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Elastomers
| Elastomeric parts have been used in a wide variety of applications
such as; insulating purposes - shock and vibration, or noise reduction
as anti-squeak tape or gaskets, as well as environmental seal applications
in the form of gaskets or seals.
The following standards provide minimum requirements for performance,
safety, and component life, for elastomeric elements used in passenger
rail transit vehicles.
Metal parts to which elastomeric materials are cured shall be made of
SAE J403 hot-rolled steel or equal, suitably cleaned for bonding. Gaskets
shall comply with ASTM D1056. |
| Standard: |
ASTM D2240 - Standard Test
Method for Rubber PropertyDurometer Hardness
| | Purpose: |
This test method describes eight types of rubber hardness measurement
devices known as durometers (AKA Shore): types A, B, C, D, DO, O,
OO and M. The procedure for determining indentation hardness of substances
classified as thermoplastic elastomers, vulcanized (thermoset) rubber,
elastomeric materials, cellular materials, and some plastics is also
described. See excerpt table below.
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| Criteria: |
Specify standard name, Durometer Scale, Rating (please see table
below for common values)
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| Usage: |
Example: ASTM D2240, Durometer Scale A, Hardness 65 (Example is
a typical value for window glazing rubber)
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ASTM D2240, TABLE X1.1 Durometer
Selection: Typical Applications
| Type
(Scale) |
Typical Examples of Materials
Tested |
Durometer Hardness
(Typical Uses) |
| A |
Soft vulcanized rubber, natural rubber, nitriles, thermoplastic
elastomers, flexible polyacrylics and thermosets, wax,
felt, and leathers |
20 to 90 A |
| B |
Moderately hard rubber, thermoplastic elastomers, paper
products, and fibrous materials |
Above 90 A, Below 20 D |
| C |
Medium-hard rubber, thermoplastic elastomers, medium-hard
plastics and thermoplastics |
Above 90 B, Below 20 D |
| D |
Hard rubber, thermoplastic elastomers, harder plastics,
and rigid thermoplastics |
Above 90 A |
| DO |
Moderately hard rubber, thermoplastic elastomers, and
very dense textile windings |
Above 90 C, Below 20 D |
| M |
Thin, irregularly shaped rubber, thermoplastic elastomer,
and plastic specimens |
20 to 85 A |
| O |
Soft rubber, thermoplastic elastomers, very soft plastics
and thermoplastics, medium-density textile windings |
Below 20 DO |
| OO |
Extremely soft rubber, thermoplastic elastomers, sponge,
extremely soft plastics and thermoplastics, foams, low-density
textile windings, human and animal tissue |
Below 20 O |
| CF |
Composite foam materials such as amusement ride safety
cushions, vehicle seats, dashboards, headrests, armrests,
and door panels |
See Test Method F 1957 |
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| Standard: |
ASTM D412 Standard Test Methods for Vulcanized
Rubber and Thermoplastic Rubbers and Thermoplastic Elastomers-Tension
| | Purpose: |
These test methods describe procedures used to evaluate the tensile
(tension) properties of vulcanized rubbers and thermoplastic rubbers
and thermoplastic elastomers. The test methods are not applicable
to ebonite and similar hard, low elongation materials. The test method
used will be dependent upon the Type and Configuration of the material
being tested.
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| Criteria: |
Specify standard name, Desired Tensile Strength, and
Elongation (please see table below for common values) |
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| Usage: |
ASTM D412, Tensile Strength (XX) psi,
Elongation (XX) % Minimum
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| Standard: |
ASTM D1149 Standard Test Method for Rubber
Deterioration-Surface Ozone Cracking in a Chamber
| | Purpose: |
This test method covers the estimation of the resistance
of vulcanized rubber to cracking when exposed to an atmosphere containing
ozone. The rubber specimens are kept under a surface tensile strain,
and the ozone content or partial pressure in the test chamber is maintained
at a fixed value.
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| Criteria: |
Specify standard name, Specimen type A, Test duration,
Ozone concentration, Test temperature, criteria. (Please
see table below for common values)
Note: the test temperature may be increased when end user destination
is in a higher temperature climate.
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| Usage: |
ASTM D1149, Specimen type A, 7 Days, Ozone concentration 100ppm, 104°F, No Cracks
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| Standard: |
ASTM D471 Standard Test Method for Rubber Property-Effect
of Liquids
| | Purpose: |
This test method covers the required procedures to evaluate the
comparative ability of rubber and rubber-like compositions to withstand
the effect of liquids. This test should be used where the elastomer
is likely to come in contact with oils or fuel during it's service
life. The testing oil/fuel is selected based upon the intended application
and exposure oil/fuel. This should be noted in the text with this
specification. The testing time and temperature are given in Table
1, and should be specified based upon application.
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| Criteria: |
Specify standard name, The testing oil/fuel is selection
criteria, time, temperature, and values. (Please see table
below for common values) |
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| Usage: |
ASTM D471, Test oil/fuel representative of application,
(time), (temperature), Maximum change in volume
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| Standard: |
ASTM D395 Standard Test Methods for Rubber Property-Compression
Set
| | Purpose: |
These test methods cover the testing of rubber intended for use
in applications in which the rubber will be subjected to compressive
stresses in air or liquid media. They are applicable particularly
to the rubber used in machinery mountings, vibration dampers, and
seals. The test method A or B shall be selected based upon application,
Test Method A-Compression Set Under Constant Force in Air, Test Method
B-Compression Set Under Constant Deflection in Air.
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| Criteria: |
Specify standard name, maximum deflection (please see
table below for common values) |
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| Usage: |
ASTM D395, Method (A or B),
25% Maximum Set
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| Standard: |
ASTM D624 Standard Test Method for Tear Strength
of Conventional Vulcanized Rubber and Thermoplastic Elastomers
| | Purpose: |
This test method describes procedures for measuring tear strength
of conventional vulcanized thermoset rubber and thermoplastic elastomers.
Several test methods are available, method B is more common for elastomers
in rail vehicle service.
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| Criteria: |
Specify standard name, Test method, tear strength, (please
see table below for common values)
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| Usage: |
ASTM D624, Method (B), (XX)
lbf/in
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| Standard: |
ASTM D746 Standard Test Method for Brittleness
Temperature of Plastics and Elastomers by Impact
| | Purpose: |
This test method covers the determination of the temperature at
which plastics and elastomers exhibit brittle failure under specified
impact conditions. Two test clamp configurations are shown, either
may be selected based upon the material hardness being tested.
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| Criteria: |
Specify standard name, pass/fail temperature (please
see table below for common values)
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| Usage: |
ASTM D746, brittleness temperature
no greater than (XX) degrees F
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| Standard: |
ASTM D573 Standard Test Method for Rubber-Deterioration
in an Air Oven
| | Purpose: |
This test method describes a procedure to determine the influence
of elevated temperature on the physical properties of vulcanized rubber.
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| Criteria: |
Specify standard name, Time, temperature, material property
change permissible (please see table below for common values) |
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| Usage: |
ASTM D573, (XX) Hours, (XX)°F,
% change in property
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| Standard: |
ASTM D1055 Standard Specifications
for Flexible Cellular Materials-Latex Foam
| | Purpose: |
These specifications, including test methods, apply to flexible
cellular rubber products known as latex foam rubbers but do not
apply to sponge and expanded rubbers. This standard covers a variety
of physical properties that can be specified in detail using the
standards numbering system.
In general, this standard is typically quoted for foam tolerances,
with the remaining properties to be determined during design.
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| Criteria: |
For Foam Tolerances: Specify standard name, reference table
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| Usage: |
ASTM D1055, Table 2, for foam in general applications, Table 3,
for foam in special applications (tables are similar)
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| Standard: |
ASTM D1056 Standard Specification for
Flexible Cellular Materials-Sponge or Expanded Rubber
| | Purpose: |
This specification covers flexible cellular rubber products known
as sponge rubbers and expanded rubbers but does not apply to latex
foam rubbers. The base material used in their manufacture may be natural
rubber, reclaimed rubber, synthetic rubber or rubber-like materials,
alone or in combination. Ebonite cellular rubbers are not included.
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| Criteria: |
ASTM D1056 is a specification with minimum
requirements listed to meet this standard per rubber type.
Note: the component designer must determine the rubber type based
upon the design requirements.
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| Usage: |
... Shall meet the requirements of ASTM 1056
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Elastomeric Material Common Usage Table
| Physical Property |
ASTM Test Method |
Test Value |
| Hardness, Durometer A |
D2240 |
45 to 75 |
| Tensile strength |
D412 |
1500 psi |
| Ultimate elongation |
D412 |
300%, min |
| Ozone resistance |
D1149, Type A, 7 Days, Ozone concentration 100ppm, 104 degrees
F |
No cracks under 7x magnification |
| Oil aging resistance |
D471, Test oil/fuel shall be representative of application,72
hours, 158 degrees F |
+30% maximum change in volume |
| Permanent-set resistance |
D395, Method A or B |
25% Maximum Set |
| Tear resistance |
D624, Method B |
300 lb/in |
| Brittleness temperature |
D746 |
brittleness temperature no greater than -40°F |
| Resistance to heat aging |
D573, 72 hours, 158°F |
-30% change in elongation
-15% change in tensile strength
-5 to +15 change in hardness |
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