MIL-P-8587 Plastic; Sheet, Colored, Instrument Flying Training

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MIL-P-85878

4.7 Test methods.

4.7.1 Spectral transmittance.  The measurement of spectral transmittance shall be conducted by means of a recording spectrophotometer, utilizing a double monochromator having a band width of 10 millimicrons. The photometric balance shall be achieved by photoelectric control operating from an integrating sphere which receives the sample beam alternately. The total spectral transmittance at any wavelength shall be determined with the specimen in position against the sphere wall and with identical reflectors (magnesium oxide or magnesium carbonate) at the sample and standard reflectance apertures. Precautions shall be taken to insure the proper adjustment of the 100-percent photometric balance, accurate wavelength and photometric calibration, and proper alignment of the record chart. Values below 1 percent will be regarded as 0.0 percent for  purposes  of  computation.  In  case  of  dispute,  referee  tests  will  be  conducted  on  a  General  Electric recording spectrophotometer, or equal, all measurement being made on the 100 percent cam.

4.7.2 Color stability.  After 60 hours' exposure to a carbon arc of the fadeometer type, enclosed in a corex D globe, the plastic shall be tested for conformance to the three colorimetric requirements. The arc shall carry approximately 13 amperes and one of the electrodes shall be cored. The specimen shall be approximately 15 inches  (38.1 cm) from the light source. The temperature of the specimen shall not exceed 131°F  (55°C) during the test.

4.7.3 Light transmittance.  The total visible light transmittance shall be computed from the spectral data for the visual response of the I.C.I standard observer and illuminate "C". The sum of the transmittance values of 1 percent, or more, at each of the wavelengths in table VI shall be multiplied by 0.0333 to yield the light transmittance.

TABLE VI. Wavelengths

4.7.4 Total spectral transmittance. The total spectral transmittance., measured as specified in 4.7.1, shall be obtained throughout the wavelength ranges specified. The values shall be determined with the 100 percent cam in position.

4.7.5 Diffuse spectral transmittance. The same area of the specimen shall be used for this measurement as was used for the total spectral transmittance determination. Diffuse spectral transmittance shall be obtained by means of the procedure specified inn 4.7.1, modified as follows: The magnesium oxide or magnesium carbonate reflector at the reflectance sample aperture shall be replaced by an absorber. This absorber shall have a reflectance of 0.5 percent, or less at the wavelengths at which diffuse spectral transmittance is determined. The aperture at the absorber shall be 1-1/4 inches in diameter. It is recognized that the light scattered at very small angles from the direct beam is not included in this determination.

4.7.6 Minor optical defects.  The existence of minor optical defects shall be determined in accordance with ASTM  D637.  Minor  defects  shall  include  any  embedded  particles,  bubbles,  or  scratches  which  reduce visibility through the plastic and those localized imperfections which cause a variation in angular deviations of more than 5 minutes within a distance of not more than 20 inches of the screen specified in ASTM D637. It is not required to qualitatively survey the sheet for such variation in deviation, but localized imperfections which

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