Deformation of undrawn poly(trimethylene terephthalate) (PTT) fibers

Fibers were obtained by melt spinning of poly(trimethylene terephthalate) with take-up velocities ranging from 500 to 5000 m/min. Deformation behavior was analyzed with the use of a thermo-mechanical analyzer (TMA). Constant force and isostrain experiments were done. The structure of undrawn fibers was analyzed by optical birefringence, density, wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). x thermo-mechanical behavior — spontaneous elongation of some samples, thermal shrinkage of others, maxima of shrinkage vs. spinning speed — can be explained by the initial structure of fibers and structural processes accompanying deformation. With increasing take-up speed, molecular orientation and crystallinity of fibers increase. The fibers differ also in their ability to crystallize. Initially amorphous (low-speed-spun) fibers crystallize when heated above glass transition temperature. This effect (“cold crystallization”) has been observed in DSC.