Rubber Parts and Materials: How to Read ASTM D2000 Specifications

A key challenge for buyers of rubber parts is how to specify and communicate the desired material requirements to a supplier. Accurately communicating the desired material requirements ensures that the right compound will be selected and used in the production process, and that the finished part will fully satisfy all the application requirements.

What is the ASTM D2000 standard?

For parts used to service automotive or industrial applications, the standard widely used for communicating the specifications of the rubber compound to be used is the ASTM D2000 standard (Standard Classification System for Rubber Products in Automotive Applications). As the ASTM D2000 standard notes, the ASTM D2000 classification system is based upon the idea that the properties of all rubber products can be arranged into characteristic material designations. These designations are determined by types, based on resistance to heat aging, and classes, based on resistance to swelling in oil. The standard thus establishes basic levels for materials, together with values describing additional requirements, which permit a complete description of all elastomeric materials.

The purpose of the ASTM D2000 classification system is to provide guidance to material engineers and specialists in the selection of elastomeric materials to service a given application, and to provide a method for specifying these materials through the use of a “line call-out” designation. Using an ASTM D2000 line call-out, a customer can communicate their material requirements completely and accurately to a supplier.

How does an ASTM D2000 line call-out work in practice? Below we explain how.

ASTM D2000 line call-out example

Here is an example of a typical ASTM D2000 line call-out for a rubber compound:

ASTMD2000-12M3CA710A25B35C32F17G21Z1, Z1= {Test method, desired result}

This line call-out can be broken down into the following components:

  1. The version of the standard used in the line call-out, and the units of measure.

  2. The material grade, type and class to be used by the supplier.

  3. The durometer and tensile strength of the compound to be used.

  4. Special requirements to be noted.

Using our example line call-out, and reading the call-out from left to right, here is how this specification would be read:

Standard version and units of measure

ASTM D2000-12 signifies that the 2012 version of the ASTM D2000 standard is being cited in the specification. Because the ASTM D2000 standard gives test protocols for rubber compounds, the latest version of the standard should always be used and referenced in the line call-out.

M designates the units of measure used to specify the compound. In this example, M means metric (International System of Units, or SI) units of measure are being used.

Material grade, type and class

3 designates the grade number of the rubber compound to be used. The ASTM D2000 standard contains tables showing various grades of rubber, where the grade number designates instances where more extensive material tests are required. A grade number other than 1 mandates additional requirements that are spelled out in the ASTM D2000 standard.

C designates the material type, which indicates the resistance of the material to temperature and heat aging. Material type is based on changes in tensile strength of not more than ±30%, elongation of not more than -50%, and hardness of not more than ±15 points after heat aging for 70-hours at an appropriate temperature. The temperature at which a material is to be tested for determining type is listed in a table contained with the ASTM D2000 standard. The standard designates 10 material types, using letter codes from A through K, depending upon the test temperature specified.

A indicates the class of the compound, based upon the resistance of the material to swelling in IRM 903 oil, after a 70-hour immersion at a specified temperature not to exceed 150°C (the upper limit of oil stability). Again, a table within the standard is used to determine the material class by letter code, depending upon the specified maximum volume swell %.

Durometer and tensile strength

7 designates the hardness of the compound, or durometer. In this case, 7is equal to a Shore A durometer of 70.

10 designates the minimum tensile strength of the compound. Since the units in this example are metric, 10 means a minimum tensile strength of 10MPa.

Special requirements to be noted

The remainder of our example line call-out are the so-called “suffix requirements.” These suffix requirements indicate any additional testing requirements that are needed to satisfy the specification callout. Each requirement is designated by a suffix letter, calling out the property to be tested, together with suffix numbers which call out the test method and test temperature (if required). The ASTM D2000 standard details 17 types of tests that can be carried out, each type with test methods and temperatures, all designated by a combination of letter and number codes.

In our line call-out example, the A in the A25 suffix means that a heat resistance test is required, where 2 indicates that the test method is ASTM D965, and 5 indicates that the test temperature range is from -25°C to 125°C. The values for the suffix letters and numbers are contained within the ASTM D2000 standard. Continuing with the suffix requirements in our line call-out example, B35 indicates a compression set test as being required, C32 an ozone resistance test, F17 a low temperature test, and G21 a tear resistance test. Z1 is an additional suffix which allows an engineer to customize a line call-out outside the parameters of the specification, including the exact rubber compound to be used. The Z1 suffix MUST be defined in the line call out as above. There are no limitations to the number of Z suffixes.

Buyers and material engineers should familiarize themselves with how D2000 line call-outs work in practice. Familiarity with ASTM D2000 line call-outs will ensure that material requirements and specifications are completely and accurately communicated to parts suppliers. The latest version of the standard, ASTM D2000-18, can be obtained through the ASTM website.

A significant portion of CRG’s production of parts for automotive and industrial applications is carried out using ASTM D2000 line call-outs communicated by our customers. These line call-outs help us to ensure that right rubber compounds are selected for parts production and that the finished part will fully conform to all customer requirements.

If you are sourcing or buying rubber parts for automotive or industrial applications, CRG will be pleased to review your needs. Our experienced team will recommend the appropriate material and produce the finished parts to your exact specifications.

To find out more about the rubber parts we can supply, please contact our sales team at