Rapid mechanical deformation of poly(ethylene terephthalate) fibers at temperatures above the glass transition

J of Applied Polymer Sci

2001

ABSTRACT:The superstructure and mechanical properties of poly(ethylene terephthalate) fibers zone-drawn under a critical necking tension ( c ) were studied. c was defined as the minimum tension needed to generate a neck at a given drawing temperature (T d ) and was measured over a temperature range of 70 -120°C. The c value increased rapidly with decreasing T d in the temperature range below 85°C, but the temperature dependence of c was small above 85°C. The neck profile relied on T d , becoming more shapely with decreasing T d . A neck with a gradual decrease in diameter was observed in the fibers drawn at 100°C and above. The draw ratio increased significantly with increasing T d above 90°C, but birefringence decreased. Density decreased gradually with increasing T d , and fiber drawn at 120°C had a density of 1.347 g/cc. Wide-angle X-ray diffraction photographs of the fibers drawn at 100°C and below showed reflections due to crystallites, but a photograph of the fiber obtained at 120°C showed a ring-like amorphous halo. The storage modulus (EЈ) at 25°C increased progressively with decreasing T d , and the fiber drawn at 70°C had the maximum EЈ value among the fibers drawn at a series of T d 's.

Section: Introductionmentioning

confidence: 99%

“…In the drawing processes of many polymers, necking is induced in a very narrow temperature range close to the glass‐transition temperature ( T g ) and plays an important role in the production of polymers with high moduli and high strength. Necking in amorphous and semicrystalline polymers has been studied extensively 1–6…”

Section: Introductionmentioning

confidence: 99%

Superstructure and mechanical properties of poly(ethylene terephthalate) fibers zone‐drawn under critical necking tension

J of Applied Polymer Sci

2001

“…The relationships of neck geometry and neck propagation to the stress, strain, and strain rate have been studied extensively. [1][2][3][4][5][6] Structural changes such as molecular orientation, strain-induced crystallization, lamellar unfolding, and molecular slippage occur simultaneously in the neck zone. The superstructure formed by the neck af-fects various properties of the fibers finally obtained.…”

Section: Introductionmentioning

confidence: 99%

Changes in superstructure and mechanical properties of poly(ethylene‐2,6‐naphthalate) fibers with critical necking tension

J. Polym. Sci. B Polym. Phys.

Hasegawa

2001

Poly(ethylene-2,6-naphthalate) fibers were zone-drawn under a critical necking tension ( c ) defined as the minimum tension needed to generate a necking at a given drawing temperature (T d ). In the zone drawing under c , the neck was observed from 110 to 160°C. The superstructure in a neck zone induced at each T d was studied. The c value decreased exponentially with increasing T d and dropped to a low level at a higher T d . The draw ratio increased rapidly with T d increasing above 90°C, but the birefringence and degree of crystallinity decreased gradually. To study the molecular orientation in the neck zone, we measured a dichroic ratio (A P /A Ќ ) of a COO band at 1256 cm Ϫ1 along a drawing direction in the neck zone with a Fourier transform infrared microscope. A P /A Ќ at T d ϭ 110°C increased rapidly in the narrow neck zone, and that at T d ϭ 140°C increased in the edge of the wide neck zone. Wide-angle X-ray diffraction patterns of the fibers obtained at T d ϭ 130°C and lower showed three reflections due to an ␣ form, but those at T d ϭ 140 and 150°C had reflections due to the ␣ form and a ␤ form.

“…The relationships of neck geometry and neck propagation to the stress, strain, and strain rate have been studied extensively 1–6. Structural changes such as molecular orientation, strain‐induced crystallization, lamellar unfolding, and molecular slippage occur simultaneously in the neck zone.…”

Section: Introductionmentioning

confidence: 99%

Changes in superstructure and mechanical properties of poly(ethylene‐2,6‐naphthalate) fibers with critical necking tension

J Polym Sci B Polym Phys

Hasegawa

2001

Poly(ethylene‐2,6‐naphthalate) fibers were zone‐drawn under a critical necking tension (σc) defined as the minimum tension needed to generate a necking at a given drawing temperature (Td). In the zone drawing under σc, the neck was observed from 110 to 160 °C. The superstructure in a neck zone induced at each Td was studied. The σc value decreased exponentially with increasing Td and dropped to a low level at a higher Td. The draw ratio increased rapidly with Td increasing above 90 °C, but the birefringence and degree of crystallinity decreased gradually. To study the molecular orientation in the neck zone, we measured a dichroic ratio (A‖/A⟂) of a CO band at 1256 cm−1 along a drawing direction in the neck zone with a Fourier transform infrared microscope. A‖/A⟂ at Td = 110 °C increased rapidly in the narrow neck zone, and that at Td = 140 °C increased in the edge of the wide neck zone. Wide‐angle X‐ray diffraction patterns of the fibers obtained at Td = 130 °C and lower showed three reflections due to an α form, but those at Td = 140 and 150 °C had reflections due to the α form and a β form. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1629–1637, 2001