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The Shull Group |
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53. "Adhesive and Mechanical Properties of Two-Component Latex Films: A Contact Mechanics Approach" Fabbroni, E.F.; Shull, K.R.; Hersam, M.C., J. Polym. Sci. Polym. Phys.. 39, 3090, 2001.
Abstract: We have used a unique approach based on contact mechanics to quantify the adhesive and linear viscoelastic properties of latex films with thicknesses of approximately 100 microns. The latex films are two-component blends made from a combination of a low-Tg latex and a more rigid latex with a Tg close to room temperature. At low volume fractions of the hard particles, the films were very soft and adhesive, as dictated by the properties of the low-Tg matrix material. Adhesive interactions between the film and the indenter enabled us to oscillate the indenter in the direction normal to the film surface while maintaining a constant contact area, allowing us to determine the frequency dependence of the dynamic modulus. The stiffer films with higher volume fractions of hard particles were characterized by indentation measurements, from which we were able to determine the time dependence of the relaxation modulus of the latex films. All results are consistent with a power law form of the relaxation modulus, with an exponent of 0.25. The magnitude of the relaxation modulus increased by a factor of 3000 as the volume fraction of hard particles increases from zero to 0.89.