The ASTM D 2000 classification provides a system to
standardize the properties of rubber materials. This classification was
originally developed for use in the automotive industry but has since become the
accepted specification for a variety of industries. The American
Society of Testing and Materials (ASTM) “call out” is a useful tool because it
ensures rubber material qualities and performance remain consistent across
manufacturers.
This is beneficial as it gives buyers the flexibility to
source elastomeric materials from different manufacturers without compromising
quality. Initially, an ASTM 2000 “call out” may look like a chaotic
alphanumeric code, but it can be simplified and broken down into manageable
pieces. At the basic level, ASTM D2000 identifies rubber products based on
their resistance to heat ageing and resistanceto swelling in oil. In addition
to the elastomeric types determined by heat resistance andoil swell, the “call
out” also identifies grades or levels of test requirements, hardness and
tensile strength. These characteristics will typically help identify the base
rubber material. The “call out” will also include a combination of alphanumeric
characters at the end of the code, called a suffix, that further define the
elastomeric properties.
The following example will assist you in understanding an
ASTM “call out”.
ASTM D
2000 - M 5BG 407 A14 B14 E014 E034 F17
The first part of the code identifies the document name.
There will typically be a two
digit code after the dash that indicates the revision year.
ASTM D 2000 M 5 BG 407 A14 B14 E014 E034 F17
M – the letter “M” indicates the unit of measure, in this
case is metric. If no M is present then the standard unit of measure is English
units. In this example, for instance, the tensile strength would be measured in
megapascals (Mpa) as opposed to the English standard pounds per square inch
(psi).
ASTM D 2000 M 5 BG 407 A14 B14 E014 E034 F17
Grade Number – this position in the call out indicates the
grade of the material required. A 1 in this position means that only the basic
minimum test requirements are needed. Any number 2, 3, … 8 in this position
indicates that additional tests are required. In the above example, the grade
requirement is 5, indicating that more tests are required to ensure the correct
material is supplied. These tests are outlined in Table 6 of the ASTM document.
ASTM D 2000 - M 5BG 407 A14 B14 E014 E034 F17
Type and Class – the letters in this position indicate the
type and class of elastomer. The first letter, in this example B, identifies the heat
resistance properties of the elastomer. The second letter, in this case G, identifies the
elastomer based on its oil resistance as measured by percentage volume swell in ASTM
Oil # 3. Therefore, in the example above, BG represents an elastomer with heat
resistance up to 100C / 212F, and a max volume swell of 40%.
The chart below shows approximately where the basic rubber
materials fall based on heat resistance and volume swell. From this chart, the
BG code in the example above identifies a nitrile elastomer.
ASTM D 2000 M 5 BG 407 A14 B14 E014 E034 F17
Hardness / Tensile Strength - The next three digits
indicate the hardness and minimum tensile strength requirements for the elastomer. The
first digit, 4, identifies the hardness measured in Shore A units +/- 5. The
next two digits, 07, are used to identify the minimum tensile strength of the
elastomer. In the example, the call out identifies an elastomer with an initial
Durometer of 40 +/- 5, and minimum tensile strength of 7 MPA. Note, since the
unit of measuring for the call out is metric as indicated by the “M” the
tensile strength unit of measure is megapascals. If there was no “M” present
then the unit of measure would be the English unit PSI (pounds per square inch).
The psi conversion is roughly MPa x 145. In the above example 07MPa = 1,015
psi. The first three codes, Grade, Type/Class and
Hardness/Tensile Strength are all that is needed to identify a general material
type such as nitrile(NBR) or viton(FKM). Additional requirements and/or
performance characteristics of the elastomer will be identified by a suffix
appended to the end of the code after the hardness/ tensile strength code. We
will use the following example to highlight the additional test requirements.
ASTM D 2000 M 5 BG 407 A14 B14 E014 E034 F17
The test codes are comprised of a suffix letter and two suffix
number combinations, e.g A14.
The suffix letters indicate the property being tested i.e. heat resistance, compression set etc. The first number calls out which ASTM
test method to use and second number indicates the temperature the test should be
conducted under. If the suffix ends in a Z, this indicates there are special testing
requirements called out by the user or third party. Typically, these special
requirements indicate a skewed hardness range, more robust criteria than
outlined in the ASTM test call out, or simply a color change. (Note: the default
color code in the call out will be black.)
The ASTM D2000 is a good gauge to determine the
compatibility of materials and ensure consistency across different manufacturers. However,
care must be taken because ASTM D 2000 does not identify material compatibility
when exposed to aggressive media and environments such as those typically
found in the chemical industry. These applications may typically require thermoplastics which are not addressed by the ASTM D 2000 call out. In addition, care
must also be taken when identifying a particular material, as significant performance
differences exist between different elastomers. For example, NBRs, CRs and
EPDMs have limited performance when compared to high performance elastomers
such as fluroelastomers and perfluroelastomers. Contact your Colonial Seal Co.
at sales@colonialseal.com if youare unsure of the type of material to use for
your seal.
