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Tyco Electronics Corporation
300 Constitutional Drive
Menlo Park, CA 94025 USA
Specification
This Issue:
Date:
Replaces:
RT-1321
Issue 3
December 1, 1981
Issue 2
THERMOFIT® ELASTOMERIC POLYMER BLEND MOLDED COMPONENTS
Flame Resistant, Flexible, Heat-Shrinkable
1. SCOPE
This specification covers the requirements for one type of flexible, electrical insulating molded component
whose expanded dimensions will reduce to a predetermined size upon the application of heat in excess of
175°C (347°F).
2. APPLICABLE DOCUMENTS
This specification takes precedence over documents referenced herein. Unless otherwise specified, the latest
issue of referenced documents applies. The following documents form a part of this specification to the
extent specified herein.
2.1 GOVERNMENT-FURNISHED DOCUMENTS
Federal
P-C-437 Cleaning Compound, High Pressure (Steam) Cleaner
Military
MIL-G-3056 Gasoline, Automotive, Combat
MIL-H-6083 Hydraulic Fluid, Petroleum Base, for Preservation and Operation
MIL-L-7808 Lubricating Oil, Aircraft Turbine Engine, Synthetic Base
MIL-F-46172 Fuel, Diesel, Referee Grade
MIL-H-46170 Hydraulic Fluid, Rust Inhibited Fire Resistant, Synthetic Hydrocarbon Base
MIL-STD-105 Sampling Procedures and Tables for Inspection by Attributes
2.2 OTHER PUBLICATIONS
American Society for Testing and Materials (ASTM)
D 149 Standard Methods of Tests for Dielectric Breakdown Voltage and Dielectric Strength of
Electrical Insulating Materials at Commercial Power Frequencies
D 257 Standard Methods of Test for D-C Resistance or Conductance of Insulating Materials
D 412 Standard Method of Tests for Rubber Properties in Tension
D 570 Standard Methods of Test for Water Absorption of Plastics
D 635 Standard Methods of Test for Rate of Burning and/or Extent and Time of Burning of Self-
Supporting Plastics in a Horizontal Position
D 792 Standard Methods of Test for Specific Gravity and Density of Plastics by Displacement
D 2240 Standard Method of Tests for Rubber Property -- Durometer Hardness
D 2671 Standard Methods of Testing Heat Shrinkable Tubing for Electrical Use
G 21 Recommended Practice for Determining Resistance of Synthetic Polymeric Materials to
Fungi
Page 2 SPECIFICATION RT-1321 ISSUE 3
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(Copies of ASTM Publications may be obtained form the American Society for Testing and Materials, 1916
Race Street, Philadelphia, Pennsylvania 19103.)
3. REQUIREMENTS
3.1 MATERIAL
The molded components shall be fabricated from a crosslinked, thermally stabilized, flame-retsistant ,
modified elastomeric polymer blend. They shall be homogeneous and essentially free from flaws, defects,
pinholes, bubbles, seams, cracks, and inclusions.
3.2 COLOR
The molded components shall be black.
3.3 PROPERTIES
The molded components and the material from which they are fabricated shall meet the requirements of
Table 1.
4. QUALITY ASSURANCE PROVISIONS
4.1 CLASSIFICATION OF TESTS
4.1.1 Qualification Tests
Qualification tests are those performed on molded slabs and components submitted for qualification as
satisfactory products and shall consist of all tests listed in this specification.
4.1.2 Acceptance Tests
Acceptance tests are those performed on molded slabs and components submitted for acceptance under
contract. Acceptance tests shall consist of the following: dimensions, dimensional recovery, tensile strength,
ultimate elongation, heat shock, and flammability.
4.2 SAMPLING INSTRUCTIONS
4.2.1 Qualification Test Samples
Qualification test samples shall consist of six molded slabs, 6 x 6 x 0.075 ± 0.010 inches
(152 x 152 x 1.9 ± .25 mm) and the number of molded components specified. The molded slabs shall be
fabricated from the same lot of material and shall be subjected to the same degree of crosslinking as the
molded components.
4.2.2 Acceptance Test Samples
Acceptance test samples shall consist of specimens cut from a molded slab 6 x 6 x 0.075 ± 0.010 inches (152
x 152 x 1.9 ± .25 mm), and molded components selected at random in accordance with MIL-STD-105,
inspection Level S-2, AQL 6.5 percent. The molded slab shall be fabricated from the same lot of material
and shall be subjected to the same degree of crosslinking as the molded components. A lot of components
shall consist of all molded components from the same lot of material, from the same production run, and
offered for inspection at the same time.
SPECIFICATION RT-1321 ISSUE 3 Page 3
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4.3 TEST PROCEDURES
4.3.1 Dimensional Recovery
Samples of molded components, as supplied, shall be measured for dimensions in accordance with ASTM D
2671. The samples then shall be conditioned for 10 minutes in a 175 ± 2°C (347 ± 4°F) oven, or equivalent,
cooled to room temperature and remeasured.
4.3.2 Elastic Memory
A 6 x 1/8-inch (152 x 3.2-mm) specimen cut from a molded slab shall be marked with two parallel gauge
lines 1 inch (25 mm) apart in the central portion of the specimen. The distance between gauge lines shall be
recorded as the original length. A 2-inch (51-mm) portion of the specimen including both gauge lines then
shall be heated for 5 minutes in a 175 ± 2°C (347 ± 4°F) oven, or equivalent, removed from the oven and
stretched within 10 seconds, until the gauge lines are 4 inches (102 mm) apart. The extended specimen shall
be cooled to room temperature and released from tension. After 24 hours at room temperature, the distance
between the gauge lines shall be measured and recorded as the extended length. The portion of the specimen
including both gauge lines then shall be reheated for 5 minutes in a 175 ± 2°C (347 ± 4°F) oven, or
equivalent, and the distance between gauge lines then shall be measured and recorded as the retracted length.
Expansion and retraction shall be calculated as follows:
E = Le - Lo
Lo x 100
R = Le - Lr
Le - Lo x 100
Where: E = Expansion (percent)
R = Retraction (percent)
Lo = Original Length [inches (mm)]
Le = Extended Length [inches (mm)]
Lr = Retracted Length [inches (mm)]
4.3.3 Tensile Strength, Tensile Stress and Ultimate Elongation
Three specimens cut from a molded slab using Die D of ASTM D 412 shall be tested for tensile strength,
tensile stress and ultimate elongation in accordance with ASTM D 412.
4.3.4 Low Temperature Flexibility
Three 6 x 1/4-inch (152 x 6.3-mm) specimens cut from a molded slab shall be conditioned, along with a 3/8-
inch (9.5-mm) mandrel, in a cold chamber at -55 ± 3°C (-67± 5°F) for 4 hours. After completion of the
conditioning, and while still in the cold chamber, each specimen shall be bent around the mandrel through
not less than 360 degrees within 10 ± 2 seconds. The specimens then shall be visually examined for cracks.
4.3.5 Heat Shock
Three 6 x 1/4-inch (152 x 6.3-mm) specimens cut from a molded slab shall be conditioned for 4 hours in a
200± 5°C (392 ± 9°F) mechanical convection oven with an air velocity of from 100 to
200 feet per minute past the specimens. After conditioning, the specimens shall be removed from the oven,
cooled to room temperature, and bent through 360 degrees over a 3/8-inch (9.5-mm) diameter mandrel. The
specimens then shall be visually examined for evidence of dripping, flowing or cracking.
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4.3.6 Heat Aging
Three specimens, prepared and measured in accordance with 4.3.3 shall be conditioned for
168 hours in a 121 ± 3°C (250 ± 9°F) mechanical convection oven with an air velocity of 100 to
200 feet per minute past the specimens. After conditioning, the specimens shall be removed from the oven,
cooled to room temperature, and tested for tensile strength and ultimate elongation in accordance with 4.3.3.
4.3.7 Fluid Resistance
Six specimens prepared and measured in accordance with 4.3.3 shall be completely immersed in each of the
test fluids listed in Table 1 for 24 hours at the temperature specified. The volume of the fluid shall be not
less than 20 times that of the specimens. After conditioning, the specimens shall be lightly wiped and then
air-dried for 30 to 60 minutes at 23 ± 3°C (73 ± 4°F) . The three specimens intended for the tensile strength
and elongation tests shall then be tested for tensile strength and ultimate elongation in accordance with 4.3.3.
The other three specimens shall be weighed before and after immersion and the weight change calculated as
a percent.
4.4 REJECTION AND RETEST
Failure of any sample to comply with any one of the requirements of this specification shall be cause for
rejection of the lot represented. Material which has been rejected may be replaced or reworked to correct the
defect and them resubmitted for acceptance. Before resubmitting, full particulars concerning the rejection
and the action taken to correct the defect shall be furnished to the inspector.
5. PREPARATION FOR DELIVERY
5.1 PACKAGING
Packaging of molded components shall be in accordance with good commercial practice. The shipping
container shall be not less than 125 pound test fiberboard.
5.2 MARKING
Each molded component shall be distinctly identified on the part and/or package with the manufacturing
name or symbol, the manufacturer’s part number, lot number, date of manufacture, and use before date.
SPECIFICATION RT-1321 ISSUE 3 Page 5
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TABLE 1
Requirements
PROPERTY UNIT REQUIREMENTS TEST METHOD
PHYSICAL
Dimensions
Inches (mm)
In accordance with applicable
specification control drawing
Section 4.3.1
ASTM D 2671
Dimensional Recovery Inches (mm) In accordance with applicable
specification control drawing
Elastic Memory Percent 200 minimum expansion
90 minimum retraction Section 4.3.2
Tensile Strength psi (MPa) 1500 minimum (10.3) Section 4.3.3
Tensile Stress psi (MPa) 1200 maximum(8.3) Section 4.3.3
Ultimate Elongation Percent 300 minimum ASTM D 412
Specific Gravity --- 1.6 maximum ASTM D 792
Hardness Shore A 85 + 10 ASTM D 2240
Low Temperature Flexibility
4 hours at -55°C (-67°F) No cracking Section 4.3.4
Heat Shock
4 hours at 200°C (392°F) --- No dripping, flowing or cracking Section 4.3.5
Heat Aging
168 hours at 121°C (250°F)
Followed by tests for:
--- --- Section 4.3.6
Tensile Strength psi (MPa) 1200 minimum (8.3) Section 4.3.3
Elongation Percent 250 minimum
ELECTRICAL
Dielectric Strength
Volts/mil
(kV/mm)
200 minimum (7.9)
ASTM D 149
Volume Resistivity ohm-cm 1010 minimum ASTM D 257
CHEMICAL
Flammability
Average Time of Burning
Seconds
120 maximum
ASTM D 635
Average Extent of Burning Inches (mm) 1.0 maximum (25)
Fungus Resistance --- Rating of 1 or less ASTM G 21
Water Absorption
24 hours at 23°C (73°F) Percent 1.0 maximum ASTM D 570
Fluid Resistance
24 hours at 25 ± 3°C (77 ± 5°F) in:
Lubricating Oil (MIL-L-7808)
Diesel Oil (MIL-F-46462)
--- --- Section 4.3.7
Water
Followed by tests for:
Tensile Strength psi (MPa) 1000 minimum (6.9) Section 4.3.3
Ultimate Elongation percent 225 minimum
Weight Increase percent 10 maximum Section 4.3.7
Page 6 SPECIFICATION RT-1321 ISSUE 3
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TABLE 1
Requirements
CHEMICAL (Continued)
Fluid Resistance
24 hours at 25 ± 3°C (77 ± 5°F) in:
Gasoline Automotive (MIL-G-3056)
Followed by tests for:
--- --- Section 4.3.7
Tensile Strength psi (MPa) 800 minimum (5.5) Section 4.3.3
Ultimate Elongation percent 225 minimum
Weight Increase percent 25 maximum Section 4.3.7
Fluid Resistance
24 hours at 25 ± 3°C (77 ± 5°F) in:
Isopropyl Alcohol
Cleaning Fluid (P-C-437)
Followed by tests for:
--- --- Section 4.3.7
Tensile Strength psi (MPa) 1400 minimum (9.7) Section 4.3.3
Ultimate Elongation percent 225 minimum
Weight Increase percent 10 maximum Section 4.3.7
Fluid Resistance
24 hours at 71 ± 3°C (160 ± 5°F) in:
Hydraulic Fluid (MIL-H-6083)
Hydraulic Fluid (MIL-H-46170)
--- --- Section 4.3.7
Followed by tests for:
Tensile Strength psi (MPa) 1000 minimum (6.9) Section 4.3.3
Ultimate Elongation percent 225 minimum
Weight Increase percent 25 maximum Section 4.3.7
