Orientation Studies of Polyester and Nylon Fibers Containing Crystalline and Amorphous Phases by Means of IR Spectroscopy - 1. Determination of Orientation Coefficients.

The changes in internal orientation occurring in PET and PA6 fibers during their stretching have been analyzed. The evaluation of orientation in both crystalline and noncrystalline polymer has been based on the absorption spectra of the linear polarized IR radiation and on the values of dichroic quotient of absorptive bands taken into consideration. As a direct quantitative measure of orientation, the dichroic orientation coefficient, f//d, has been taken, which results from the general relationships of Hermans-Platzch and Fraser. The application of this coefficient became possible thanks to the preliminary determination by the author of the values of the angles of the transition moment of the absorbing groups taken into consideration, which are present in PET and PA6 macromolecules. The results thus obtained revealed characteristic differences in the course of orientation of structural elements in the crystalline and noncrystalline regions of PET and PA6 fibers during the stretching process. To verify the feasibility of the elaborated spectrometric method, the same specimens have been additionally studied by X-ray and optical polarization methods.