Document Type
Thesis
Date of Award
12-31-1960
Degree Name
Master of Science in Chemical Engineering - (M.S.)
Department
Chemical Engineering
First Advisor
Michael Frederick
Second Advisor
Jerome J. Salamone
Third Advisor
Saul I. Kreps
Abstract
Optical properties of pigmented films such as hiding power, scattering coefficient, and absorption coefficient were measured at three bands of wavelength of light (blue, green, red) for ten white pigments at seven pigment concentrations in a paint. These pigments range from the highest index of refraction (rutile) to the very low index of an extender pigment (CaC031); they range from a fine particle size (average 0.2 microns) to a relatively coarse size (average 2.2 microns).
Among the findings presented below the first two confirm the general observations of pigment behavior found by others; the rest of the findings are new.
1. Hiding power and scattering coefficients increase with concentration and index of refraction.
2. Curves of both hiding power and scattering coefficient versus concentration for the three bands of wavelength of light are generally similar, except that the magnitude of the values for the shorter wavelengths is greater than the values for the longer wavelengths due to the variation of index of refraction with wavelength.
3. For pigments with equal index of refraction a coarse particle size favors the development of high strength at high concentrations; a fine particle size favors development of high strength at low concentrations.
4. The change in scattering coefficient with concentration is linear up to a particular limiting concentration for each pigment. The greater the particle size the higher the concentration at which linearity ceases and the higher the concentration for which a maximum in the curve is reached.
5. The point of departure from linearity was found to be that concentration at which each pigment has the same edge-to-edge separation between particles. This separation is nearly one-hRlf the wavelength of the incident light and is also approximately equal to the separation of point objects in the theoretical equation for the resolving power of optical instruments.
6. The absorption coefficient for all pigments studied increases in a linear manner with. concentration.
An empirical equation was derived which predicts the change in scattering coefficient with a change in particle size (monodispersed particles) at any given wavelength of incident light and relative index of refraction when the pigment concentration is between 5-15% by volume.
This equation was expanded to successfully predict scattering coefficients over a range of pigment concentrations from a knowledge of the particle size distribution (polydispersed particles), index of refraction, concentration, and wavelength of incident light.
Recommended Citation
Mitton, Parker Bovaird, "Hiding power of white pigments : theory and measurement" (1960). Theses. 3010.
https://digitalcommons.njit.edu/theses/3010
