MIL-T-68410
4.6.7.1.3 0evice for application of tape. The device for application of the tape for test purposes shall consist of a horizontally mounted, free turning, rubber-coated roller with the following dimensions:
Total weight4.55 +0.1 pounds Width 2.5 +0.1 inches Diameter 3.25 +0.1 inches
The roller shall be faced with 1/4 inch of rubber with a Shore Durometer hardness of 75 +5. The roller shall be propelled lengthwise back and forth over the tape in such a manner that only the weight of the roller rests on the tape, and at the rate of 12 inches per minute. The device can be either manually or mechanically operated. The adhesive side of the tape shall not be touched during application. For referee purposes, the device shall be mechanically operated.
4.6.7.2 Procedure. The flanged surface shall be polished lengthwise with 240 or 280 grit dry silicon carbide or aluminum oxide cloth or paper, and cleaned with solvent conforming to TT-T-291, grade 1. Approximately 25 grams of dry 8-mesh calcium chloride in a nonwoven porous cloth bag, or equivalent, shall be weighted to the third decimal place and inserted into the test cup. The bag of calcium chloride should be weighted in a closed container. The cup shall be positioned in a jig to support the flange, and a tape specimen 2 inches wide and longer than the test dish shall be rapidly and lightly applied. The
tape shall then be trimmed to the edge of the dish. Final application shall be accomplished by rolling the tape application device once back and forth over the tape in the lengthwise direction. The assembly shall be placed for 15 minutes in a desiccator at standard temperature, and then removed from the desiccator and placed in the humidity cabinet. After 72 hours it shall be removed from the humidity cabinet and placed for 15 minutes in a desiccator at standard temperature. The cloth bag of calcium chloride shall then be removed from the assembly, immediately placed in the weighing container and weighted on analytical balance.
4.6.7.3 Calculation (WVTR) The water vapor transmission shall be report in grams of water vapor transmitted per 100 sq inches of tape area for 24 hours, and still be calculated as follows:
(W2 - W1) x 2400
Water vapor transmission rate (WVTR) = T x A
Where: W1 = weight (in grams) before exposure period
W2 = weight (in grams) after exposure period
T = exposure period (in hours)
A = area (in sq inches) of opening in dish (normally 4 sq inches)
A minimum of three tests shall be made and the average of all tests on a sample shall be reported.
5. PACKAGING
5.1 Preservation and packing . Preservation and packing shall be level A, or C as specified (See 6.2).
5.1.1 Level A.
5.1.1.1 Tape. Unless otherwise specified, the tape shall be wound in rolls (see 3.4). Each roll shall be wrapped in heavy kraft paper conforming to UU-P-268, and sealed with paper tape conforming to PPP-T-45.
5.1.1.2 Sheets. Unless otherwise specified, sheet shall be interleaved with any suitable paper extending over the full area of contact between sheets. The sheets shall not exceed 10 inches in height when stacked.
5.1.2 Level C. Tape and sheet shall be preserved and packaged to afford protection against deterioration and damage.
5.1.3 The tape and sheet shall be not more than three quarters of a year old from date of manufacture to date of delivery for use in military aircraft or equipment.
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