Mechanical properties and superstructure of poly(ethylene terephthalate) fibers zone-drawn and zone-annealed by CO2 laser heating

A laser-heating zone-drawing and zone-annealing method using a continuous-wave carbon dioxide laser was applied to poly(ethylene terephthalate) (PET) fiber to improve its mechanical properties. The as-spun fiber was zone-drawn under a applied tension (σ_a) of 4.44 MPa at a laser power density (PD) of 6.08 W cm⁻², and then the laser-heated zone-drawn fiber was zone-annealed. The laser-heating zone-annealing was carried out in three steps: the first annealing was carried out under σ_a = 139 MPa at 4.83 W cm⁻²; the second annealing was carried out under σ_a = 283 MPa at 4.83 W cm⁻², and the third annealing was carried out under σ_a = 432 MPa at 3.45 W cm⁻². The surface temperature distribution of the fiber irradiated with the CO₂ laser was measured by using an infrared thermographic camera equipped with a magnifying lens. The relation between the laser power and the surface temperature of the fiber became clear in the laser-heating zone-drawing and the laser-heating zone-annealing. The fiber obtained finally had a birefringence of 0.239, a degree of crystallinity of 55%, a tensile modulus of 19.8 GPa, and a storage modulus of 25.7 GPa at 25°C. In FTIR measurements, a trans conformation increased with the processing, but a gauche one decreased. The laser-heating zone-drawing and zone-annealing method was found to be effective in producing the PET fiber with high modulus and high strength. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2775–2783, 2001     

Nylon 66 nanofibers prepared by CO2 laser supersonic drawing

Nylon 66 nanofibers were prepared by irradiating as‐spun nylon 66 fibers with radiation from a carbon dioxide (CO₂) laser while drawing them at supersonic velocities. A supersonic jet was generated by blowing air into a vacuum chamber through the fiber injection orifice. The fiber diameter depended on the drawing conditions used, such as laser power, chamber pressure, laser irradiation point, and fiber supply speed. A nanofiber obtained at a laser power of 20 W and a chamber pressure of 20 kPa had an average diameter of 0.337 μm and a draw ratio of 291,664, and the drawing speed in the CO₂ laser supersonic drawing was 486 m s^?1. The nanofibers showed two melting peaks at about 257 and 272°C. The lower melting peak is observed at the same temperature as that of the as‐spun fiber, whereas the higher melting peak is about 15°C higher than the lower one. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40015.     

High temperature zone‐drawing of nylon 66 microfiber prepared by CO2 laser‐thinning

A high temperature zone‐drawing method was applied to a nylon 66 microfiber, obtained by using CO₂ laser‐thinning, to develop its mechanical properties. The microfiber used for the high temperature zone‐drawing was prepared by winding at 150 m min^?1 the microfiber obtained by irradiating the laser at 4.0 W cm^?2 to an original fiber with a diameter of 50 μm, and had a diameter of 9.6 μm and a birefringence of 0.019. The high temperature zone‐drawing was carried out in two steps; the first drawing was carried out at a temperature of 230°C at supplying and winding speeds of 0.266 and 0.797 m min^?1, the second at 250°C at supplying and winding speeds of 0.266 and 0.425 m min^?1, respectively. The diameter of the microfiber decreased, and its birefringence increased stepwise with the processing. The high temperature zone‐drawn microfiber finally obtained had a diameter of 4.2 μm, a birefringence of 0.079, total draw ratio of 4.8, tensile modulus of 12 GPa, and tensile strength of 1.0 GPa. The wide‐angle X‐ray diffraction photograph of the drawn microfiber showed the existence of highly oriented crystallites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 42–47, 2006     

Mechanical properties and microstructure of poly(ethylene terephthalate) microfiber prepared by carbon dioxide laser heating

We determined that a poly(ethylene terephthalate) microfiber was easily obtained by irradiating a carbon dioxide laser to an annealed fiber. The annealed fiber was prepared by zone drawing and zone annealing. First, an original fiber was zone drawn at a drawing temperature of 90°C under an applied tension of 4.9 MPa, and the zone‐drawn fiber was subsequently zone annealed at 150°C under 50.9 MPa. The zone‐annealed fiber had a degree of crystallinity of 48%, a birefringence of 218.9 × 10^?3, tensile modulus of 18.8 GPa, and tensile strength of 0.88 GPa. The microfiber prepared by laser heating the zone‐annealed fiber had a diameter of 1.5 μm, birefringence of 172.8 × 10^?3, tensile modulus of 17.6 GPa, and tensile strength of 1.01 GPa. The draw ratio estimated from the diameter was 9165 times; such a high draw ratio has thus far not been achievable by any conventional drawing method. Microfibers may be made more easily by laser heating than by conventional technologies such as conjugate spinning. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1955–1958, 2003     

Isotactic polypropylene microfiber prepared by continuous laser‐thinning method

An isotactic polypropylene (i‐PP) microfiber was continuously produced by using a carbon dioxide (CO₂) laser‐thinning apparatus developed in our laboratory. The CO₂ laser‐thinning apparatus could wind up the obtained microfiber in the range of 100 m min^?1 to 2500 m min^?1. The diameter of the microfiber decreased and its birefringence increased with increasing winding speed. When the microfiber obtained by irradiating the CO₂ laser operated at a power density of 31.8 W cm^?2 to the original fiber supplied at 0.30 m min^?1 was wound at 1,387 m min^?1, the obtained microfiber had a diameter of 3.5 μm and a birefringence of 25 × 10^?3. The draw ratio calculated from the supplying and the winding speeds was 4,623‐fold. The SEM photographs showed that the obtained microfibers had a smooth surface without a surface roughened by a laser‐ablation and were uniform in diameter. The wide‐angle X‐ray diffraction photographs of the microfibers wound at 848 and 1,387 m min^?1 showed the existence of the oriented crystallites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 27–31, 2006     

Superstructure and mechanical properties of nylon 66 microfiber prepared by carbon dioxide laser‐thinning method

Nylon 66 microfibers were obtained by a carbon dioxide (CO₂) laser‐thinning method. A laser‐thinning apparatus used to continuously prepare microfibers consisted of spools supplying and winding the fibers, a continuous‐wave CO₂‐laser emitter, a system supplying the fibers, and a traverse. The diameter of the microfibers decreased as the winding speed increased, and the birefringence increased as the winding speed increased. When microfibers, obtained through the laser irradiation (at a power density of 8.0 W cm^?2) of the original fiber supplied at 0.23 m min^?1, were wound at 2000 m min^?1, they had a diameter of 2.8 μm and a birefringence of 46 × 10^?3. The draw ratio calculated from the supplying and winding speeds was 8696×. Scanning electron microscopy showed that the microfibers obtained with the laser‐thinning apparatus had smooth surfaces not roughened by laser ablation that were uniform in diameter. To study the conformational transition with winding speed, the changes in trans band at 936 cm^?1 and gauche band at 1136 cm^?1 were measured with a Fourier transform infrared microscope. The trans band increased as the winding speed increased, and the gauche band decreased. Young's modulus and tensile strength increased with increasing winding speed. The microfiber, which was obtained at a winding speed of 2000 m min^?1, had a Young's modulus of 2.5 GPa and tensile strength of 0.6 GPa. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 802–807, 2006     

Poly(ethylene terephthalate) nanofibers prepared by CO2 laser supersonic drawing

Poly(ethylene terephthalate) (PET) nanofibers were prepared by irradiating a PET fiber with radiation from a carbon dioxide (CO₂) laser while drawing it at supersonic velocities. A supersonic jet was generated by blowing air into a vacuum chamber through the fiber injection orifice. The flow velocity from the orifice was estimated by computer simulation; the fastest flow velocity was calculated to be 401 m s⁻¹ at a chamber pressure of 6 kPa. A nanofiber obtained using a laser power of 8 W and a chamber pressure of 6 kPa had an average diameter of 193 nm and a draw ratio of about 900,000. This technique is a novel method for producing nanofibers.     

Zone drawing and zone annealing of poly(ethylene terephthalate) microfiber prepared by CO2 laser thinning

A zone‐drawing and zone‐annealing method was applied to a poly(ethylene terephthalate) microfiber, obtained by using CO₂ laser thinning, to develop its mechanical properties. The microfiber used for the zone drawing and zone annealing was prepared by winding at 1386 m/min the microfiber obtained by irradiating the laser at 18.1 W/cm² and had a diameter of 2.8 μm and a birefringence of 0.097. Zone drawing was carried out at a drawing temperature of 105°C under an applied tension of 53 MPa, and zone annealing at an annealing temperature of 155°C under 195 MPa applied tension. Zone drawing and zone annealing were carried out at a treatment speed of 0.21 m/min. The diameter of the microfiber decreased, and its birefringence increased, with zone drawing and zone annealing. The zone‐annealed microfiber finally obtained had a diameter of 2 μm, a birefringence of 0.234, a tensile modulus of 17.9 GPa, and a tensile strength of 1.1 GPa. The wide‐angle X‐ray diffraction photograph of the zone‐annealed microfiber showed the existence of highly oriented crystallites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2989–2994, 2004     

Application of CO2 laser heating zone drawing and zone annealing to nylon 6 fibers

Nlon 6 fibers were zone drawn and zone annealed by using a continuous wave carbon dioxide laser to develop their mechanical properties. A laser‐heating zone drawing was carried out under a applied tension of 35.4 MPa at a power density of 9.65 W · cm^?2, and then the zone‐drawn fiber was annealed. A laser‐heating zone annealing was carried out in two steps at a power density of 9.65 W · cm^?2; the first step was carried out under 423 MPa and the second under 517 MPa. The treating temperature of the fiber heated by the CO₂ laser was measured by using an infrared thermographic camera equipped with a magnifying lens. The treating temperature at the zone drawing is 138°C, and those at the first and the second zone annealing are 121 and 125°C, respectively. The second laser‐heated zone‐annealed fiber has a birefringence of 65.2 × 10^?3, a degree of crystallinity of 54%, and a storage modulus of 21 GPa at 25°C. Wide‐angle X‐ray diffraction patterns for the laser‐heated zone‐drawn and the zone‐annealed fibers show (200) reflection and (002/202) doublet due to only an α form on the equator. The laser‐heated zone‐drawn fiber has a melting endotherm peaking at 216°C and a trace of shoulder on the higher temperature side of its peak, and the laser‐heated zone‐annealed fibers have a single melting endotherm peaking at 216°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1711–1716, 2002     

Poly(ethylene‐2,6‐naphthalate) nanofiber prepared by carbon dioxide laser supersonic drawing

Poly(ethylene‐2,6‐naphthalate) (PEN) nanofiber was prepared by a carbon dioxide (CO₂) laser supersonic drawing. The CO₂ laser supersonic drawing was carried out by irradiating the laser to the as‐spun PEN fiber in a low‐temperature supersonic jet. The supersonic jet was generated by blowing off air into a vacuum chamber from a fiber supplying orifice. The flow velocity from the orifice can be estimated by applying Graham's theorem from the pressure difference between the atmospheric pressure and the pressure of the vacuum chamber. The fastest flow velocity estimated was 396 m s^?1 (Mach 1.15) at a chamber pressure of 6 KPa. The nanofiber obtained at Mach 1.15 was the oriented nanofibers with an average diameter of 0.259 μm, and its draw ratio estimated from the diameters before and after the drawing reached 430,822 times. The CO₂ laser supersonic drawing is a new method to make nanofiber without using any solvent or removing the second component. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Melt‐electrospinning of poly(ethylene terephthalate) and polyalirate

Rodlike polymer samples were made from three kinds of poly(ethylene terephthalate) (PET) pellets with different intrinsic viscosities (IV), and from polyalirate (Vectra) pellets. PET and Vectra fibers were produced using a melt‐electrospinning system equipped with a CO₂‐laser melting device from these rodlike samples. The effects of IV value and laser output power on the fiber diameter of PET were investigated. Furthermore, the effect of the laser output power on the fiber diameter of Vectra was investigated. The crystal orientation of these produced fibers was also investigated by X‐ray photographs. The following conclusions were reached: (i) the diameter of PET fiber decreases with increasing laser output power; (ii) the minimum average diameter of PET fibers is scarcely influenced by the value of IV; (iii) the electrospun PET fibers show isotropic crystal orientation; (iv) fibers having an average fiber diameter smaller than 1 μm cannot be obtained from PET and Vectra using the system developed; and (v) preferred liquid crystal orientation can be seen in electrospun Vectra fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Nylon 6 microfiber prepared by carbon dioxide laser heating

A nylon 6 microfiber was easily obtained through carbon dioxide laser heating. The laser heating was carried out in two steps: the first laser heating was performed under an applied tension of 36.7 MPa at a power density of 17.3 W cm^?2, and the second was performed under 0.18 MPa at 51.81 W cm^?2. The microfiber was obtained by the second laser heating of the fiber. The microfiber prepared under the optimum thinning conditions had a diameter of 1.9 μm and a birefringence of 46.2 × 10^?3. Its draw ratio, estimated from the diameter, was 9895× (so far, it has been impossible to achieve such a high draw ratio by drawing). A (200) reflection and a (002/202) doublet due to an α form were observed on the equator, but no (200) reflection due to a γ form was observed. The morphology of the crystallites existing in the microfiber was only the α form. Laser heating made the microfiber more easily than conventional technologies, such as conjugate spinning, melt blowing, and flash spinning. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1449–1453, 2004     

Novel CO2 laser drawing of thermotropic liquid crystal polymer and poly(ethylene 2,6‐naphthalate) blend fibers

Thermotropic liquid crystal polymer (TLCP)/poly(ethylene 2,6‐naphthalate) (PEN) were prepared by a melt blending, and were melt spun by a spin‐draw process. In this study, we suggest novel drawing technology using the CO₂ laser that can directly and uniformly heat up fiber inside to prevent the formation of ununiform structures in conventional heat drawing process. The properties of the heat/laser drawn TLCP/PEN blend fibers were superior to those of any other handled fibers, and were rather more excellent than those of TLCP/PEN blend fibers annealed at 135°C for 10 min. It was confirmed that the CO₂ laser drawing made it possible to achieve the optimal drawing effect by draw ratio. The combined heating and CO₂ laser‐drawing method has a great potential for industrial applications as a novel fiber‐drawing process, and it can also be applied continuously to conventional spin‐draw system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 205–211, 2007     

Isotactic polypropylene microfiber prepared by carbon dioxide laser‐heating

An isotactic polypropylene (i‐PP) microfiber was obtained by irradiating a carbon dioxide laser to previously drawn fibers. To prepare the thinner i‐PP microfiber, it is necessary to previously draw original i‐PP fibers under an applied tension of 7.8 MPa at a drawing temperature of 140°C. The drawn fiber was heated under an applied tension of 0.3 MPa using the laser operated at a power density of 39.6 W cm^?2. The thinnest i‐PP microfiber obtained under optimum conditions had a diameter of 1.8 μm and a birefringence of 30 × 10^?3. Its draw ratio estimated from the diameter reached 51,630. It is so far impossible to achieve such a high draw ratio by any drawing. The wide‐angle X‐ray diffraction photograph of the microfiber shows the existence of the oriented crystallites. Laser‐heating allows easier fabrication of microfibers compared with the conventional technology such as the conjugate spinning. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1534–1539, 2004     

Isotactic polypropylene hollow microfibers prepared by CO2 laser‐thinning

An isotactic polypropylene hollow microfiber was continuously produced by using a carbon dioxide (CO₂) laser‐thinning method. To prepare the hollow microfiber continuously, the apparatus used for the thinning of the solid fiber was improved so that the laser can circularly irradiate to the hollow fiber. Original hollow fiber with an outside diameter (OD) of 450 μm and an internal diameter (ID) of 250 μm was spun by using a melt spinning machine with a specially designed spinneret to produce the hollow fiber. An as‐spun hollow fiber was laser‐heated under various conditions, and the OD and the ID decreased with increasing the winding speed. For example, when the hollow microfiber obtained by irradiating the CO₂ laser to the original hollow fiber supplied at 0.30 m min^?1 was wound up at 800 m min^?1, the obtained hollow microfiber had an OD of 6.3 μm and an ID of 2.2 μm. The draw ratio calculated from the supplying and the winding speeds was 2667‐fold. The hollow microfibers obtained under various conditions had the hollowness in the range of 20–30%. The wide‐angle X‐ray diffraction patterns of the hollow microfibers showed the existence of the highly oriented crystallites. Further, the OD and ID decreased, and the hollowness increased by drawing hollow microfiber obtained with the laser‐thinning. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2600–2607, 2006     

Nonlinear optical response of liquid crystalline azo‐dendrimer in picosecond and CW regimes

The nonlinear optical response of the liquid crystalline multiarm star‐shaped azodendrimer was investigated in picosecond pulse and CW regimes at 532 nm. The polymer exhibited large nonlinear refractive coefficient in two regimes (n₂ = −2.88 × 10⁻¹³ cm²/W and −1.1 × 10⁻¹⁰ cm²/W under picoseconds pulse excitation, whereas n₂ = −1.4 × 10⁻⁶ cm²/W and n₂ = −8.8 × 10⁻⁵ cm²/W under CW laser excitation in solution and film, respectively). The mechanism accounting for the process of nonlinear refraction was discussed. The value of photoinduced birefringence in the polymer film was also measured (Δn ∼ 10⁻³) under CW laser excitation at 532 nm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Superstructure and mechanical properties of poly(L-lactic acid) microfibers prepared by CO2 laser-thinning

Poly(L-lactic acid) (PLLA) microfibers were obtained by a carbon dioxide (CO₂) laser-thinning method. A laser-thinning apparatus used to continuously prepare microfibers was developed in our laboratory; it consisted of spools supplying and winding the fibers, a continuous-wave CO₂-laser emitter, a system supplying the fibers, and a traverse. The laser-thinning apparatus produced PLLA microfibers in the range of 100-800 m min⁻¹. The diameter of the microfibers decreased as the winding speed increased, and the birefringence increased as the winding speed increased. When microfibers, obtained through the laser irradiation (at a laser power of 8.0 W cm⁻²) of the original fiber supplied at 0.4 m min⁻¹, were wound at 800 m min⁻¹, they had a diameter of 1.37 μm and a birefringence of 24.1×10⁻³. The draw ratio calculated from the supplying and winding speeds was 2000×. The degree of crystal orientation increased with increasing the winding speed. Scanning electron microscopy showed that the microfibers obtained with the laser-thinning apparatus had smooth surfaces not roughened by laser ablation that were uniform in diameter. The PLLA microfiber, which was obtained under an optimum condition, had a Young's modulus of 5.8 GPa and tensile strength of 0.75 GPa.     

Preparation of high-modulus poly(ethylene terephthalate) fibers by vibrating hot drawing

A novel drawing method, vibrating hot drawing, was successfully applied to poly(ethylene terephthalate) fiber, which has a normal molecular weight (IV = 0.7 dL/g) and was prepared by melt spinning. The process was divided into three steps, with differing conditions in drawing temperature, applied tension, vibrating frequency, and amplitude. The drawing temperature and vibration frequency were decided by considering the α_a dispersion of the polymer. In spite of a low draw ratio (7.7) and a low crystallinity (0.55), the birefringence and dynamic storage modulus at room temperature of the 3rd-step fiber reached 0.260 and 36 GPa, respectively. The modulus remains at a high level at elevated temperatures, for example, 29 GPa at 100°C and 17 GPa at 200°C. Further, it was found from temperature and intensity of the α_a dispersion peak that the movements of amorphous chains are strongly inhibited. © 1996 John Wiley & Sons, Inc.     

Poly(ethylene terephthalate) nanoparticles prepared by CO2 laser supersonic atomization

Poly(ethylene terephthalate) (PET) particles were prepared by the irradiation of PET fibers with a carbon dioxide (CO₂) laser while atomizing them at supersonic velocities. A supersonic jet was generated by blowing air into a vacuum chamber through a fiber injection orifice. The fibers are melted by laser heating and atomized by the supersonic jet at the outlet of the orifice. The PET particles produced by CO₂ laser supersonic atomization conducted at a laser power of 34 W and at a chamber pressure of 10 kPa have an average particle size of 0.619 μm, high circularity, and a smooth surface that is not roughened by laser ablation. The novel CO₂ laser supersonic atomization technique can be used to easily prepare polymeric nanoparticles of various thermoplastic polymers using only CO₂ laser irradiation without the need for solvents and additives. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40909.     

PBT/PET conjugated fibers: Melt spinning,fiber properties,and thermal bonding

This work examines the PBT/PET sheath/core conjugated fiber, with reference to melt spinning, fiber properties and thermal bonding. Regarding the rheological behaviors in the conjugated spinning, PET and PBT show the smallest difference between their melt‐viscosity at temperatures of 290°C and 260°C respectively, which has been thought to represent optimal spinning conditions. The effect of processing parameters on the crystallinity of core material‐PET was observed and listed. In order of importance, these factors are the draw ratio, the heat‐set temperature, and the drawing temperature. The crystallinity of sheath material‐PBT, however, can be considered to be constant, independent of any processing parameters. The bulk orientation, rather than the crystallinity of PET core, dominates the tenacity of PBT/PET sheath/core fiber. Moreover, heat‐set treatment after drawing is recommended to yield a highly oriented conjugated fiber. With respect to thermal bonding, PBT/PET conjugated fibers processed via high draw ratio but low‐temperature heat setting can form optimal thermal bonds at a constant bonding temperature of 10°C above the T_m of PBT.