Structural Change of High-Speed Spun Poly (ethylene 2,6-naphthalene dicarboxylate) Fibers with Annealing.

Abstract

The as-spun poly(ethylene 2,6-naphthalene dicarboxylate)

Advances in the Production of Poly(ethylene naphthalate) Fibers

“…This also predicts that the necking position shift toward the spinneret with increasing take-up speed, as observed by Iizuka and Yabuki 88 and Miyata et al 32 In addition to the b modification, the a modification could also form in the PEN fibers by the aid of the spinline stress. 32,68,73,82,90 It was reported that the content of the a crystals increased with increasing take-up speed. 68 At the same time, the amount of the a crystals relative to that of the b crystals decreased 32 because the content of the b crystals increased more rapidly at higher speeds.…”

“…The semicrystalline PEN fibers often contain oriented amorphous portion which can further crystallize during heat-treatment. Miyata et al 82 found that when constrained annealing the PEN as-spun fibers, which had been either crystallized into the b modification at higher take-up speeds, or remained amorphous at lower take-up speeds, at temperatures from 200 to 2808C, the a modification always formed. Once the annealing temperature was raised to 2808C, the b modification started to appear in the fibers even if the fibers had been taken up at low speeds.…”

“…Therefore, the overall effect of the heat-treatment is to improve the crystallinity of the PEN fibers. 37,74,75,82 The heat-treatment can also induce a crystal transition in the PEN fibers. It was reported that the b to a crystal transition could occur at a temperature just above the cold crystallization temperature, i.e., 2008C 73 or 2408C.…”

“…This was usually attributed to the formation of the b crystals at higher speeds because the b crystals were believed to have a higher T m than the a crystals. 37,82,89 On the other hand, Buchner et al 26 suggested that the T m of both the a and b crystals strongly depended on the annealing conditions and the resultant crystalline morphology. Therefore, the increased T m could also result from the strain-and/or stress-induced increase in crystal size and/or crystal perfection.…”

Morphological study by TEM on uniaxially oriented thin films of PET, PEN and their blends

“…In this study, however, the result reported by Buchner et al, which was cited in the report by Miyata et al [29] on high-speed spun PEN fibers produced from 'same' pellets, was used for indexing the reflections assigned to b-modification in our SAED patterns, because in our next paper the uniaxially oriented thin film of PEN will be morphologically compared with the high-speed spun PEN fibers.…”