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ASTM and BS Framework
A method for specifying rubber materials can be found in ASTM D2000 and BS 5176. These provide a full framework covering all rubbers and rubber properties. The relevant requirements for an application are selected from within the framework and are expressed in the form of a "line call out". (The same framework is used in both ASTM D2000 and BS 5176).
An example of a line call out is BS 5176 1MBC514 F2 7Z1. This can be broken down as follows indicated in this table:
The appropriate table for Grade 1 MBC materials shows the following basic requirements:
• Test: Elongation at Break
Requirement: 400% minimum
• Test: Heat Resistance (70 hrs @ 100°C)
Requirement: T.S. ± 30%, E.B. -50% max, Hardness ±15° max
• Test: Oil Resistance (Oil no.3 70 hrs @ 100°C)
Requirement: Volume change + 120% max
• Test: Compression Set (22 hrs @ 100°C)
Requirement: 80% max
F27 is a low temperature modulus test to BS 903 A13. For Grade 1 MBC materials the requirement is for a modulus of 70MPa at -40°C (i.e. rubber is still flexible at -40°C).
Z1 indicates an additional special requirement. This would be shown on the drawing e.g. Z1 = red colour required.
The following specifications cover rubber materials for general applications:
BS 1154 Natural Rubber compounds
BS 2751 Nitrile Rubber compounds
BS 2752 Chloroprene (Neoprene) Rubber compounds
BS 3222 Low compression set Nitrile compounds.
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