A study of the high-speed spinning process for polycaproamide complex yarns

Conclusions -- The basic laws governing the effect of spinning conditions on the properties of PCA yarns have been investigated. It has been shown that in distinction to spinning monofilaments, in high-speed spinning of complex yarns, additional factors appear by use of which it is possible to effectively control the properties of the yarns obtained.-- It has been found that the site of disposition of the aqueous lubricant in the high-speed spinning PCA yarns exerts a fundamentally different action on the breaking elongation of the yarns and on their structure, depending on the linear density and the number of elementary filaments in the complex yarn; however, it does not change the character of this dependence on the breaking strength of the yarn.-- Under otherwise equal conditions, a lower disposition of the lower lubricating device helps in obtaining complex PCA yarns which have a larger breaking strength and a lower elongation.Translated from Khimicheskie Volokna, No. 1, pp. 19–21, January–February, 1991.     

半球头弹体撞击作用下平纹物动态响应的数值模拟

利用数值模拟方法研究了半球头弹体与平纹织物的撞击作用,分析了不同摩擦系数和边界条件时平纹织物的弹道吸能特性.数值模拟结果表明,织物纱线间的摩擦效应对其弹道吸能特性影响相当敏感,增大纱线间的摩擦系数,可以提高织物纱线获得的动能和应变能,增大弹体动能损失量,因此有利于提高织物的抗弹能力.边界条件对弹体动能损失量产生直接影响,当织物四边固定约束时,其弹道吸能特性最佳.     

High-speed spinning of polyester yarns

Conclusions An estimate of the mean lengthwise velocity gradient has been made at 3000 and 4500 m/min); this rises with increase in velocity and degree of stretch, and also as the elementary filaments become thinner.The effect of yarn stretching conditions on change in yarn orientation has been shown for 7, 15, and 25 tex yarns in high-speed spinning.Translated from Khimicheskie Volokna, No. 5, pp. 27–28, September–October, 1985.     

SBS三嵌段共聚物及聚氨酯对涤纶纱线拉伸性能的影响

为进一步研究涤纶纱线的拉伸性能,将聚氨酯及用苯乙烯溶解的苯乙烯-丁二烯-苯乙烯三嵌段共聚物(SBS)对涤纶进行不同工艺处理,并进行拉伸性能测试和结果分析。结果表明:随整理液质量分数的增加,处理后纱线的断裂强力、断裂伸长率、断裂功均呈现先增后减趋势,但断裂强度较原纱均有所降低,而且聚氨酯整理后纱线的断裂强度较SBS整理的下降程度更大。对于纱线断裂强力、伸长率及断裂功的提高,聚氨酯整理效果优于SBS,而对于断裂比功,SBS的整理效果优于聚氨酯。     

Modification of nylon 6 with organochlorosilanes. II. Physical properties

The physical properties of nylon 6 yarn treated with dimethyldichlorosilane (DMCS) and vinylmethyldichlorosilane (VMCS) in nitrogen atmosphere or air in the presence and absence of an amine have been compared with those of ether-extracted parent yarn. Treatment with DMCS in nitrogen resulted in marginal improvement in breaking stress, considerable increase in breaking elongation, and elastic behavior, whereas initial modulus was decreased. A decrease in density, birefringence, and moisture regain with increase in per cent weight gain was observed. Mechanical damping was decreased considerably up to an optimum weight gain after which it was increased. Thermal properties were also determined, and results are discussed in relation to mechanical properties. The results indicate that the overall thermal stability has decreased in the chemically treated yarns. Treatment with organochlorosilanes in the presence of air results in a chain-scission reaction and a decrease in mechanical properties.     

Effect of Air-Jet Texturing on Adhesion Behaviour of Technical Polyester Yarns to Rubber

Air-jet texturing of technical polyester yarns was performed in order to improve its adhesion to rubber. The air-jet texturing parameters were selected with great care to minimize the mechanical loss. H-adhesion tests were used to characterize the adhesion of the yarns to rubber. A significant increase in the adhesion of dimensionally stable polyethylene terephthalate yarn, textured with an overfeed level of 15% (DSPET15), was recorded, while a decrease in the adhesion of high tenacity polyethylene terephthalate (HTPET) yarn was observed for all overfeed levels. The effects of air-jet texturing on the adhesion of technical polyester yarns were discussed in terms of changes in the yarn geometry and changes on the single fiber surfaces. Changes in the yarn geometry were investigated by optical microscopy studies, while changes on the fiber surface were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) studies. It was observed that air-jet texturing alters both the yarn geometry and the single fiber surfaces, leading to a change in the adhesion to rubber.     

Production,structure and properties of twistless carbon nanotube yarns with a high density sheath

Carbon nanotube web drawn from a vertically aligned carbon nanotube forest is converted into a twistless yarn by a rubbing roller system. The yarn consists of a high packing density sheath with carbon nanotubes lying straight and parallel to the yarn axis and a low density core with many microscopic voids. The rubbing motion causes carbon nanotubes in the surface layers of the yarn to move in opposite directions and consequently large shear strains in the intermediate region tear the partially densified carbon nanotube assembly apart, resulting in the formation of large voids in the yarn core. The specific tensile modulus and sonic velocity of the core-sheath structured, twistless carbon nanotube yarns are significantly higher than that of their corresponding twist-densified yarns. These improvements have been attributed to increased nanotube-to-nanotube contact length in the high packing density sheath and very few carbon nanotubes lying at an angle to the yarn axis.     

Defectiveness of texturized yarns which have a matrix-fibrillar structure

Conclusions The PE content of a matrix-fibrillar yarn spun from a melt of a PCA-PE mixture exerts a significant effect on the formation of defects in this yarn.Yarn defectiveness has been evaluated from acid-resistance; the latter is somewhat reduced for untexturized yarns (as compared with the acid-resistance of yarns from pure PCA) and is considerably reduced for texturized specimens.During the texturizing process, defects of various depths and lengths are formed on the surface of matrix-fibrillar yarns due to breaking off of individual PE fibrils; the intensity of this phenomenon rises with increase in the concentration of PE in the PCA.Translated from Khimicheskie Volokna, No. 6, pp. 45–46, November–December, 1986.     

The effect of internal temperature rise on the tensile behavior of polymeric materials at subambient temperatures

The tensile properties of nylon, Dacron, and Nomex yarn are given at liquid helium temperatures, ?450°F, and at two strain rates, 1.67 and 3000%/sec. The data are compared to similar results obtained at ?320°, ?109°, and 70°F. A theoretical analysis of the thermodynamics of straining under both isothermal and adiabatic conditions is presented, and theoretical maximum temperature rises occurring within both adiabatically and isothermally strained yarns are given for a range of subambient test temperatures. The initial modulus of the yarns increases, the tenacity increases, and the breaking elongation decreases with decreasing temperature at the lower rate of straining. However, at the higher rate of straining, although the initial modulus of the yarns at ?450°F is considerably greater than the modulus at ?320°F, the nylon yarn shows a lower breaking load and greater breaking elongation at ?450°F than at ?320°F. The Dacron follows the expected trend with the breaking load higher and the breaking elongation smaller at ?450°F than at ?320°F. The Nomex has a lower breaking load, but its breaking elongation is also lower at ?450°F than at ?320°F. The calculated yarn internal temperature rises are sufficient to explain these differences in the stress–strain behavior of the yarns.     

Optimization of Open-end Rotor Spinning Frame Parameter and Estimation of Relevant Quality Characteristics

The high-cleaning Lyocell fibers are used to spin the Ne 32 yarns for an open-end rotor spinning frame. The optimal processing parameters were obtained in demonstrating output speed, stretching roller speed, feed speed and rotor revolution. The quality characteristics, such as yarn count, strength, elongation and Um (%), are far beyond the rating standard of the combed yarn. No yarn breaking for continuous spinning during the experimental confirmation. The result presents lower yarn breaking rate and maintains stabilized output status of spinning conditions. The back propagation neural network was employed for learning, forecast and verification of the processing parameters.     

Complex evaluation of the quality and serviceability of yarns during preparation and processing processes

Conclusions -- The basic factors and principles which determine the stability of processes of preparing and processing yarns have been examined. It has been shown that it is advisable to use the figure for the mean length of a break-free yarn section as a general characteristic for technological stability for yarns of various types and various processes. -- Application of reliability theory shows that the mechanical properties of yarns (load-bearing ability) and technological reserve in mechanical properties (reserve coefficient) have basic importance to ensure stability of technological processes. Thereupon, one should take into account the change in yarn properties under the effect of external actions under the conditions of technological processes. -- The effect of structure heterogeneity and yarn defectiveness on nonuniformity in properties and yarn serviceability in technological processes has been analyzed. -- Various methods of predicting yarn serviceability which are based on evaluating both their breaking characteristics and also of complex quality criteria have been generalized and analyzed. -- New criteria for predicting the serviceability of yarns have been proposed: the scale coefficients of the breaking characteristics for the case of single stretching actions and a complex durability figure for the case of repeated actions of stretching and bending with abrasion. These criteria are particularly important for evaluating the serviceability of yarns with specific mechanical properties. -- The connection between complex quality criteria and the serviceability of yarns with the stability of technological processes (breakage) and the quality of the textile materials obtained has been examined. The author remembers with thanks Prof. A. B. Pakshver, who has helped greatly in discussion of questions about the serviceability of yarns in processes of preparing and processing them. Translated from Khimicheskie Volokna, No. 2, pp. 45–46, March–April, 1991.     

二醋酯长丝复合空气变形纱的性能比较

采用5种不同83．3 dtex合纤长丝作芯丝,分别与177．34 dtex二醋酯长丝进行复合空气变形加工, 分析了不同芯丝对变形纱的结构及其性能的影响。结果表明,复合变形纱的强伸性能和沸水收缩率主要由其芯丝决定;5种芯丝中,以PFT FDY作芯丝时,复合空变纱的丝圈稳定性最好,结构膨松性良好、断裂强度较高,断裂伸长率、2 mm高度毛羽数和成纱外观均匀性居中,但沸水收缩率偏大。     

Shape memory polyurethane-based electrospun yarns for thermo-responsive actuation

Electrospun nanofibrous yarns of shape memory polyurethane (SMPU)-based nanofibers were successfully prepared. The electrospun yarns were analyzed to assess the dependence of mechanical and shape memory properties on the yarn twist angle. The yarn with a 60° twist angle has high compactness and density, leading to increased tensile strength, elastic modulus, and strain energy. In addition, this yarn shows a significant improvement in the shape memory recovery stress compared with the non-twisted SMPU nanofibers. Moreover, thermal stimuli allowed for the 60° twisted yarn to lift a load that is 103 times heavier than itself. This yarn had a shape recovery stress of 0.61 MPa and generated a 7.95 mJ recovery energy. The results suggest the electrospun yarns could be used as actuators and sensing devices in the medical and biological fields.     

热处理对牛奶蛋白纤维纱性能的影响

研究了热处理对牛奶蛋白纤维纱性能的影响,包括热收缩、白度和黄度、断裂强度和断裂伸长率、失重率。通过对实验结果的分析可以发现,当温度低于150℃时,牛奶蛋白纤维纱的性能变化较小;当温度高于150℃时,牛奶蛋白纤维纱的性能变化显著,说明牛奶蛋白纤维纱在后整理加工中热处理温度应该低于150℃,以减少对牛奶蛋白纱性能的影响。     

Relationship between set and bulk of package–dyed wool yarns

The loss of bulk in hand–knitting yarns as a result of package dyeing has been investigated. Simulated dyeing of packages, prepared with and without axial compression, has revealed a correlation between the bulk of the relaxed dyed yarns and the permanent longitudinal set imparted to the yarns. The strain in the yarn in the wet package, and hence the longitudinal set, is related to the hygral expansion of the yarn and the strain imposed on the yarn during winding of the package. The role of axial compression of the package in determining loss of bulk is also considered. Finally it is shown that by adding reagents to the dyebath that inhibit the setting reaction, the loss of bulk can be markedly decreased, provided also that the yarns are fully relaxed after being dyed.     

Structure and properties of dyed polypropylene yarn containing an addition of chemically colored low-molecular polycaproamide

Conclusions The thermal properties of PP yarns have been studied by determining their weight loss on heating. It has been shown that, by comparison with unmodified PP yarn, yarns containing an addition of chemically dyed LMPCA have improved thermal stability.Addition of chemically dyed LMPCA in the spinning of PP yarn leads to an increase in mean crystallinity and a decrease in the average size of yarn crystallites after jet stretch. The existence of two morphological forms of supermolecular structure has been shown by the electron microscopy method: spherulitic and oriented along the yarn axis.Translated from Khimicheskie Volokna, No. 6, pp. 20–21, November–December, 1986.     

Improvement of physico-mechanical properties of jute yarn by photografting with 3-(trimethoxysilyl) propylmethacrylate

Jute yarns were treated with an alkoxy silane monomer 3-(trimethoxysilyl) propylmethacrylate under UV radiation. The monomer concentration and radiation intensity were optimized with respect to the extent of grafting and mechanical properties of the grafted (silanized) jute yarn. The enhanced tensile strength by 159%, elongation-at-break (237%) and polymer grafting (26.2%) were observed when the yarn was treated at 30 wt% silane in methanol under UV radiation for 30 min. The surfaces of both treated and untreated jute yarns were characterized by X-ray photoelectron spectroscopy (XPS), Fourier-Transform Infrared Spectroscopy (FTIR) and Environmental Scanning Electron Microscopy (ESEM) and it was concluded that the silane reacted or deposited on jute surface as a result of UV radiation. Water uptake and degradation properties of untreated and silanized jute yarn were studied in various conditions such as simulated weathering and in soil containing 25% water. The silanized jute yarn showed lesser water uptake as well as less weight loss and mechanical properties as compared to virgin samples.     

Elastic Recovery at Static Loading and Impact Indentations in MgF2

The extent of elastic recovery at spherical indentations in MgF₂ indented by static and impact loads was analyzed. The fraction of the indentation depth that was recovered decreased with increasing static load. Similar results were observed for impact loads. The kinetic energy losses increased with a velocity exponent of 2.61 despite substantial variations in the contributions of various loss mechanisms over the range of velocities for which measurements were made. Apparently, the losses are partitioned among the various loss mechanisms that derive their energy from the elastic field.     

Synthesis,photodegradation, and energy transfer in a series of poly(ethylene terephthalate–co–2,6-naphthalenedicarboxylate) copolymers

Triplet–triplet energy transfer has been shown to occur from poly(ethylene terephthalate) (PET) units to the 2,6-naphthalenedicarboxylate (2,6-ND) monomer units in a series of poly(ethylene terephthalate–co–2,6-naphthalenedicarboxylate) (PET–2,6-ND) copolymers, as filament yarns, by an exchange mechanism at 77°K. The radius of the “quenching sphere” has been calculated to be 19.7 Å, indicating the presence of triplet energy migration. Photostabilization was observed in the copolymer yarns with the concentration of the monomer dimethyl 2,6-naphthalenedicarboxylate (2,6-DMN) at or above 2 mol %; the rate of phototendering in an air atmosphere was shown to decrease from 2.0 × 10^?19% breaking strength loss/quantum absorbed/cm² in the homopolymer PET to 0.7 × 10^?19% breaking strength loss/quantum absorbed/cm² in the copolymer yarns. The photophysical processes in the monomers, dimethyl terephthalate and 2,6-DMN, were examined by absorption and luminescence studies. The lowest excited singlet and triplet in both monomers were identified to be the ¹(π, π^*) and ³(π, π^*) states, respectively. The phosphorescence of PET was shown to originate from a ³(π, π^*) state, while the complex fluorescence spectrum may arise from some oriented aggregates in the polymer matrix. In copolymer yarns, only the fluorescence emission from the 2,6-ND monomer units at 380 nm was observed. The phosphorescence spectra of the copolymer yarns showed phosphorescence emissions from the PET and 2,6-ND monomer units; in addition, delayed fluorescence from the 2,6-ND monomer was also observed.