• Korea-Australia Rheology Journal
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• v.12 no.2
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• pp.119-124
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• 2000

Employing the Phan-Thien tanner (PTT) fluids model, dynamic behavior of the non-isothermal melt spinning has been investigated. Subjects such as draw resonance instability, the effects of spinline cooling and of the fluid viscoelasticity on the spinning dynamics have been studied using the governing equations of the system. In particular, the draw resonance criterion based on the traveling times of various kinematic waves in the spinline has been confirmed, the reason why the spinline cooling is stabilizing is analyzed, and the effect of fluid viscoelasticity on the spinline stability is summarized. It is believed that the same method as in this study can be applied with equal ease to other extension deformation processes like film casting and film blowing.

• Carbon letters
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• v.15 no.2
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• pp.129-135
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• 2014

Spinnable pitch for melt-electrospinning was obtained from pyrolized fuel oil by electron beam (E-beam) radiation treatment. The modified pitch was characterized by measuring its elemental composition, softening point, viscosity, molecular weight, and spinnability. The softening point and viscosity properties of the modified pitch were influenced by reforming types (heat or E-beam radiation treatment) and the use of a catalyst. The softening point and molecular weight were increased in proportion to absorbed doses of E-beam radiation and added $AlCl_3$ due to the formation of pitch by free radical polymerization. The range of the molecular weight distribution of the modified pitch becomes narrow with better spinning owing to the generated aromatic compounds with similar molecular weight. The diameter of melt-electrospun pitch fibers under applied power of 20 kV decreased 53% ($4.7{\pm}0.9{\mu}m$) compared to that of melt-spun pitch fibers ($10.2{\pm}2.8{\mu}m$). It is found that E-beam treatment for reforming could be a promising method in terms of time-savings and cost-effectiveness, and the melt-electrospinning method is suitable for the preparation of thinner fibers than those obtained with the conventional melt-spinning method.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1023-1024
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• 2006

Al-8Fe-2Mo-2V-1Zr alloys were prepared by the gas atomization/hot extrusion and the melt spinning/hot extrusion. For the gas atomized and extruded alloy, equiaxed grains with the average size of 400 nm and finely distributed dispersoids with their particle sizes ranging from 50nm to 200nm were observed. For the melt spun and hot extrusion processed alloy, refined microstructural feature consisting of equiaxed grains with the average size of 200nm and fine dispersoids with their particle sizes under 50nm appeared to exhibit a difference in microstructure. Strength of the latter alloy was higher than that for the former alloy up to elevated temperatures.

• Analytical Science and Technology
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• v.8 no.3
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• pp.341-350
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• 1995

$Nd_{14}Fe_{80}B_6$ ribbon alloy was manufactured with using melt-spinning method and analyzed the magnetic properties according to the manufacturing conditions. The microstructure and magnetic properties of melt-spun ribbons are sensitively dependent on the quench rate and annealing conditions. As-quenched $Nd_{14}Fe_{80}B_6$ ribbons with optimum magnetic properties are obtained at wheel speed($v_s$) of about 20m/sec and over quenched ribbons show optimum magnetic properties at $v_s$=22m/see when annealed for 30 minutes at $600^{\circ}C$ under vacuum. The crystallization temperature($T_k$) of $Nd_2Fe_{14}B$ phase is about $595^{\circ}C$ in the DTA analysis.

• Carbon letters
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• v.19
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• pp.89-98
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• 2016

Taguchi’s experimental design was employed in the melt spinning of molten mesophase pitch to produce carbon fibers. The textures of the obtained carbon fibers were radial with varied crack angles, as observed by scanning electron microscopy and polarized optical imaging. The diameter, crack angle, preferred orientation, and tensile modulus of the produced samples were examined to investigate the influence of four spinning variables. The relative importance of the variables has been emphasized for each characteristic. The results show that thicker carbon fiber can be obtained with a smaller entry angle, a higher spinning temperature, a reduced winding speed, and an increased extrusion pressure. The winding speed was found to be the most significant factor in relation to the fiber diameter. While it was observed that thicker carbon fiber generally shows improved preferred orientation, the most important variable affecting the preferred orientation was found to be the entry angle. As the entry angle decreased from 120° to 60°, the shear flow was enhanced to induce more ordered radial alignment of crystallite planes so as to obtain carbon fibers with a higher degree of preferred orientation. As a consequence, the crack angle was increased, and the tensile modulus was improved.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.75-76
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• 1996

다공성 고분자 분리막을 제조하는 방법으로 기존의 용매교환법을 대신하여 내용매성, 내약품성 및 내열성이 매우 뛰어난 고분자를 소재로하여 다공성 고분자막을 만드는 열유도 상분리법(Thermally Induced Phase Separation, TIPS)이 개발되었다. TIPS공정에서는 주로 고분자/희석제 system의 열역학적인 불안정성에 의하여 polymer-rich phase와 polymer-lean phase로 상이 분리되는 liquid-liquid phase separation과 결정성 고분자의 결정화에 의한 solid-liquid phase separation을 주로 상분리 mechanism으로 사용하고 있다. 따라서 위에 언급된 TIPS 이론에 근거한 melt spinning 공정에 의하여 PP 중공사막을 제조하였는데 wet spinning 공정에 의한 용매 교환법에 비해 비교적 공정이 단순하고 다공도를 조건하기가 용이하며 구조 및 성능면에서도 높은 재현성을 가지고 있다. 또한 우수한 소재임에도 불구하고 절절한 용매의 부재로 용매교환법에서 사용할 수 없었던 폴리올레핀계, 나일론계, 방향족출합계 고분자를 사용할 수 있게 되어 소재의 폭이 넓어졌다는데에 가장 큰 장점이 있다. 본 연구에서는 PP중공사막을 제조하기 위하여 먼저 용융 방사장치를 제작하였고 melt spinning 공정에 의해 막을 제조하는데 적합한 방사조건들을 확립한 후 결정된 방사조건에 의해 얻어진 PP 중공사막의 구조 및 성능에 영향을 미치는 인자들에 관하여 조사하였다.

• Korea-Australia Rheology Journal
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• v.21 no.3
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• pp.149-153
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• 2009

Profile development of the melt spinning process of poly(ethylene terephthalate) (PET) was simulated by a numerical method under the consideration of two constitutive equations of Newtonian and upper convected Maxwell (UCM) models. The viscoelastic characteristics of the polymer were considered via UCM constitutive equation that considered relaxation time as a function of temperature and molecular weight. The UCM model predicted the diameter profile better than the Newtonian, while velocity development was slower than the Newtonian model. Viscoelasticity played an important role in accurately predicting diameter profile. However, even though neck-like deformation was observed in the UCM model, the exact position of the deformation under high speed spinning was not obtained.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.707-710
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• 1999

Moisture content and intrinsic viscosity of antistatic polyethyleneterephthalate(PET) depending on the thermal stabilizer content was studied. The terminal moisture content of antistatic PET was a function of drying temperature rather than drying time. Intrinsic viscosity drop of antistatic PET after melt spinning increased with increasing moisture content of it. After melt spinning, intrinsic viscosity of antistatic PET was decreased due to the thermal degradation of polyoxyalkyleneglycol(POAG) component of antistatic agent. Triphenylphosphate(TPP) was more effective as a thermal stabilizer than trimethylphosphate(TMP). A little intrinsic viscosity drop after melt spinning was found in PET containing 300 ppm of TPP as a thermal stabilizer.

• Carbon letters
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• v.3 no.1
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• pp.33-38
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• 2002

Petroleum based isotropic pitch was spun into short fiber by melt-blown spinning technology. The processing parameters chosen were air velocity, die temperature, and throughput rate of the pitch within the ranges of experimental tolerances. The fiber diameter was reduced to $6{\mu}m$ by increases of hot air velocity, and spin die temperature. Also, the fiber diameter was strongly dependent on the throughput rate of the pitch and jet speed of hot air through the spinnerets. Even fibers with $10{\mu}m$ diameter were produced at throughput rate of $0.17g/min{\cdot}hole$ and at die temperature of $290^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.6
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• pp.362-368
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• 2005

Formation and thermal stability of a quasicrystalline phases in Al-Fe-Mo alloys were investigated by means of melt-spinning process and subsequent heat treatment test. Thermal decomposition and phase transformation process of the as-spun alloys were studied using X-ray diffraction and electron microscopy. The melt-spun Al-Fe-Mo alloys contained an icosahedral quasicrystalline phase with a quasilattice constant of 0.457 nm. Icosahedral phase formed at a composition of $Al_{82.5}Fe_{14}Mo_{3.5}$ as a metastable phase during rapid solidification was transformed into the stable crystalline phases, cubic 1/0 approximant and monoclinic ${\lambda}$-phase, upon heating. A metastable icosahedral and cubic(a = 0.93 nm) phases in as-spun $Al_{65}Fe_{20}Mo_{15}$ alloy were decomposed into two cubic(a = 0.62, 0.31 nm) phases by heat treatment.