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Stresses associated with transport in polymeric films
Abstract
The experimental technique of real time holographic interferometry has been developed to measure the transport properties of polymers. The application of holographic interferometry is to measure deformation associated with heat conduction and moisture diffusion. For the heat transfer, a circular disk, an annular disk and a cantilever beam were studied. For the mass transfer, a bi-layer cantilever beam with polyimide films spin-cast on a steel substrate was studied. For the experiment of a clamped disk subjected to a continuous point heating source, the temperature distribution can be obtained on the basis of linear thermoelasticity; thereafter, the corresponding problems of transient thermal stresses and thermal diffusivity can be evaluated. For an isotropic material like PMMA, the holographically recorded fringe pattern is circular. For orthotropic materials, such as wood and liquid crystalline polymers, the fringe pattern is elliptical. Thermal bending experiments associated with heat conduction through the thickness were conducted by using a cantilever beam and an annular disk clamped at the center. The observed deflection was due to a resultant thermal moment induced by a temperature gradient through the thickness. For the experiment of moisture swelling in a bi-layer cantilever beam, the observed deflection was due to a non-uniform distribution of moisture through the thickness. From the transient deflection measured by holographic interferometry, it is shown that the transport properties of thermal diffusivity and mass diffusivity can be obtained by moment analysis. The moment analysis is used to retrieve the thermal diffusivity or mass diffusivity by using the Laplace transform of the governing equations without deriving the analytical solution. The swelling of polymeric films exposed to moisture is a common phenomenon. During this work, the swelling stress and swelling strain associated with moisture diffusion were conducted by a force-strain apparatus which is similar in concept to a Thermomechanical Analyzer. It is shown that the swelling stresses and swelling strains are proportional to the mass uptake, and the diffusion coefficient can be retrieved from the swelling experiment.
Subject Area
Mechanical engineering|Chemical engineering
Recommended Citation
Jou, Chon-Shin, "Stresses associated with transport in polymeric films" (1993). Doctoral Dissertations Available from Proquest. AAI9329635.
https://scholarworks.umass.edu/dissertations/AAI9329635