products
- Plastic sheets and molded parts
- Automotive plastic components
- Materials research and product development
Benefits
- Provides standardized hardness values for plastics
- Supports comparison between plastic materials
- Assists in evaluating durability and wear resistance
- Helps in selecting materials for specific applications
- Supports manufacturing and product evaluation
Test Process
Sample Preparation
The plastic specimen is prepared with a smooth surface and placed on the Rockwell hardness tester.
1Minor Load Application
A preliminary load is applied, and the dial indicator is set to zero.
2Major Load Application
The main load is applied for a specified time to produce an indentation in the specimen.
3Data Recording & Evaluation
After removing the major load, the hardness value is read directly from the tester dial.
4Technical Specifications
| Parameter | Details |
|---|---|
| Applicable Materials | Plastics and electrical insulating materials |
| Specimen Thickness | Typically about 6.4 mm (0.25 in) |
| Hardness Scales | R, L, M, E, and K scales |
| Measurement Principle | Net increase in indentation depth under load |
| Measured Outputs | Rockwell hardness value |
Instrumentation Used for Testing
- Rockwell hardness testing machine
- Diamond or steel ball indenter
- Specimen support anvil
- Load application mechanism
- Dial indicator or digital hardness display
- Sample holding fixtures
Results and Deliverables
- Rockwell hardness values
- Hardness scale identification (R, L, M, E, or K)
- Indentation depth measurement results
- Test condition summary
- Compliance report
Frequently Asked Questions
Plastic Rockwell hardness is measured by ASTM D785 and ISO 2039, which measure the resistance to indentation, providing comparative hardness values that are useful in evaluating the rigidity and performance of plastics.
In testing using ASTM D785 or ISO 2039, a small load and then a major load are applied. The hardness value is computed from the indentation depth difference, giving a Rockwell hardness reading depending on the plastic scale.
Rockwell hardness tests are fast, simple, and consistent. ASTM D785 and ISO 2039 standards offer reliable hardness values that assist in comparing materials, ensuring product consistency in production, and testing resistance against surface indentation.
ASTM D785 and ISO 2039 are commonly used standards for testing thermoplastics, thermosets, reinforced plastics, and rigid polymers used in automotive parts, electrical components, consumer products, and equipment across industries.
ASTM D785 and ISO 2039 standards test for surface indentation hardness only and do not test for tensile strength or impact resistance. Material thickness and surface finish can affect test scale selection for hardness testing.
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