Opto-thermal properties of fibers. XVI. Macrostructural and optical properties of cold-drawn, quenched PET fibers

In this article, the relation between the macrostructural changes in uniaxi ally stretched polyester (PET) fibers, caused by heat treatment, and quench ed in coarse-grain ice were studied. The developing macrostructure was dete rmined using double-beam interferometry. Application was carried out by two -beam interferometry to determine the optical parameters. Using a two-beam Pluta polarizing interference microscope connected to a device to dynamical ly study the draw ratio with birefringence changes. The relations of drawin g changes with some optical parameters are given. The evaluation of density , the mean square density fluctuation, crystallinity, amorphous orientation , crystalline orientation functions, the mean square density fluctuation [e ta(2)], the number of chains per unit volume N-c, and the number of random links between the network junction points N-(1) have been found. The result s obtained clarify the effect of annealing time and temperature with differ ent draw ratios on the structure of PET fibers. Also, the optical results w ere used to calculate an optical orientation function and an optical orient ation angle of drawn, quenched PET fibers. Relations between the optical da ta, draw ratios, and other parameters with different quenching conditions a re given for these fibers. The change of the refractive index profile of th e quenched PET fibers with various conditions are given. Illustrations are given using graphs and microinterferograms. (C) 1999 John Wiley & Sons, Inc . J Appl Polym Sci 72: 1881-1894, 1999.