A-A-52430A
3.2.4 Alternate coating and reinforcement. Unless otherwise specified (see 7.5), coating shall be of sprayable, strippable vinyl material for external pads only. Coating shall be not less than 0.5 mm thick for type I pads and not less than 0.8 mm thick for type II pads. As an alternate reinforcement for type II, class CS and VS pads, pressure sensitive thermosetting adhesive type electrical insulation tape with cotton fabric backing shall be used. Surface coating as specified in 3.2.2 shall be applied.
3.2.5 Dimensions. Pad dimensions shall conform to applicable drawings (see 7.5). Except in restricted locations, minimal thickness of 19 mm shall be maintained.
3.3 Performance.
3.3.1 Bonding. Pads bonded to metal inserts shall withstand temperature range of minus 40 ± 2 degrees Celsius (°C) to plus 70 ± 1°C without bonding separation, embrittlement, or cracking. Force required to separate plies or coatings shall be not less than 2.3 kg per 25.4 mm of width.
3.3.2 Softness. Pads shall conform to softness range specified in table lI. Tests shall be made on finished pad at locations that assure uniformity near edges, as well as at any location of pad, provided periphery of indenter does not extend beyond apex of curvature at edges of pad surfaces.
TABLE II. Loads on 25.4 mm ball to cause indentation of 1/4 of pad thickness.
|
Type |
Temperature (°C) |
Test weight (kg) |
|
I Facial |
+ 21 to + 24 |
2.3 |
|
II Body |
+ 21 to + 24 |
4.5 |
|
I Facial |
-40 to -43 |
13.6 |
|
II Body |
-40 to -43 |
15.9 |
3.3.3 Resistance to extreme temperature. Pads shall evidence no cracks, delaminations, or adhesive failure after 72 hours exposure at 70°C and 72 hours at -40°C.
3.3.4 Fire resistance. Finished pads shall not flame or glow for more than 30 seconds after being subjected to a fire resistance test in accordance with method 5903 of FED-STD-191. Flame and glow time shall be combined to determine conformance to the requirement.
3.3.5 Water absorption. Complete pads shall show no water absorption exceeding 0.5 percent by weigh of finished pad, excluding weight of metal parts. To determine water absorption, three finished pads shall be weighed and immersed in water at 24 ± 3°C with upper surface of each pad approximately 15 mm below surface of water. After 24 hours of immersion, each sample shall be removed, surface dried, and then reweighed. Percentage increase in weight shall be calculated to determine conformance to requirement.
3.3.6 Flexibility. Pads shall not become hard or inflexible due to absorption of sealer, adhesive, or coating and shall evidence no cracking or bond separation. To determine conformance to the requirement, a pad without metal backing shall be bent 60 degrees back and forth around a 25 mm mandrel, completing one cycle in 10 seconds.
3.4 Material safety data sheet (MSDS). If the procuring activity desires a MSDS shall be prepared in accordance with FED-STD-313 (see 7.5).
3.5 Color. Color of exterior surfaces of pads for use inside vehicle shall be black, and finish shall be acceptable from gloss to lusterless. Hatch opening pads and others exposed to exterior view shall be forest green.
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