Draw characteristics of all aromatic copolyester melts in Electrospinning
Takashi Eguchi, Yoshiaki Taguchi*, Hiroshi Ito, Yuji Jinbo,
Sathish K. Sukumaran, Masataka Sugimoto, Kiyohito Koyama
Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan*Research and Development Center, Polyplastics Co., Ltd., Miyajima, Fuji, Shizuoka, Japaneguchi@ckpss.yz.yamagata-u.ac.jp
1. Introduction
Electrospinning uses an applied potential difference to draw fine fibers from a liquid. Usually, theliquid from which the fiber is drawn is stored in a syringe fitted with a needle. When the fiber draw
direction is horizontal a potential difference is necessary to draw the liquid from the needle tip anddeposit the resulting fiber onto the collector plate. In some cases, this can be accomplished bygravity alone by changing the geometry of the set-up. Even in this case, a sufficiently high potential
difference is necessary to establish a continuous liquid jet. Increasing the potential difference justincreases the volume rate of flow out of the needle tip. However, for certain all aromaticcopolyester melts novel behavior is observed. For one of the melts, at a certain voltage difference, acontinuous jet is established as expected. Surprisingly, upon increasing the potential difference
beyond a certain value, the melt is not drawn but remains around the tip of the syringe for several
seconds after the voltage is switched on. More interestingly, the melt is then drawn out of the tip fora centimeter or two but then the liquid jet suddenly stops in mid-flight and recoils back into thesyringe. To the best of our knowledge, such behavior has hitherto not been reported.
2. Experiment
We used two different all aromatic copolyesters D950 andabA950. A950 is similar to commercially available all aromaticcopolyesters but at roughly half the molecular weight. D950
is a specially formulated resin. During electrospinning, thetip to collector distance is fixed at 5cm. D950 was spun at360oC and A950 at 320oC. Under these spinning conditions,both the polymers have almost identical viscosities. Thedc
structure of the produced fiber was characterized using
Small Angle X-ray Scattering (SAXS).
3. Results and Discussion
Fig.1 SAXS profiles from fibers
Electrospinning:fabricated at 0kV/cmA950– D950 (a),A950 (b); at 2kV/cm - D950 (c),At electric field strength of 4kV/cm, a continuous liquid
A950 (d). Arrow: fiber direction.
jet was observed from both D950 and A950. When theD95
A950
applied voltage is higher than 6kV/cm, a continuous jet isstill observed from A950. However, for D950 afterswitching on this potential difference, the melt remains
around the tip of the syringe for several seconds. It is thendrawn out of the tip in a continuous filament for about two
centimeters but then swiftly recoils back into the syringe.
Domain Structure: SAXS profile:Figure 1 shows the SAXS profiles obtained from D950
and A950 fibers for two different applied voltages. At
0kV/cm, both A950 and D950 fibers have strong streaks
along the horizontal direction, see Figure 1(a), (b). The
strong horizontal streaks suggest that nanoscale structures Fig2. Azimuthal intensities extractedoriented along the fiber axis exist. If we remove this strong from the data shown in Fig. 1.
streak, then the remaining intensity is essentially isotropic in the case of A950, but there is strong
anisotropy due to the scattered intensity being almost diamond shaped for D950. At 2kV/cm, thescattering profile for A950 shows very little change from the 0kV/cm case but the D950 profile
appears less anisotropic and the scattered intensity is significantly weaker at the higher-q values, see
Figure 1(c), (d). Further work will involve understanding the origin of these scattering patterns interms of the fiber structure and determining the quantitative characteristics of the fibers from theirscattering curves.