USING DYE CARRIERS AS STRUCTURAL PROBES (POLYESTER, CRYSTALLIZATION)

When polyester is annealed at low temperatures, or drawn at low spinning speeds, chain folding predominates and crystallization is delayed. At high annealing temperatures or high draw ratios, crystallization occurs rapidly. A critical annealing temperature range has been identified between 180(DEGREES)C and 200(DEGREES)C. As annealing temperature increases up to 180(DEGREES)C, the number of crystallites increases. In the critical temperature range, the crystallites are numerous and small. They effectively act as crosslinks stabilizing the structure and limiting dye uptake. Above the critical range, crystals grow in size and perfection at the expense of the microcrystals. Void space is created in this way permitting segmental motion of the chains and an increase in dye uptake.; In this study, the chemical energy of the dye carrier 1,2,4-trichlorobenzene was used to probe the structural changes in polyester fiber. Woven polyester fabric was dyed using a disperse dye.; Using a dyeing procedure at constant time (90 minutes) and temperature (100(DEGREES)C), the effects of the concentration of carrier in the bath were shown. As carrier concentration increased at low concentrations, dye uptake increased. The chemical energy available from the carrier promoted polymer chain folding. Chain folding continued with increasing carrier concentration until at a critical concentration of carrier, a network of small, numerous microcrystals was formed effectively crosslinking the polymer. In this region, the void space necessary for dye penetration was minimum. This appeared as a minimum in dye uptake. As carrier concentration was increased beyond this region, crystal growth was promoted. Using the increasing chemical energy of the carrier, crystals grew in size and perfection at the expense of the microcrystals. Void space created in this way permitted segmental motion of the polymer chains which was shown as an increase in dye uptake.; In this study, two minima in dye uptake were noted corresponding to: (1) a carrier concentration of 4% for the 90 minute dyeing time, and (2) a 12% carrier concentration for a 30 minute dyeing time. The higher concentration of dye carrier corresponded to a higher level of chemical energy resulting in a downward shift in the minimum on the time scale.