MIL-DTL-45301E
3.2.3 Backing. Backing shall be made in conformance to the physical properties in table I
and may be either flat or embossed (see 4.6.2).
3.2.4 Vulcanization. The vulcanization time in the creation of specimens shall not exceed
90 minutes at a temperature of 280 degrees Fahrenheit (°F) [137 degrees Celsius (°C)].
Processing instructions and recommended curing time and temperature shall be furnished for class
3, 4, 5, and 6 tread elastomer (see 4.6.3 and 6.2).
3.2.5 Recycled, recovered, or environmentally preferable materials. Recycled, recovered,
or environmentally preferable materials should be used to the maximum extent possible provided
that the material meets or exceeds the operational and maintenance requirements, and promotes
economically advantageous life cycle costs.
3.3 Construction.
3.3.1 Class 1 and class 2. Unless otherwise specified (see 6.2), class 1 and class 2 tread
elastomer shall be supplied with a 0.003 inch (in.) [0.076 millimeter (mm)] minimum layer of
plastic sheet backing (see 3.2.3) on the tread surface with the greatest dimension. When tie gum
is specified (see 6.2), the tread elastomer shall be an assembly consisting of a layer of tread
compound (see 3.2.1), a 0.031 in. (0.787 mm) minimum layer of tie gum on the tread surface with
the greatest dimension (see 3.2.2), and a 0.003 in. (0.076 mm) minimum layer of a plastic sheet
backing on the tie gum (see 3.2.3). The bonding of these materials shall be such that they will not
separate during shipping, normal handling, and processing, including vulcanizing of the tread and
tie gum, if applicable, to the wheels. The bond between the tie gum and tread elastomer must be
not less than 5 pounds per inch [875.6 Newtons per meter (N/m)] of width. Removal or
separation of the plastic backing shall not result in separation of the tie gum from the tread
(see 4.7.1).
3.3.2 Class 3, class 4, class 5, and class 6. Unless otherwise specified (see 6.2), classes 3,
4, 5, and 6 tread elastomer shall be furnished with an anti-stick material either applied to the
elastomer or inserted between the elastomer sheets. This anti-stick material, a coating intended to
be blended into the tread elastomer when milled and extruded, shall not produce any deleterious
changes in the physical properties or performance of the cured tread elastomer. Tread elastomer
shall be capable of being milled and extruded to the required die sizes and cured to meet the
requirements of this specification (see 4.7.2).
3.3.3 Class 4. Class 4 tread elastomer shall be furnished in two unmixed sheets
(sheet 1 and sheet 2) with the reactive agents separated. The two sheets shall be sized so that
equal lengths of sheet, when properly mixed, extruded and cured, shall provide a tread elastomer
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