Effect of drawing stress on mesophase structure formation of poly(ethylene 2,6-naphthalene dicarboxylate) fiber just after the neck-drawing point

Abstract

The structural development of poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) fibers was analyzed by in situ X-ray diffraction and fiber temperature measurements. The PEN fiber was drawn continuously under three drawing stresses, where the neck-drawing point was fixed accurately by CO2 laser irradiation heating. The developed crystal structures of the drawn fibers depended on the drawing stresses, that is, only the α-crystal was obtained under a drawing stress of 148 MPa, an α-rich mixed crystal was obtained for 54 MPa, and a β-rich mixed crystal was obtained under 23 MPa stress. Fiber containing over 70% β-crystal was obtained in the third case. Orientation-induced crystallization rates (K) and crystallization induction times (t0) were estimated for the three drawing stresses: K= 2210 s -1 and t0= 0.5 ms for 148 MPa, K= 940 s -1 and t0= 1.0 ms for 54 MPa, and K= 655 s -1 and t0= 4.0 ms for 23MPa. In addition, the drawing stress acted as a definitive influence not only on the resulting crystal form but also on the chain conformation of the mesophase structure. The d-spacing of the (001') diffraction increased with drawing stress, and the longer (001') spacing generated the α-crystal while the comparatively shorter (001') spacing yielded the β-crystal. The dspacings of 1.27 and 1.23 nm for the drawing stresses of 148 and 23 MPa, respectively, were somewhat shorter than the c-axis lengths of the α-and β-crystals of 1.32 and 1.27 nm, respectively.

Effect of melt spinning conditions on the fiber structure development of polyethylene terephthalate

“…The smectic phase is a metastable structure first reported by Bonart [21], and has also been observed for PEN [14] and PBT [22]. The smectic phase has been formed during batch drawing [23] and heat treatment of oriented amorphous PET [24].…”

“…There have been similar trials for producing high-strength fibers, collectively referred to as "melt structure control", which formed uniform molecular network structures by controlling the melt spinning process [2][3][4][5][6][7][8][9]. Fiber structure development after neck drawing has been observed for PET [10][11][12][13]18], polyethylene naphthalate (PEN) [14], polypropylene [15], polyphenylene sulfide [16], and polybutylene terephthalate (PBT) [17] in wide-angle X-ray diffraction (WAXD) and small-angle Xray scattering (SAXS) images captured with synchrotron X-rays at SPring-8. In particular, we previously analyzed the effect of the draw ratio on the fiber structure development of PET [10].…”

Ultra-SAXS observation of fibril-sized structure formation after the necking of poly(ethylene terephthalate) and poly(phenylene sulfide) fibers

“…This smectic phase is a metastable structure, first reported by Bonart [22], and has been formed during batch drawing [11] and heat treatment of oriented amorphous PET [23]. The smectic phase has also been observed for PEN [24] and PBT [25], although it has not been observed for PPS [20]. The period of 200 nm, corresponding to the layer-lined USAXS streak, can be assumed as the period of layered bundle of a fibrillar-shaped smectic phase of approximately 70 nm in length [12] and inter-fibrillar molecules.…”

Controlling Crystal Microstructure To Minimize Loss in Polymer Dielectrics

“…Crystalline PEN primarily adopts a triclinic unit cell with one chain per cell (α-form), , although a second isomorph can be obtained under certain high temperature conditions (β-form), which is also triclinic but has a larger cell to accommodate four chains. , Previous studies have explored the effect of thermal treatment − and orientation ,,,,,,,− on the semicrystalline morphology of PEN films. The presence of RAF ,− ,, or development of an oriented mesophase on drawing ,, has been inferred in a few cases for PEN as well.…”

“…64,65 Previous studies have explored the effect of thermal treatment 66−76 and orientation 45,46,55,66,71,72,75,77−80 on the semicrystalline morphology of PEN films. The presence of RAF 49,[62][63][64]67,72 or development of an oriented mesophase on drawing 45,46,81 has been inferred in a few cases for PEN as well.…”