BCF膨化变形技术探讨

对BCF膨化变形机理和影响BCF卷曲的主要因素进行了探讨。研究结果表明:气流的紊流状态促使进入喷嘴的丝束的各单丝相互分离、开松。在扩张管出口处,高速气流喷射形成的正激波使丝束发生卷曲变形。当膨化器一定时,丝束的卷曲效果与喂入速度、压缩空气压力和温度等因素有关。     

Improvement in the bonding strength of laminated composites by using air‐textured core‐and‐effect glass yarns

Delamination is the most common failure mode in laminated composites due to the reduced strength in the through‐the‐thickness direction. Air‐jet texturing was used to produce bulk and loops in the yarn, which provides more surface contact between the fibers and the resin. The development of core‐and‐effect textured glass yarns and the effect of texturing parameters were presented in the previous article. This article describes the effect of texturing on the mechanical properties including tensile properties, flexure properties, interlaminar shear strength (ILSS) and fracture toughness (Mode I) of glass laminated composites. The composites of plain and twill weave fabrics were developed from both the textured and nontextured yarns. It was observed that the tensile properties decreased and the flexure properties remained unchanged after texturing. However, significant improvement was observed in ILSS and the Mode I fracture toughness of the composites after texturing. The bulkier, loopy structure of the textured yarn provided more surface contact between the fiber and the resin and significantly improved the bonding strength. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

丙纶BCF在热空气变形中的受热过程与物理性质变化

分析了丙纶BCF在热空气变形时的传热情况。对变形管内丝温的理论计算表明:变形管内丝表面和丝芯温度均以相似的规律——近似指数规律变化,丝在变形管内所达到的温度,超过了丝的软化点而低于丝的熔点。另外,还研究了经BCF变形后丙纶部分物理性质的变化情况。     

Improving the bonding strength of laminated composites by optimizing fabric composition

Delamination is the most common failure mode in laminated composites due to the weaker strength in the through‐the‐thickness direction. Air‐jet texturing is used to produce bulk and loops in the yarn which provides more contact surface between fibers and resin. The development and characterization of core‐and‐effect textured glass yarns and the effect of texturing on the mechanical properties of laminated composites were presented in previous papers. This article describes the optimization of textured composites by varying the type and combination of constituent yarns for improving the mechanical properties. Composites with combinations of various textured yarns and non‐textured yarns were made. It was observed that the composites made from fabrics having non‐textured yarn in the warp and core‐and‐effect textured yarn in the weft had the best combination of mechanical properties. They maintained the tensile and flexure properties of composites with non‐textured yarns but had significantly higher interlaminar shear strength. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effect of shrinkage and process parameters on the monitoring of bulk and surface stream temperatures in injection molding via the infrared waveguide method

This paper analyzes for the first time the application of the infrared hollow waveguide method for the remote sensing of the temperature decay of polymer streams during injection molding. The key feature of the infrared procedure employed is its low transmission loss of the thermal energy in the mid and far infrared spectral regions. This particular advantage allows the hollow waveguide device to measure not only the bulk temperature within the polymer, as commercially available full‐core optical fiber instruments do, but also the temperature at the polymer surface. Moreover, the hollow waveguide device is able to measure quite low temperatures, which conventional thermometers cannot do either. Experimental trials have been run on a Husky injection molding press in order to investigate the effect of some process parameters and shrinkage on the bulk and surface temperature decay signals. The results showed a drastic deviation between the kinetic behaviors of the surface and bulk temperature traces throughout the injection cycle. Particularly, it was noticed that the cooling rate of the surface temperature was more affected by part shrinkage than the cooling rate of the bulk temperature. The experimental results showed also that temperatures below 60°C could be reliably measured with reasonable signal‐over‐noise ratio. Polym. Eng. Sci. 44:955–964, 2004.     

Chemical interaction between carbon fibers and surface sizing

Functional groups on the surface of Polyacrylonitrile (PAN)‐based carbon fibers and in fiber surface sizing are likely to react during the curing process of composites, and these reactions could affect the infiltration and adhesion between the carbon fibers and resin. T300B‐3000‐40B fibers and fiber surface sizing were heat‐treated at different temperatures, and the structural changes of both the fiber surface sizing and extracted sizing after heat treatment were investigated by Fourier transform infrared spectroscopy. The results show that the concentration of epoxy groups in both the fiber surface sizing and extracted sizing decreased with increasing heat‐treatment temperature and decreased to zero after treatment at 200°C. The concentration of epoxy groups in the extracted sizing was lower than that of the fiber surface sizing after treatment under the same conditions; this indicated that the rate of reaction between the carbon fibers and fiber surface sizing was higher than the reaction rate of the fiber surface sizing system. X‐ray photoelectron spectroscopy analysis reveals that the content of C? O bonds and activated carbon atoms on the surface of the desized treated carbon fibers was the highest when the heat‐treatment temperature was 150°C; this proved the reaction between the carbon fibers and the fiber surface sizing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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.     

Surface Crystallization and Water Diffusion of Silica Glass Fibers: Causes of Mechanical Strength Degradation

Pristine silica glass fiber is well‐known to become mechanically weaker when heat‐treated in air but the cause of such weakening is not presently known. The time dependence of mechanical degradation of various silica glass fibers containing varying impurity contents were studied in the range from 500°C to 1000°C. Two possible sources of strength degradation were considered: surface crystallization and water diffusion. Surface crystallization kinetics of silica glass fibers were investigated in a wide temperature range, including nanoscale surface nucleation at low temperatures via scanning electron microscopy. From the comparison of the strength degradation, surface crystallization, and water diffusion data in literature, it was concluded that surface crystallization may be responsible for the mechanical weakening observed in silica glass fiber surface during heat‐treatment at temperatures above ~800°C, whereas water diffusion into the glass surface may be responsible for the strength degradation at lower temperatures.     

Computer Simulation of Polyester High‐Speed Thermal Channel Spinning

A mathematical model to describe the thermal channel spinning (TCS) process in PET high‐speed melt‐spinning has been developed. This model, which is based on the spinning process kinematics, includes the effects of acceleration, gravity, and surfacial air friction. It incorporates the constitutive equation of PET polymer, the heat transfer related to the transverse air blowing and, in particular, to a convection and radiation combining procedure in the thermal channel, while taking into account the nonisothermal crystallization kinetics related to temperature and molecular orientation as well as the elongational viscosity of PET polymer connected with temperature, intrinsic viscosity and crystallinity. The developments of crystallinity, molecular orientation and morphological features of high‐speed‐spun PET fiber in the TCS process are investigated at take‐up speeds ranging from 3 600–4 400 m/min and thermal channel temperatures ranging from 160–200°C. The simulated results of this model are compared with the measured crystallinity, diameter, and birefringence of the spun yarn. The “necking point” in the TCS spinline can be predicted by this model.     

Structure of heat-treated Nylon 6 and 6.6 fibers. I. The shrinkage mechanism

Nylon 6 and 6.6 fibers were submitted to thermal annealing in a wide range of temperatures (below and above their glass transition temperatures) under inert atmosphere and slack condition, allowing free shrinkage. The structural changes due to the heat settings were analyzed by several techniques (differential scanning calorimetry analysis, wide- and small-angle X-ray scattering, and birefringence). The results revealed different recrystallization responses of the fibers to the applied thermal annealings and consequently different shrinkage mechanisms. In the recrystallization of the Nylon 6 fibers were involved a generation of nuclei crystallites in the interfibrillar regions, as well as growth and perfection of these new crystallites and preexisting ones. But, recrystallization of the Nylon 6.6 fiber was accompanied only by growth and perfection of the preexisting crystals. The existence of the nuclei crystallites at temperatures of heat treatments above 120°C was the major commanding factor for the Nylon 6 fiber to undergo less shrinkage than the Nylon 6.6 fiber. These very tiny crystallites worked as crosslinking points that would impose restrictions in the mobility of the chains segments, inhibiting subsequent disorientation of the amorphous regions and consequently intense shrinkage, thus resulting in recrystallization in a preferred direction of the fiber axis. The Nylon 6.6 fiber experienced an instantaneous shrinkage at the annealing temperature around 70°C. That was the temperature necessary to release its hydrogen bonds and the starting temperature for presenting its major structural changes, including global disorientation of the amorphous and crystalline regions. Thus, its recrystallization occurred with no preferred orientation. Also, it was suggested that the occurrence of so different shrinkage mechanisms reside in the different crystalline morphology that these fibers originally possessed before the heat treatments. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 441–452, 1998     

PET竹节花色丝的生产技术

简要地介绍一种差别化纤维——竹节花色丝,其生产方法如改变聚合体的组成,添加一些无机化合物,在纺丝时采用异形喷丝板等;也可将纺丝(常规纺或商速纺)得到的原丝(复丝或POY),经后纺的不均匀拉伸或不足拉伸,再经热处理后制取。此外,还可通过变形、合并与包覆等长丝加捻技术来制得。所得竹节花色丝的特性也因生产技术不同而异。     

Preparation of poly(lactic acid) fiber by dry–jet–wet spinning. II. Effect of process parameters on fiber properties

The dry–jet–wet spinning process was employed to spin poly(lactic acid)(PLA) fiber by the phase inversion technique using chloroform and methanol as solvent and nonsolvent, respectively, for PLA. The as spun fiber was subjected to two‐stage hot drawing to study the effect of various process parameters, such as take‐up speed, drawing temperature, and heat‐setting temperature on the fiber structural properties. The take‐up speed had a pronounced influence on the maximum draw ratio of the fiber. The optimum drawing temperature was observed to be 90°C to get a fiber with the tenacity of 0.6 GPa for the draw ratio of 8. The heat‐setting temperature had a pronounced effect on fiber properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3774–3780, 2006     

村田33H加弹机生产涤纶细旦多孔丝技术初探

探讨了在村田33H加弹机上生产167 dtex/288 f涤纶细旦多孔丝的设备改造及加工工艺。结果表明:通过将第一热箱入口端的固定式导丝器改造为旋转导丝器,选择加工速度550 m/min、拉伸倍数1.65、速比1.45、皮圈角115°、热箱温度185~205℃等工艺条件生产涤纶细旦多孔丝,其生产正常,生产过程中无断头,产品满卷率可达92%以上。     

Crystal structure transformations and orientation in crosslinked elastic fibers of an ethylene‐octene copolymer in response to deformation and heat treatment

Crosslinked elastic fibers, made from a low density (0.875 g/cc) ethylene‐octene copolymer, were studied after constrained at 300% elongation and annealed at different temperatures (40–80°C) to simulate conditions encountered in yarn and textile processing. It is surprisingly found that the transition from pseudo hexagonal to orthorhombic structure is much faster under simultaneously constraining and annealing than that without strain. Almost a neat orthorhombic structure can be produced when the fiber is annealed at 60°C. Annealing above 60°C leads to mixed orthorhombic and pseudo‐hexagonal structures. The average melting point increases with an increase in the fraction of orthorhombic phase. It is also surprisingly noted that the simultaneously constraining and annealing of the fiber can produce highly oriented crystals, even annealed at 80°C (above the average melting point of 65°C). The unique effect of annealing under large strain can be attributed to the crosslinking of the fiber, which makes it possible for the fiber to have strong chain orientation (even in molten state) under large strain. The strong chain orientation in melt leads to a faster structural transition from pseudo hexagonal to more stable orthorhombic structure. The strong chain orientation is also very likely the reason why highly oriented crystal and amorphous phases are formed, including the case where the fiber is annealed above melting point. These findings could be leveraged for improving thermal and mechanical properties of the fabrics made with such fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3565–3573, 2013     

Elevated Temperature Strength Enhancement of ZrB2–30 vol% SiC Ceramics by Postsintering Thermal Annealing

The mechanical properties of dense, hot‐pressed ZrB₂–30 vol% SiC ceramics were characterized from room temperature up to 1600°C in air. Specimens were tested as hot‐pressed or after hot‐pressing followed by heat treatment at 1400°C, 1500°C, 1600°C, or 1800°C for 10 h. Annealing at 1400°C resulted in the largest increases in flexure strengths at the highest test temperatures, with strengths of 470 MPa at 1400°C, 385 MPa at 1500°C, and 425 MPa at 1600°C, corresponding to increases of 7%, 8%, and 12% compared to as hot‐pressed ZrB₂–SiC tested at the same temperatures. Thermal treatment at 1500°C resulted in the largest increase in elastic modulus, with values of 270 GPa at 1400°C, 240 GPa at 1500°C, and 120 GPa at 1600°C, which were increases of 6%, 12%, and 18% compared to as hot‐pressed ZrB₂–SiC. Neither ZrB₂ grain size nor SiC cluster size changed for these heat‐treatment temperatures. Microstructural analysis suggested additional phases may have formed during heat treatment and/or dislocation density may have changed. This study demonstrated that thermal annealing may be a useful method for improving the elevated temperature mechanical properties of ZrB₂‐based ceramics.     

Effect of annealing on the structure and properties of polyvinylidene fluoride hollow fiber by melt‐spinning

Polyvinylidene fluoride hollow fibers were prepared by melt‐spinning technique under three spinning temperatures. The effects of annealing treatment on the structure and properties of hollow fiber were studied by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), tensile test, and scanning electron microscopy (SEM) measurements. DSC and WAXD results indicated that the annealing not only produced secondary crystallization but also perfected primary crystallization, and spinning and annealing temperature influenced the crystallinity of hollow fiber: the crystallinity decreased with the increase of spinning temperature; 140°C annealing increased the crystallinity, and hardly influenced the orientation of hollow fiber; above 150°C annealing increased the crystallinity as well, and furthermore had a comparative effect on the orientation. The tensile tests showed that the annealed samples, which did not present the obvious yield point, exhibited characteristics of hard elasticity, and all the hollow fiber had no neck phenomenon. Compared with the annealed sample, the precursor presented a clear yield point. In addition, the annealed samples had a higher break strength and initial modulus by contrast with the precursor, and the 140°C annealed sample showed the smallest break elongation. SEM demonstrated the micro‐fiber structure appeared in surface of drawn sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 935–941, 2007     

Studies on fibers spun from poly(vinyl alcohol‐b‐acrylonitrile) emulsions prepared by ultrasonic technique. II. Properties of the fibers

The moisture content of poly(vinyl alcohol‐b‐acrylonitrile) fibers decreases with an increasing hydrophobic AN content and crystallinity of the fibers; however, the copolymer fiber with 26.94% AN, drawn × 5, and heat‐treated at 200°C has a moisture content value slightly lower than that of commercial PVA fiber, but much higher than that of commercial PAN fiber. The block copolymer fibers have a water‐retention value higher than that of commercial PVA fiber, owing to the presence of voids in these fibers, and have a stronger wicking ability than that of commercial PVA, PAN fibers, and wool and cotton mainly due to the grooved surface and bulk porous morphology of the fibers. The tensile strength of the copolymer fibers with an appropriate AN content are lower than that of commercial PVA fiber, but higher than that of commercial PAN fiber and much higher than that of wool and cotton. The melting temperatures of the copolymer fibers increase with increasing heat‐treatment temperature. The copolymer fibers possess a lower peak cyclizing temperature than that of the PAN fiber and have a higher thermal stability than that of both PVA and PAN fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 989–994, 2001     

X‐ray Absorption Spectroscopy Studies of the Room‐Temperature Ferromagnetic Fe‐Doped 6H–BaTiO3

We investigated the effect of annealing temperature on magnetic properties of 2% and 10% Fe‐doped BaTiO₃. To understand the possible structural differences between samples treated at different annealing temperatures, and to correlate them with the magnetic properties, several characterization techniques, such as X‐ray diffraction and X‐ray absorption spectroscopic methods (XANES and EXAFS) were employed. We found that the 2% Fe‐doped BaTiO₃ pseudocubic perovskite is paramagnetic regardless of the heat‐treatment conditions. Initially paramagnetic 10% Fe‐doped 6H–BaTiO₃, treated at 1250°C, became ferromagnetic after additional annealing at higher temperature. We have crystalographically characterized the cation ordering processes in the 6H–BaTiO₃ that occurred during the high‐temperature annealing. The ferromagnetism that is induced in this stage is most probably associated with the observed diffusion processes but it extrinsic character still cannot be fully disregarded.     

Annealing effect of perfluorosulfonated ionomer membranes on proton conductivity and methanol permeability

Perfluorosulfonated ionomer (PFSI) was synthesized and PFSI membranes were prepared via a solution‐cast method and annealed at different temperatures from 150 to 230°C. The annealing effect on water content, proton conductivity, and methanol permeability were reported and discussed. X‐ray diffraction and small angle X‐ray scattering were used to test the structure of the membranes. It was found that annealing increased the proton conductivity of the membranes because heat‐treatment helped to free the sulfonic groups that were buried in the polymer segments and form more organized ionic clusters. Water content and methanol permeability of the annealed membranes decreased with increasing annealing temperature. Simultaneously, annealing induced more compact chain packing structure, which eventually affected the transport of the proton and methanol through these ionomer membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The Structural Causes of Variations in Dyeing Properties of Terylene Yarn Subjected to Dry and Wet Heat

The dye uptake of Terylene (TCI) subjected to dry and live-steam heat can be characterised by a constant defined as the uptake divided by the square root of time (A/t), as in equations for diffusion. This constant is found to decrease to a minimum with increase in temperature of dry heating and then to increase to a value greater than that for the unheated yarn at high temperatures of preheating. Steam preheating also affects the constant and, at the higher temperatures of steam heating, shows similar tendencies to those found for dry heat but to a less extent. These results were obtained under conditions that allow free shrinkage during dyeing. However, if dyeing is carried out with the material under tension, although the general tendency is the same, the dye-uptake constant is greater than that for the corresponding samples dyed in the absence of tension and is greater than that of the unheated yarn for most of the samples. Measurement of parameters indicative of structural changes in fibres, e.g. moisture regain, density, X-ray orientation and X-ray lateral order, shows that these variations in dyeing properties cannot be explained on the basis of a fringe-micellar network theory of structure. An explanation is advanced which postulates a structure with rod-like morphological units separated by narrow voids, the size, amount and tortuosity of which govern the accessibility of the dye.