ASTM D2000 Standard Classification System for Rubber Products
ASTM D2000 Introduction
American Society of Testing and Materials (ASTM) provide a standardized method of calling-out the required physical properties of a rubber product, based primarily on its Type (Heat Resistance) and Class (Oil Resistance). Specifications for physical properties of elastomeric seals can be very general or extremely specific in nature.
Probably the most common general classification system is ASTM D 2000 Standard Classification System for Rubber Products in Automotive Applications. The purpose of this classification system is to aid in the selection of practical rubber products for specific environments. It also provides a line call-out designation for the specification of materials.
If the M is present, the unit of measure is expressed in Metric units. You will find the tensile strength, temperature and tear strength expressed in MPa, C, and kN/m. If the letter M is not present however, the unit of measure is in English units and the unit of measures will be psi, F, and ppi. Prior to 1980, all ASTM specifications were in English units. Beginning in 1980, the Metric unit callouts became the standard.
The Grade Number designates instances where more extensive tests are required. Any grade other than 1 mandates additional requirements that are spelled out in Table 6 of the D2000 document.
Indicated the Heat Resistance properties of the Elastomer.
Indicates the Oil Resistance properties of the elastomer as measured by volume swell under test procedures
The Shore A Durometer hardness requirement of the elastomer. In this case the 7 calls out 70 +/- 5 Durometer.
This indicates the minimum tensile strength of the elastomer. If the designation has an M after the Revision Year, then this callout is stated in Metric units, megapascals (MPa). If no M is present, then the callout is specifying the English unit, pounds-per-square inch (psi). In this example, the 14 is calling-out 14 MPa. The conversion to psi is: MPa x 145 = psi. Therefore, the psi Tensile Strength requirement of this designation is 14 x 145 = 2030 psi.Tensile strength is the maximum tensile stress reached in stretching a test piece (either an O-ring or dumbbell).Tensile tests are used for controlling product quality and for determining the effect of chemical or thermal exposure or an elastomer. In the latter case, it is the retention of these physical properties, rather than the absolute values of the tensile stress, elongation or modulus, is significant.
ASTM D2000 Suffix Letters (Test Requirement)
ASTM D2000 Suffix Numbers (Second Number)
ASTM D2000 Suffix Requirement Test
B14 EO14 EO34 F17 is the second half of the original sample ASTM line call-out. When reading the line call-out the suffix letter denotes the test method, The first suffix “number”, in our grouping, specifies the test method and duration of the test. The second number indicates the temperature at which the test is to be run.
Walk-ThroughIn our example we will use B14 as the first walk through. The first callout B, indicates a Compression Set requirement. We are now able to refer to “Table 5 ASTM Methods” in ASTM D2000-12 for all the details all suffix callout compositions and the respective requirements for each grade of polymer. Our first suffix number 1 specifies that the test be run in accordance with Test D395 Method B for 22 h, and that the material to be tested is a solid piece. The second suffix number in our grouping indicates the temperature at which the test is to be run. These temperatures are listed in Table 4. Our callout 4 indicates that suffix B polymers require a 100°C test temperature.
In all we need to the test be conducted with a solid piece and ran in accordance with Test D395 Method B for 22 hours at a temperature of 100 degrees Celsius.
Inserting additional call-outs, as shown above, should be used depending on your applications. If the rubber part will see high temperature exposure, it is wise to add a heat resistance requirement (A). This will add a tighter tolerance on physical property change after a heat age exposure. Many sealing applications are compression set-dependent, so using a compression set resistance call should give a more robust compound. Call-outs for Ozone, Fluid Aging, Low temperature, Tear, Adhesion and Staining can be used, but should be based on what the application will actually see.
can be added using a “Z” call-out. This is typically done after the last call-out and number. Below are a few examples that we have seen over time:
The various call-outs can be used to meet specific needs of an application. They can be used to specifically assure a given polymer time like, Z1- polymer EPDM, or to assure a specific grade–like Z1 – Medical Silicone.