MEASUREMENT OF THE DEGREE OF DISPERSION OF CARBON BLACK IN POLYETHYLENE USING ABSORPTION OF LIGHT,
BATTELLE MEMORIAL INST COLUMBUS OHIO
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Results indicate that the light transmission through a film of black polyethylene is affected by several variables in addition to dispersion. These include 1 the particle size of the carbon black, 2 the thickness of the film, and 3 the area under examination. The wavelength of light also appears to have some influence on the light absorptivity of polyethylene. The experimental results indicate that the area under examination, i.e., the cross-sectional area of the light beam, has a strong influence on light-transmission values. Variations in transmission are averaged to a greater degree when the area is relatively large. It appears that this averaging of transmission data tends to obscure the desired measurement. The dispersion of carbon black should be a measure of the variation in concentration of the carbon black, on a minute scale, within the polyethylene film. Measurements of light transmission have been made on areas of film of the order of 2 microns in diameter, and it appears that the variations in transmission on this scale are more indicative of the weathering properties than measurements on a larger area. Absorptivity measurements on a number of carbon black-pigmented samples, using both the method prescribed by Federal Specification L-P-590 and the microspectrophotometer technique developed in this work, indicate rather conclusively that the proposed specification will not provide the degree of product control that was intended.
- Physical Chemistry
- Test Facilities, Equipment and Methods