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The self diffusion distributions of viscoelastic molten polyurethanes were determined from the relationship between the relaxation spectra and the distribution of self diffusion. The relaxation spectra of ester, PCL and PCL dyed type molten polyurethanes were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Ree-Eyring and Maxwell non-Newtonian model(REM model) from computer calculation. The experiments were carried out at various temperatures using the physica rheometer with the temperature controller. The self diffusion and hole distance of amorphous region of polyurethane samples were investigated by experiments of stress relaxation. The diffusion coefficients and hole volumes were calculated from rheological parameters and crystallite size in order to study the diffusion of flow segments in amorphous region. It was observed that the relaxation spectra and self diffusions of these polymer samples are directly related to the distribution of molecular weights, viscosities, hole volumes and activation energies of flow segments.

Determination of Self Diffusion Distributions of Molten Polyurethanes by Relaxation Spectra