Changes In Film Density Research Articles

Observations on the coefficient of friction of polypropylene film

AbstractData are presented relating the time change of the coefficient of friction of cast polypropylene films to changes in film density and concentration of surface lubricant. It is shown that during aging the density of polypropylene increases, thus causing a decrease in the friction coefficient. It is also shown that although the lubricant added to the polymer will diffuse to the surface of copolymer films, no diffusion occurred in polypropylene films.

The Determination of the Optimum Density and the Density-Range of Radiographs from Visual Effects

Minimum perceptible change in film-density or contrast ΔDmin were calculated for several factors from an empirical formula of vision utilized in illuminating engineering. These agreed with experimental results. Physiological contrast was quantitized as the ratio of film-gamma to ΔDmin. The optimum densities for several factors were obtained from the maxima of the ratios. The optimum density-ranges were obtained from graphs of above ratios to logarithmic exposure. If the density-range produced by in thickness takes a maximum. The exposure-factors of such a radiograph were explained to be the optimum.

Physico-Chemical Studies on the Mechanism of the Drying of Linseed Oil I—Changes in Density of Films

Physico-Chemical Studies on the Mechanism of the Drying of Linseed Oil I—Changes in Density of Films