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

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 alpha-crystal was obtained under a drawing stress of 148 MPa, an alpha-rich mixed crystal was obtained for 54 MPa, and a beta-rich mixed crystal was obtained under 23 MPa stress. Fiber containing over 70% beta-crystal was obtained in the third case. Orientation-induced crystallization rates (K) and crystallization induction times (t(0)) were estimated for the three drawing stresses: K = 2210 s(-1) and t(0) = 0.5 ms for 148 MPa, K = 940 s(-1) and t(0) = 1.0 ms for 54 MPa, and K= 655 s(-1) and t(0) = 4.0 ms for 23 MPa. 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 alpha-crystal while the comparatively shorter (001') spacing yielded the beta-crystal. The d-spacings 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 alpha- and beta-crystals of 1.32 and 1.27 nm, respectively.ArticlePOLYMER. 53(19):4272-4279 (2012)journal articl

In situ study of fiber structure development of poly(butylene terephthalate) in a continuous laser-heated drawing process

The structural development of poly(butylene terephthalate) (PBT) fibers was analyzed using in situ wide angle X-ray diffraction and fiber temperature measurements during CO2 laser-heated drawing, in which the necking position on the running fiber could be fixed by CO2 laser irradiation. The measured parameters were determined as functions of the elapsed time after necking with a time resolution of 0.3 ms. The as-spun PBT fibers, which exhibited a low-oriented alpha-crystalline structure, were drawn to a draw ratio of 5 using laser heating. The (001') reflection, which indicates a quasi-smectic fibrillar structure, was not observed before crystallization in contrast to measurements of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalene dicarboxylate) (PEN). The alpha-crystal was transformed into an oriented beta-form crystal at the necking position, and the developed beta-crystallites exhibited increased size and altered orientation <2 ms after necking. The fiber temperature increased rapidly at around T-g, and the rearrangement of the beta-crystal primarily occurred as the fiber's temperature rose from 100 to 160 degrees C. The oriented beta-crystal of the drawn fiber transformed into the oriented beta-crystal when the drawing tension was released. Polymer Journal (2012) 44, 1030-1035; doi: 10.1038/pj.2012.65; published online 18 April 2012ArticlePOLYMER JOURNAL. 44(10):1030-1035 (2012)journal articl

Strain-Induced Deformation of Glassy Spherical Microdomains in Elastomeric Triblock Copolymer Films: Time-Resolved 2d-SAXS Measurements under Stretched State

We have found extremely low efficiency of the elastomeric properties for SEBS (polystyrene-<i>block</i>-poly­(ethylene-<i>co</i>-butylene)-<i>block</i>-polystyrene) triblock copolymers having short polystyrene (PS) block chains. Since the SEBS specimens form spherical PS microdomains embedded in the matrix of the rubbery poly­(ethylene-<i>co</i>-butylene) (PEB) chains, they exhibit elastomeric properties (thermoplastic elastomer film). However, it was found that the stress was dramatically decreased with time when the specimens were stretched and fixed at strain of 4.0. Furthermore, they showed macroscopic fracture with very short-term duration (400 s to 2 h). To reveal the reason for such low efficiency, we conducted time-resolved two-dimensional small-angle X-ray scattering (2d-SAXS) measurements for the SEBS triblock copolymer films under stretched state at strain of 4.0. Upon stretching, the strain-induced deformation (not fracture) of glassy microdomains was observed. In addition, the deformation of glassy microdomains was found to proceed as time elapsed. Since this deformation of the glassy PS microdomains is considered to result in such the low efficiency of the elastomeric properties, characteristic times related to the deformation and the stress relaxation were evaluated from the change in strain of the glassy microdomains and from the stress relaxation curves, respectively. Then, good agreements of the characteristic times were found, and therefore it was concluded that the deformation of the glassy microdomains has a strong correlation with the stress relaxation and therefore with the fracture of the elastomeric film specimen

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

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 alpha-crystal was obtained under a drawing stress of 148 MPa, an alpha-rich mixed crystal was obtained for 54 MPa, and a beta-rich mixed crystal was obtained under 23 MPa stress. Fiber containing over 70% beta-crystal was obtained in the third case. Orientation-induced crystallization rates (K) and crystallization induction times (t(0)) were estimated for the three drawing stresses: K = 2210 s(-1) and t(0) = 0.5 ms for 148 MPa, K = 940 s(-1) and t(0) = 1.0 ms for 54 MPa, and K= 655 s(-1) and t(0) = 4.0 ms for 23 MPa. 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 alpha-crystal while the comparatively shorter (001') spacing yielded the beta-crystal. The d-spacings 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 alpha- and beta-crystals of 1.32 and 1.27 nm, respectively.ArticlePOLYMER. 53(19):4272-4279 (2012)journal articl