MIL-DTL-11891G(AT)
3.3.4.9.1 Specimen preparation. The size of the specimens shall be in accordance with
procedure B of ASTM D518, except the thickness shall be 0.080 + 0.005 inch. Specimens shall
be obtained from either of the following:
a. Three specimens shall be taken from the track block chevron and shall not include
any outer surface.
b. Three specimens shall be taken from production molding blanks of uncured rubber
compounds, being used to rubberize track components, prepared in the form of
ASTM tensile slabs and certified as being of an equivalent state of cure as the
production molding.
3.3.4.9.2 Procedure. The specimen shall be tested in accordance with procedure B of
ASTM D518, except the length of the clamping strips shall be such as to facilitate placement
within the ozone chamber. Specimens shall then be placed in the chamber and exposed for 7 days
at a temperature of 100 + 2°F in an air-ozone mixture containing 50 + 5 parts by volume of ozone
per hundred million parts of air. The specimen surfaces shall be finished smoothly and of uniform
thickness in accordance with part C of ASTM method D-15. The rubber materials shall have no
evidence of cracks when inspected at 7 power magnification at the end of 7 days.
3.3.4.10 Brittleness point of flexible polymers. The specimens and test method shall be in
accordance with ASTM D2137. Specimens shall be type B of method A and tested at a
temperature of -40 + 3.6°F in accordance with method A of ASTM D2137. Five specimens shall
be tested and inspected showing no evidence of cracks, fissures, or pinholes. In the event one
specimen fails, an additional five specimens shall be prepared and tested. Failure of two or more
of the initial five specimens, or any of the last five specimens, shall be cause for rejection. Test
results shall be reported to the Government (see 4.7.2.12).
3.3.4.11 GC mass spec. The Government may perform spot inspections for the purpose
of obtaining samples for pyrolysis-gas chromatography/mass spectrometry analysis. Up to five
samples may be taken at any time during a production contract. Samples will be taken from end
item cured parts. The initial part of the method will thermally desorb the additives, which are then
analyzed by gas chromatography/mass spectrometry. Following desorption of the additives the
remaining sample will be pyrolyzed and analyzed by gas chromatography/mass spectrometry. A
baseline scan will be performed on the material submitted for qualification. Future results will be
compared with the baseline to determine that there are no new peaks appearing, no ingredients
missing, and no substitutions in subsequent production runs (see 4.7.2.13).
3.3.4.12 Track blowout test. This test is required for compounds being submitted for
qualification for integral pad track systems using the T107 track as the candidate qualification
design. Testing shall be conducted at the U.S. Army Tank-automotive and Armaments Command
and arrangements can be made by contacting the preparing activity. Testing will be conducted on
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