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1.
To increase the spinning speed of poly(trimethylene terephthalate) (PTT) fibers, polystyrene (PS) was selected as an additive
polymer in the PTT matrix. Mixing of the immiscible PS with PTT led to an increase in spinning speed up to 5,500 m/min. PS
was employed to improve the extensibility of the matrix PTT in the spinning process as it can prevent PTT molecular orientation.
Experimental results show that the mixing of PS achieved this. The elongation at break of spun fibers increased with the amount
of PS. PS addition prevented fiber orientation, especially amorphous orientation, and improved drawability, and as such, increased
spinning speed up to 5,500 m/min. 相似文献
2.
High-speed melt spinning of syndiotactic polystyrene was carried out using high and low molecular weight polymers, HMs-PS and LMs-PS, at the throughput rates of 3 and 6 g/min. The effect of take-up velocity on the structure and properties of as-spun fibers
was investigated. Wide angle X-ray diffraction (WAXD) patterns of the as-spun fibers revealed that the orientation-induced
crystallization started to occur at the take-up velocities of 2–3 km/min. The crystal modification wasα-form. Birefringence of as-spun fibers showed negative value, and the absolute value of birefringence increased with an increase
in the take-up velocity. The cold crystallization temperature analyzed through the differential scanning calorimetry (DSC)
decreased with an increase in the take-up velocity in the low speed region, whereas as the melting temperature increased after
the on-set of orientation-induced crystallization. It was found that the fiber structure development proceeded from lower
take-up velocities when the spinning conditions of higher molecular weight and lower throughput rate were adopted. The highest
tensile modulus of 6.5 GPa was obtained for the fibers prepared at the spinning conditions of LMs-PS, 6 g/min and 5 km/min, whereas the highest tensile strength of 160 MPa was obtained for the HMs-PS fibers at the take-up velocity of 2 km/min. Elongation at break of as-spun fibers showed an abrupt increase, which was
regarded as the brittle-ductile transition, in the low speed region, and subsequently decreased with an increase in the take-up
velocity. There was a universal relation between the thermal and mechanical properties of as-spun fibers and the birefringence
of as-spun fibers when the fibers were still amorphous. The orientation-induced crystallization was found to start when the
birefringence reached — 0.02. After the starting of the orientation-induced crystallization, thermal and mechanical properties
of as-spun fibers with similar level of birefringence varied significantly depending on the processing conditions. 相似文献
3.
Ismail Karacan 《Fibers and Polymers》2005,6(3):206-218
A selection of commercially available poly(ethylene terephthalate) fibers with different degrees of molecular alignment and
crystallinity have been investigated utilizing a wide range of techniques including optical microscopy, infrared spectroscopy
together with thermal and wide-angle X-ray diffraction techniques. Annealing experiments showed increased molecular alignment
and crystallinity as shown by the increased values of birefringence and melting enthalpies. Crystallinity values determined
from thermal analysis, density, unpolarized infrared spectroscopy and X-ray diffraction are compared and discussed in terms
of the inherent capabilities and limitations of each measurement technique. The birefringence and refractive index values
obtained from optical microscopy are found to decrease with increasing wavelength of light used in the experiments. The wide-angle
X-ray diffraction analysis shows that the samples with relatively low orientation possess oriented non-crystalline array of
chains whereas those with high molecular orientation possess well defined and oriented crystalline array of chains along the
fiber axis direction. X-ray analysis showed increasing crystallite size trend with increasing molecular orientation. SEM images
showed micro-cracks on low oriented fiber surfaces becoming smooth on highly oriented fiber surfaces. Excellent bending characteristics
were observed with knotted fibers implying relatively easy fabric formation. 相似文献
4.
Ismail Karacan 《Fibers and Polymers》2005,6(3):186-199
A selection of commercially available poly(ethylene terephthalate) fibers with different degrees of molecular alignment and
crystallinity have been investigated utilizing a wide range of techniques including optical microscopy, infrared spectroscopy
together with thermal and wide-angle X-ray diffraction techniques. Annealing experiments showed increased molecular alignment
and crystallinity as shown by the increased values of birefringence and melting enthalpies. Crystallinity values determined
from thermal analysis, density, unpolarized infrared spectroscopy and X-ray diffraction are compared and discussed in terms
of the inherent capabilities and limitations of each measurement technique. The birefringence and refractive index values
obtained from optical microscopy are found to decrease with increasing wavelength of light used in the experiments. The wide-angle
X-ray diffraction analysis shows that the samples with relatively low orientation possess oriented non-crystalline array of
chains whereas those with high molecular orientation possess well defined and oriented crystalline array of chains along the
fiber axis direction. X-ray analysis showed increasing crystallite size trend with increasing molecular orientation. SEM images
showed micro-cracks on low oriented fiber surfaces becoming smooth on highly oriented fiber surfaces. Excellent bending characteristics
were observed with knotted fibers implying relatively easy fabric formation. 相似文献
5.
In this work, the method, in principle of the box complex algorithm was adopted to obtain stress-induced crystallization coefficient
C and the strain-optical coefficientA
op
with the value of 295 and 1.5×10−9, respectively, and some parametersA
1=0.27,A
2=5.06,a=3.5,b=1.8 relative to the elongational viscosity of poly(trimethylene terephthalate)(PTT) fiber. The vitrification distance as
a function of the take-up velocity and mass throughput was also gotten. The effects of spinning conditions on filament temperature,
velocity gradient, spinning tension, birefringence and crystallinity, and effect of viscoelasticity on take-up velocity had
been discussed. 相似文献
6.
Profiles development of the melt spinning process of poly(trimethylene terephthalate) (PTT) was simulated by a numerical method.
The spinning speed of 3 km/min to 5 km/min was analyzed and the characteristic of PTT spinning process was compared with that
of poly(ethylene terephthalate) (PET). Velocity development of PTT was slower than that of PET. Although PTT’s spinning temperature
was lower than PET’s, the PTT solidified slower because of a smaller super-cooling and the large specific heat capacity. The
diameter profile of PTT decreases gradually in comparison with that of PET. PTT’s strain rate has a broader distribution than
PET’s and its maximum ranged from 541 to 570 s−1 for PET and 136 to 149 s−1 for PTT. PTT’s tensile stress was smaller than PET’s. 相似文献
7.
A pitch precursor for a general purpose carbon fiber was prepared by condensation of pyrolized fuel oil (petroleum residual
oil) with bromine under nitrogen blowing. Such a condensation raised the softening point of the pitch from 40°C to 265°C with
a yield of 43%. The pitch precursor showed an enhanced aromaticity and enlarged molecular size, which led to a reduction in
molecular mobility and optical isotropy. The precursor was spun into fibers of 20 μm diameter at a take-up speed of 700 m/min.
The fiber was stepwise stabilized in air and carbonized in Ar gas to obtain an isotropic carbon fiber. The carbon fiber exhibited
tensile strengths of 500–800 MPa though the fiber was formed via a crude method. The electric conductivity of the carbon fiber
was relatively high, 2.2×102 S/cm, sufficient to be used as electrode materials. 相似文献
8.
The structure development and dynamic properties of fibers produced by high-speed spinning of P(EN-ET) random copolymers were
investigated. The as-spun fibers were found to remain amorphous up to the spinning speed of 1500 m/min, and subsequent increases
in speed resulted in the crystalline domains containing primarilyα crystalline modification of PEN. Theβ modification was not found up to spinning speeds of 4500 m/min. On the other hand, annealing of constrained fibers spun at
the 2100 m/min at 180, 200, and 240°C exhibitedβ-form crystalline structure, while the annealed fibers spun in 600–1500 m/min range exhibited dominantlyα-form. Howeverβ-form crystals disappeared above the spinning speed of 3000 m/min. With increasing spinning speeds from 600 to 4500 m/min,
the storage modulus of as-spun fibers increased continuously and reached a value of about 10.4 Gpa at room temperature. The
tanδ curves showed theα-relaxation peak at about 155–165°C, which is considered to correspond to the glass transition. Theα-relaxation peaks became smaller and broader, and shift to higher temperatures as the spinning speed increases, meaning that
molecular mobility in the amorphous region is restricted by increased crystalline domain. 相似文献
9.
The polyoxymethylene (POM) fiber was melt spun by use of different commercial grades of POM resin, and the effect of post-drawing on mechanical properties and microstructures was investigated extensively. The fiber obtained from the POM resin with a higher melt flow index (MFI) exhibits a better hot-drawing capability and also achieves a greater ultimate draw ratio. The mechanical evaluation reveals that the tensile strength and elastic modulus of POM fiber are improved significantly after post-drawing compared to the as-spun fibers. Although the greater draw ratios result in higher mechanical strength and modulus for the POM fiber, the fiber obtained from the POM resin with an MFI of 13.0 g/10 min achieves the optimal mechanical performance at the ultimate draw ratio. The morphologic and structural developments of POM fiber were studied by scanning electronic microscopy and X-ray powder diffraction. The results indicate that the POM fiber spun by the resin with an MFI of 13.0 g/10 min has a smooth lateral surface and a compact cross section after post-drawing. The fiber samples spun by the POM resins with low MFIs show some hollow disfigurements as well as a rough surface at the ultimate draw ratio, whereas the fiber obtained from the resin with a high MFI of 27.0 g/10 min presents the ununiformity of diameter after post-drawing. The POM fibers achieve a crystalline orientation during the hot-drawing process, which results in a transformation from the spherulitic crystals to the lamellar structure in the drawing direction. The level of crystalline orientation can be improved with an increase of draw ratio and thus results in a high modulus and strength for the resulting POM fiber samples. In addition, the thermal analysis indicates that the crystallinity of the as-spun fibers can be enhanced by post-drawing due to the orientation-induced crystallization. 相似文献
10.
In this study, the surface of polyester fiber was modified by means of thermal treatment with a silver carbamate complex. We used scanning electron microscopy (SEM), an X-ray diffraction technique (XRD), and X-ray photoelectron spectroscopy (XPS) to allow a detailed characterization of the silver-coated polyethylene terephthalate (PET) fibers. The results revealed remarkable changes in the surface morphology and microstructure of the silver film after thermal reduction. On SEM, the silver nanoparticles (AgNPs) were seen to be uniformly and densely deposited on the fiber surface. The XRD pattern of the silver-coated fiber indicated that the film has a crystalline structure. A continuous layer of AgNPs, between 30 and 100 nm in size, was assembled on the PET fibers. The PET/Ag composite was found to impart high conductivity to the fibers, with an electrical resistivity as low as 0.12 kΩ·cm. 相似文献
11.
Sang Youn Oh Dong Il Yoo Younsook Shin Hak Yong Kim Hwan Chul Kim Yong Sik Chung Won Ho Park Ji Ho Youk 《Fibers and Polymers》2005,6(2):95-102
Sodium cellulose carbonate (CC-Na) dissolved in 8.5 wt% NaOH/ZnO (100/2–3, w/w) aqueous solution was spun into some acidic
coagulant systems. Diameter of regenerated cellulose fibers obtained was in the range of 15–50μm. Serrated or circular cross sectional views were obtained by controlling salt concentration or acidity in the acid/salt/water
coagulant systems. Velocity ratio of take-up to spinning was controlled up to 4/1 with increasing spinning velocity from 5
to 40 m/min. Skin structure of was developed at lower acidity or higher concentration of coagulants. Fineness, tenacity and
elongation of the regenerated cellulose fibers were in the range of 1.5–27 denier, 1.2–2.2 g/d, and 8–11.3%, respectively.
All of CC-Na and cellulose fibers spun from CC-Na exhibited cellulose II crystalline structure. Crystallinity index was increased
with increasing take-up speed. 相似文献
12.
Melt-electrospinning is an efficient and environmental-friendly technique for producing nano/micro fibers. In this work, the self-layering behavior of poly(ethylene terephthalate)(PET) fiber deposition during melt-electrospinning was investigated based on the electric field simulation analysis by ANSYS and high voltage insulation theory of capacitor for melt-electrospinning configuration. The simulation results demonstrated that during melt-electrospinning process, the electric field strength on the center and lateral surface of the collector changed alternately when some electrically charged jet deposited, making jet depositing location moved around between center and lateral surface, resulted in the formation of the binding fibers separating the inner and outer layers in the deposited PET fiber web. The PET fiber web electrospun in 90 minutes could be laminated freely into thirteen layers. The geometric dimensions of these layers were measured and their morphologies were observed by scanning electron microscopy (SEM). These laminated layers were concentric with almost linearly increasing radius from the inner to the outer. Inner layers featured themselves with appearance of thick center and thin edge, while for outer layers, they presented the appearance of thin center and thick edge. The fibers in the web were quite uniformly and had diameters of about 2 μm. 相似文献
13.
Thermotropic liquid crystalline polymer made up of poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate) (PET) 8/2 copolyester, poly(ethylene 2,6-naphthalate) (PEN) and PET were
mechanically blended to pursue the liquid crystalline phase of ternary blends. Complex viscosities of blends decreased with
increasing temperature and PHB content. DSC thermal analysis indicated that glass transition temperature (Tg) and melting temperature (Tm) of blends increased with increasing PHB content. Both tensile strength and initial modulus increased with raising PHB content
and take-up speed of monofilaments. In the WAXS diagram, only PEN crystal reflection at 2Θ=15.5o appeared but PET crystal reflection was not shown in all compositions. The degree of transesterification and randomness of
blends increased with blending time but sequential length of both PEN and PET segment decreased. 相似文献
14.
Mechanical properties of biodegradable poly(butylene succinate-co-terephthalate) (PBST) fibers with 70 mol% butylene terephthalate (BT) were intensively investigated. Chemical structure composed of hard BT units and soft butylene succinate (BS) units made contributions to the higher elongation at break and lower initial modulus of PBST fibers than poly(butylene terephthalate) (PBT) fibers. Moreover, PBST fibers had better elastic properties than PBT fibers by exploring their elastic recovery. The stretch elastic recovery mechanism of PBST fibers was clarified from the point of crystal structure transition. According to the preliminary studies by wide angle X-ray diffraction (WAXD) measurements, two polymorphs (α form and β form) were confirmed when PBST fibers were applied to different deformations. With the help of intensive study by small angle X-ray scattering (SAXS) measurements, the crystal structure transition of PBST fibers was further verified. 相似文献
15.
Joo Hyung Hong Min Kyung Ku Yongjun Ahn Hyung Joo Kim Hyungsup Kim 《Fibers and Polymers》2013,14(12):2015-2019
In order to study the effects of the spinning conditions on the structure and the properties of the regenerated fiber, cellulose was dissolved in ionic liquid and then spun into fiber using an air-gap spinning process. The solution concentration, the take-up speed and the fixation of the fiber ends during coagulation improved the crystallinity and the tensile strength at the same time. The fiber surface became smooth by addition of DMF (dimethylformamide). However, it decreased the crystallinity and the tensile strength of the fibers. We revealed that the developed structure during coagulation determined the morphology and the properties of the fibers. The co-solvent resulted in smooth surface of the fiber and also changed the mechanical properties. 相似文献
16.
Solid-state polymerization of poly(trimethylene terephthalate)(PTT) was carried out to obtain high molecular weight polymers.
Two kinds of commercial PTT chips were polymerized in the solid state by the heat treatment at 190∼220°C for various times
and they were characterized by end group content, molecular weight, thermal analysis, and X-ray diffraction. In the solid-state
polymerization of PTT, the overall reaction rate was governed by the solid-state polymerization temperature and time, and
pellet size. The content of carboxyl end groups decreased during the solid-state polymerization with increasing solid-state
polymerization temperature and time. The melting temperature and crystallinity of the PTT were higher for the ones treated
at higher temperature and longer time. The activation energy for the solid-state polymerization of PTT was in the range of
24∼25 kcal/mol for both chips. Through the solid-state polymerization of commercial PTT chips, high molecular weight polymers
up to an intrinsic viscosity of 1.63 dl/g was obtained, which corresponded to about a 117,000 weight-average molecular weight. 相似文献
17.
Conductive polyaniline (PAn)/poly(ethylene terephthalate) (PET) composite fibers were prepared by chemical polymerization
of aniline in the presence of PET fibers using benzoyl peroxide (Bz2O2) in organic solvent/aqueous hydrochloric acid mixtures. The effects of polymerization conditions such as organic solvent/water
ratio, oxidant, aniline and hydrochloric acid concentrations and temperature were investigated on the amount of PAn deposited
on PET fiber and the electrical surface resistance of composite fibers. The maximum PAn content and the lowest electrical
surface resistance of composite fibers were observed at HCl concentrations of 0.5 mol L−1. The properties of PAn/PET composite fibers such as density, diameter, tensile strength and breaking elongation were also
investigated in comparison with those of pure PET. Characterization of conductive composite fibers was carried out by FTIR,
TGA, SEM techniques, surface resistance measurements, and cross section images taken by optical microscope. 相似文献
18.
In this study, we evaluated the effect of the molecular weight of the polymer on electrospun poly(ethylene terephthalate)
(PET) nonwovens, and their mechanical properties as a function of the linear velocity of drum surface. Polymer solutions and
electrospun PET nonwovens were characterized by means of viscometer, tensiometer, scanning electron microscope (SEM), wide
angle X-ray diffraction measurement (WAXD) and universal testing machine (UTM). By keeping the uniform solution viscosity,
regardless of molecular weight differences, electrospun PET nonwovens with similar average diameter could be obtained. In
addition, the mechanical properties of the electrospun PET nonwovens were strongly dependent on the linear velocity of drum
surface. From the results of the WAXD scan, it was found that the polymer took on a particular molecular orientation when
the linear velocity of drum surface was increased. The peaks became more definite and apparent, evolving from an amorphous
pattern at 0 m/min to peaks and signifying the presence of crystallinity at 45 m/min. 相似文献
19.
The cross-section shape, longitudinal self-crimping configuration of various PTT (Polytrimethylene terephthalate)/PET (Polyethylene terephthalate) filaments were observed and measured via microscope. The crimp parameters of the filaments, including helixes pitch, crimp radius, crimp curvature and regular crimp proportion were calculated, and the relationship between crimp parameters and self-crimping configurations of PTT/PET filament was analyzed. Various shapes of PTT/PET fiber cross-section were detected such as round, peanut, dog bone and pear like shapes. Crimp configurations were found not always regular spatial helix along the longitudinal direction of filament and had significant difference according to the fact whether the filament was undergone textured process. With the length rate of the long axis to the short axis of cross-section increasing, the crimp curvature of filament will also increase. The helix pitch and radius will increase while the crimp curvature will decrease with the increasing linear density for the same cross-section shape of PTT/PET filament. 相似文献
20.
PET yarns textured at different texturing conditions were treated with superheated steam or dry heat at different temperatures
for different times. The effects of the treatment conditions on the thermomechanical and structural changes of the yarn were
examined by shrinkage, X-ray diffraction and birefringence measurements. With increase in superheated steam temperature, the
crystalline orientation factor and birefringence decreased, whereas crystal size increased. Dry heat treatment had a smaller
effect on shrinkage and structural properties in comparison with superheated steam treatment. The additional shrinkage after
texturing process was investigated. The effect of heat-setting in both media was more significant at 200 °C. The time dependence
of the properties was not linear. 相似文献