Hardness Test

Hardness Test:

1. Hardness is defined as the resistance of a material to deformation, particularly permanent.

deformation by indentation or scratching.

2. Two most commonly used hardness tests for plastics are the Rockwell hardness test and

the Durometer hardness test.

3. Rockwell ASTM D 785, ISO-2039, JIS-K7202, DIN-53426 hardness for relatively hard

plastics such as acetals, nylons, acrylics and polystyrenes.

4. Durometer ASTM D 2240, ISO-868, JIS-K 7215, BS2782 Method 307 A and DIN 53505

hardness for flexible PVC rubbers, polyethylene & polyurethane.

Comparison of Ball, Rockwell and Shore hardness

1. The Rockwell hardness test determines the hardness of plastics after allowing for elastic recovery of the test specimen.

2. This is different from both Ball and Shore hardness: in these tests, hardness is derived from the depth of penetration under load - thus excluding any elastic recovery of the material.

3. Rockwell values CANNOT, therefore, be directly related to Ball or Shore values.

4. Ranges for Shore A and D values can be compared to ranges for Ball indentation hardness values. A linear correlation, however, does not exist.