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.     

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.     

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.     

930dtex锦纶66工业丝拉伸工艺的研究

研究拉伸比对930dtex锦纶66工业丝物理性能的影响,并确定轮胎浸胶帘布用的930dtex锦纶66工业丝生产拉伸比。结果表明,930dtex锦纶66工业丝线密度与拉仲比无明显相关性,断裂强力和卷绕张力与拉伸比呈正线性关系;定负荷伸长率、干热收缩率与拉伸比之间呈抛物线关系;断裂伸长率与拉伸比之间呈负线性关系。轮胎浸胶帘布用的930dtex锦纶66工业丝生产时合适的拉伸比为4．0～6．0,浸胶帘布性能满足标准要求。     

Breaking energies of a nylon series subjected to high-speed transverse impact

In a study of the transient behavior of a series of nylon 6/6 yarns differing systematically in mechanical properties, the effects of high-speed, transverse missile impact upon yarn specimens were observed by high-speed photography. The loss in missile kinetic energy was determined directly from the reduction in missile velocity and was studied as a function of yarn tenacity and missile impact velocity. The shape of the missile energy loss curves was due to the partition of missile energy into yarn kinetic energy and yarn strain energy. The missile energy losses and yarn dynamic breaking strains were compared to static breaking energies and breaking strains for these yarns. The observed trends are discussed in terms of the differing yarn tenacities and test rates.     

Effect of spinning speed on the structure and physical properties of filament yarns produced from used PET bottles

In the previous work (S. Kiantash, MS Thesis, Amirkabir University of Technology, Textile Engineering Department, Tehran, Iran, 2002), the possibility of producing filament yarns from used PET bottles was investigated and the production was successfully carried out. To improve physical properties and to have a detailed understanding of the molecular structure, spinning variables such as the take‐up speed (one of the most influencing factors) should be varied and studied. In the present work, continuous filament yarns from virgin PET chips and used PET bottles were produced at the two take‐up speeds of 2500 and 3000 m/min. Optical birefringence, crystallinity (obtained from three methods including density, calorimetry, and FTIR), tenacity, breaking elongation, initial modulus, and shrinkage of yarns were measured and compared. Optical birefringence and crystallinity (obtained from all three methods) of used samples show higher values compared with those of virgin samples produced at both take‐up speeds. Consequently, the tenacity of used samples is higher and breaking elongation is lower. Generally, samples having bigger crystallinity present higher initial modulus and smaller shrinkage. However, results of initial modulus and shrinkage do not correspond to this assumption. As it was predicted, increasing the take‐up speed resulted in an increase in the optical birefringence, crystallinity, tenacity, and initial modulus and a reduction in the breaking elongation of both virgin and used samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3972–3975, 2007     

Structure–property relationship for poly(lactic acid) (PLA) filaments: physical,thermomechanical and shape memory characterization

Physical, thermomechanical, and shape memory properties of two different samples of poly(lactic acid) (PLA) multifilament yarns were determined using various complementary techniques. The birefringence and crystalline fraction of one sample was higher than the other filaments sample indicating higher molecular orientation and compactness. For both filaments, two distinct morphological features with different sizes in the order of few nanometers (less than 50 nm) were found using AFM and SAXS techniques. The glass transition temperature (T_g) of the samples were ranged from 61 °C to 76 °C depends on the sample and the methods of measurement. Partial storage modulus (E′) increase above T_gas well as additional small peak in loss modulus (E″) of the lower crystallinity sample was assigned to recrystallization. The multiple overlapped peaks in the E″ and tan δ curves and subsequent crystallization along with exothermic peak right after T_g suggests the existence of both relaxed and oriented amorphous regions. The rigid crystalline regions prevented the shrinkage and enhanced dimensional stability. Multifilament yarn with higher crystallinity and total molecular orientation showed higher modulus (both dynamic and static) and strength and lower elongation at break. The oriented non-crystalline regions in the multifilament yarn sample led to moderate modulus and strength along with high elongation at break. The shape recovery of both samples with different structural parameters stayed almost constant (~50 %) upon the deformation temperature rise.     

Fabrication of continuous nanofiber yarn using novel multi‐nozzle bubble electrospinning

A novel multi‐nozzle bubble electrospinning apparatus, including spinning unit, metering pump, constant flow pump, metal funnel and yarn winder, was designed for the preparation of continuous twisted polyacrylonitrile nanofiber yarns, and the principle of nanofiber yarn spinning was studied. An innovative spinning unit consisting of nozzle and air chamber was used to improve the production of nanofibers. Double conjugate electrospinning was developed using two pairs of oppositely charged spinning units to neutralize the charges. The effects of applied voltage, air flow rate, overall solution flow rate and funnel rotary speed on the fiber diameter, production rate and mechanical properties of the nanofiber yarns were analyzed. Nanofibers could be aggregated stably and bundled continuously, then twisted into nanofiber yarns uniformly at an applied voltage of 34 kV, air flow rate of 1200 mL min^?1 and overall solution flow rate of 32 mL h^?1. With an increase in the funnel rotary speed, the twist angle of the nanofiber yarns gradually increased when the take‐up speed was constant. The yarn tensile strength and elongation at break showed an increasing trend with increasing twist angle. Nanofiber yarns obtained using this novel method could be produced at a rate from 2.189 to 3.227 g h^?1 with yarn diameters ranging from 200 to 386 µm. Nanofiber yarns with a twist angle of 49.7° showed a tensile strength of 0.592 cN dtex^?1 and an elongation at break of 65.7%. © 2013 Society of Chemical Industry     

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。     

Morphological and mechanical properties of drawn poly(l‐lactide) electrospun twisted yarns

In this study, the continuous twisted PLLA yarns were produced using an electrospinning device consists of two oppositely charged nozzles. The electrospinning process was performed at different twist rates. The electrospun twisted yarns were drawn at different extension ratios of 50% and 100% and their morphological and mechanical properties of post‐drawn yarns were investigated. The morphological studies at all twist rates shown that uniform and smooth fibers without any bead were formed. Increasing the twist rate up to 240 rpm resulted to a decrease in the average diameter of the fibers in the yarn structure. After uniaxially drawing of the yarns, the average diameter of fibers and thus the yarn diameter decreased. The post‐drawing process enhanced the crystallinity of the fibers in the yarn structure. Furthermore, by increasing the extension ratio, the tensile strength and modulus of yarns increased, while the elongation at break (%) decreased. POLYM. ENG. SCI., 58:1091–1096, 2018. © 2017 Society of Plastics Engineers     

Monitoring of degradation of thermally aged nylon 6,6. II. Pyrolysis–gas chromatography

Pyrolysis–gas chromatography was used as an analytical method to evaluated the extent of chemical changes that occur in aged yarns and to demonstrate any correlation between measured physical properties and pyrolysis products. Nylon 6,6 yarn samples (2.5–3.0 mg) that were control-degraded as a function of humidity, temperature, and time were pyrolyzed at 500°C and chromatographed on a Graphpac AT-1000 column. The peak heights of pyrolysis products unique to the degraded material were correlated with measured tensile strength loss (?5 to ?75%) of the yarns. Linear relationships were found for several of the products, one of which was identified as caprolactam. Significant changes in the pyrograms were observed in nylon with tensile strength losses of 5% or less.     

Structure changes during tensile deformation and mechanical properties of a twisted carbon nanotube yarn

The small-angle X-ray scattering measurements during tensile deformation have been performed for studying the structure and mechanical property relationships of twisted carbon nanotube (CNT) yarns. The tensile strength distribution and the diameter changes during tensile deformation have also been measured. The orientation distribution of the CNTs in the yarn has been determined and its changes during tensile deformation have been related to the variation of the tensile modulus with the twist angle. The tensile modulus and Poisson’s ratio of the yarns decreased with increasing twist angle, whereas the tensile strength of the yarn showed a maximum at the twist angle of 25°. At this twist angle, the distribution width of the tensile strength was minimum indicating the higher uniformity of the yarn structure.     

受阻胺抗氧剂对PA6工业丝热氧老化性能的影响

通过尼龙6(PA6)工业丝和添加质量分数0.5%的受阻胺抗氧剂N,N'-二(2-萘基)对苯二胺(DNP)的尼龙6(PA6-DNP)工业丝的热性能和在热氧化过程中的力学性能的对比,研究了DNP对PA6工业丝的性能影响.结果表明:DNP不改变PA6工业丝的熔融温度,但会引起晶型的变化,对在氮气氛围下的热分解影响不大,对氧气...     

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.     

Mechanische Eigenschaften von Polyesterfasern bei kurzzeitiger Zugbeanspruchung, 2. Verformungsgeschwindigkeitsabhängige Kraft-Dehnungs-Diagramme von Polyester-Multifilamentgarn

Polyethylene terephthalate (PETP) multifilament yarns with different thermal history were used as testing materials. The stress-strain curves for strain rates from 0.1 up to 100 000%/s show that the maximum tensile force increases and the elongation decreases with increasing strain rate. However, there are differences for yarns with different thermal history. So a free of stress treated yarn shows less change of the maximum tensile force with increasing strain rate than a yarn treated at the same temperature but under stress. The elongation by the maximum tensile force shows the opposite behaviour. With increasing influence of the elongation rate to the force of rupture the ratio of the maximum tensile force and the relevant elongation increases faster. The initial slope (modulus) of the stress-strain curves of the multifilament yarn increases for all futed stresses and temperatures with the strain rate. The local minimum of the modulus curves shifts to higher modulus with increasing strain rate while the position of the minimum as a function of the elongation remains constant.     

Deformation properties of complex viscose yarns before and after relaxation in water

Conclusions The character of change in deformatic properties of complex viscose yarns — breaking load and elongation — as a function of the magnitude of the work of deformation to break has been established.The suggestion has been made that it is possible to use this dependence to evaluate yarn defectiveness.Translated from Khimicheskie Volokna, No. 6, pp. 43–45, November–December, 1986.     

Effect of the degree of polymerization of cellulose triacetate on the physicomechanical properties of yarns

Conclusions The dependence of the relative breaking load and elongation at break of cellulose triacetate yarns and the resistance to abrasion and to repeated bending on specific viscosity of the polymer have been investigated.On increase in specific viscosity from 0.32 to 0.41, the fibre strength rises from 9 to 11.4 cN/tex; the resistance to bending, from 1200 to 2000 cycles; the resistance to abrasion, from 1000 to 8000 cycles. The elongation at break and resistance to repeated stretching change but little with increase in specific viscosity.Translated from Khimicheskie Volokna, No. 3, pp. 46–47, May–June, 1985.     

网络度对锦纶66工业长丝物理性能及退绕性能的影响

考察了网络度对锦纶66工业长丝物理性能及退绕性能的影响。结果表明,锦纶66工业长丝的线密度、定负荷伸长率指标随网络度的增加而升高,断裂强力、断裂伸长率和干热收缩率指标随网络度的增加而降低;当网络度保持在12～16个/m时,锦纶66工业长丝的退绕性能较好。     

A modeling and experimental study of the influence of twist on the mechanical properties of high‐performance fiber yarns

Little data exist on how twist changes the properties of high‐performance continuous fiber yarns. For this reason, a study was conducted to determine the influence of twist on the strength and stiffness of a variety of high‐performance continuous polymeric fiber yarns. The materials investigated include Kevlar 29®, Kevlar 49®, Kevlar 149®, Vectran HS®, Spectra 900®, and Technora®. Mechanical property tests demonstrated that the initial modulus of a yarn monotonically decreases with increasing twist. A model based on composite theory was developed to elucidate the decrease in the modulus as a function of both the degree of twist and the elastic constants of the fibers. The modulus values predicted by the model have good agreement with those measured by experiment. The radial shear modulus of the fiber, which is difficult to measure, can be derived from the regression parameter of experimental data by the use of the model. Such information should be useful for some specialized applications of fibers, for example, fiber‐reinforced composites. The experimental results show that the strength of these yarns can be improved by a slight twist. A high degree of twist damages the fibers and reduces the tensile strength of the yarn. The elongation to break of the yarns monotonically increases with the degree of twist. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1938–1949, 2000     

1 100 dtex涤纶帘子线直捻机加捻工艺探讨

采用1 100 dtex涤纶工业丝,在K3501型直捻机上加捻生产涤纶帘子线,锭速8 000 r／min,捻度 440 T／m,外纱张力65％,超喂比5％,防叠角(20±1)°,生产的复捻线断裂强力大于145 N,断裂强力及断裂伸长不匀率均小于1％。同两步法加捻相比,产晶质量和经济效益均明显提高。