Effect of winding speed on the physical structure of as‐spun poly(ethylene terephthalate) fibers, including orientation‐induced crystallization

Abstract

SynopsisAs-spun fibers of poly(ethy1ene terephthalate), PET, made at winding speeds ranging from 2000 to 6000 m/min exhibit quite different physical structures. Yarns wound at relatively low speeds are amorphous, whereas those spun at high speeds contain well-developed crystals of closely packed molecules. In this study the structures have been characterized by means of various techniques such as differential scanning calorimetry, x-ray diffraction, density, and pulse propagation measurements. Based on the results obtained, an arrangement of the molecules in the various yarns is proposed. It is shown that these arrangements can account for the extreme wide variety in contraction behavior found experimentally. Finally, the results obtained are compared with those of other investigations into orientation-induced crystallization.

Trans–gauche rotational isomers in partially oriented poly(ethylene terephthalate) fibers

“…(l), valid for samples with cylindrical symmetry, was used'O: (1) where absorbance ( 11 ) and absorbance (1 ) refer to the absorbances of the band with the polarizer parallel (11) and perpendicular (I) to the fiber axis. The absorbances of the trans (973 cm-') and gauche (898 cm-') bands could then be ratioed to the common (632 cm-') band to provide indices of trans and gauche content.…”

Influence of branching on the properties of poly(ethylene terephthalate) fibers

“…1,3 This can be seen, for example, in an increased birefringence. The rise of orientation finally leads to partial crystallization, the formation of a two-phase morphology of highly oriented crystalline areas dispersed in an amorphous, usually less oriented phase.…”

“…where , a , and c are the measured density of the fibers, the density of the amorphous part (1.335 g/cm 3 ), and the density of the crystalline part (1.455 g/cm 3 ), 5 respectively.…”

“…[1][2][3][4][5] Emphasis was on fibers produced with increased wind-up speeds. It is found that with rising wind-up speeds, tenacities and moduli increase and elongations decrease.…”

Kinetics of oriented crystallization of polymers in the linear stress-orientation range in the series expansion approach

“…It has been shown that the effects are controlled by the entropy of deformation and orientation of chain macromolecules in the amorphous component [2,[16][17][18][19][20][21][22][23][24][25]. Oriented crystallization during melt spinning strongly influences the process dynamic and axial profiles of fiber velocity, diameter, tensile stress, birefringence, amorphous and crystalline orientation, degree of crystallinity [4,5,26,27]. The increase in crystallization rate is estimated for several orders of the magnitude in fast melt spinning processes.…”