THE MICROSTRUCTURE AND MACROSTRUCTURE OF SULFONATED POLY(ETHYLENE TERETHPHALATE) FIBERS

The effects of fiber-forming processes on the microstructure and macrostructure and overall orientation in sulfonated poly(ethylene terephthalate) (SPET) fibers are reported. The processing parameters examined include drawing, crimping, relaxing, and annealing. Drawing and annealing cause changes in both the crystalline structure and molecular packing in the noncrystalline regions, while crimping and relaxing appear to affect only the non-crystalline regions. A bimodal melting endotherm was observed for the SPET fibers. Experimental data suggest the low-temperature endotherm of the SPET fibers originates from melting of the crystalline structure formed on drawing, and that the high-temperature endotherm results from melting the heat-induced crystals formed during fiber processing and/or thermal analysis. Compared to the PET fibers, the SPET chains in the undrawn fibers appear to have higher mobility, are easier to crystallize, and form smaller crystals upon drawing as well as DTA heating. At the crimped stage, the SPET fibers have higher overall molecular packing but lower overall orientation than the PET fibers. The differences in physical and thermal properties between the analogous SPET and PET fibers are related to their different responses to processing variations because of molecular weight and side-group effects. (C) 1993 John Wiley & Sons, Inc.