Development of polyurethane based conducting nanocomposite fibers via twin screw extrusion

In the present study, conducting nanofillers are incorporated in thermoplastic polyurethane (TPU) to produce nanocomposite fibers through melt compounding route using micro twin screw extruder attached to a fiber drawing device. Nanocomposite fibers using bulk graphite, nanographite and carbon nanofiber were produced using varying amounts of these nanofillers. Metal coated nanographite, new hybrid nanoparticle produced in house, were also used to impart conductivity to the TPU fiber. The process parameters such as processing temperature, mixing time and rpm of the screw have been optimized considering minimum change in TPU bulk properties. It has been found that the nanofillers can be melt mixed safely up to 4 min with the TPU at 180 °C and 100 screw rpm. These mixing conditions give reasonable amount of dispersion. The studies on such fibers in differential scanning calorimetry (DSC) and thermomechanical analyzer (TMA) reveals that the metal coated nanographite particles make the nanocomposite fibers more thermally stable. Both the D. C. conductivity and A. C. impedance of the nanocomposite fibers have reduced significantly even at very low loading of nanofillers, although the conductivity of the produced fibers are in antistatic range (D.C. conductivity ～10^?4 S/m).     

Highly conductive cellulosic nanofibers for efficient water desalination

Electrically conducting nanofibers based on cellulosic materials offer cheap and safe class of materials that can be used for water desalination. In the present work, high conducting cellulose triacetate (CTA) nanofibers containing multiwall carbon nanotubes (MWCNTs) with very low percolation threshold concentration (0.014 wt%) were produced by electrospinning. Unprecedentedly, a hydrophilic ionic liquid consists of 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was used to dissolve CTA producing a solution of 10 wt%. This CTA solution was used to engineer both bare CTA nanofibers and CTA nanofibers impregnated with MWCNT. The fabricated nanofibers were characterized by the field emission-scanning electron microscopy (FE-SEM) and the high-resolution transmission electron microscopy (HR-TEM). Both FE-SEM and HR-TEM images showed that the MWCNTs were inserted and uniformly distributed inside electrospun nanofibers. Furthermore, mechanical properties such as tensile strength of MWCNTs loaded-CTA electrospun nanofibers was significantly improved by up to 280 % and 270 % for the Young modulus, when compared with the bare CTA fibers. In addition, the surface properties as the hydrophilicity of electrospun nanofibers membrane was enhanced due to the presence of MWCNTs. Moreover, the electrical conductivity of MWCNT loaded-CTA electrospun nanofibers was greatly enhanced after the implementation of the MWCNTs inside the CTA fiber. The performance of composite nanofiber for water desalination was examined in a lab-scale classic capacitive deionization (CDI) unit, at different concentrations of salt. The obtained data revealed that the electro-adsorption of anions and cations on the surface of MWCNTs loaded-CTA electrospun nanofibers electrodes were monitored with time and their concentration were decreased progressively with time and reaches equilibrium.     

Preparation and characterization of modified collagen/PAN blending fibers

Graft modification of collagen with acrylonitrile in concentrated aqueous solution of sodium thiocyanate (NaSCN) is developed in this paper. This modification can largely change it’s solubility in water and can be applied in fiber production. Grafting modified collagen is characterized by infrared spectrum and wide angle X-ray diffraction. Wet spinning of PAN fibers containing several content of modified collagen is performed. The tests about these fibers show that breaking strength and sonic orientation decrease as the amount of collagen is raised. The addition of collagen can largely improve the moisture regain of PAN fiber. Micro-appearance of fibers observed under scanning electron microscope (SEM) presents circular cross section and longitudinal grooves on surface, the depth of grooves increases with the increasing draw ratio.     

A Comparative Study of the Thermoplastic Polyurethane/Carbon Nanotube and Natural Rubber/Carbon Nanotube Composites According to Their Mechanical and Electrical Properties

The present study investigated Thermoplastic Polyurethane (TPU), Natural rubber (NR) and their composites in terms of their mechanical and electrical properties for developing wearable stretch sensors. Both TPU and NR were added 2 %wt Multi-wall Carbon Nanotube (MWCNT), then in order to test their influences on TPU/CNT and NR/CNT composites. The result showed that Young’s modulus and Yield point of this experiment were higher than bare TPU and NR, whereas their stress-strain hysteresis loops were bigger than bare TPU and NR. Moreover, the Gauge factor (GF) value of TPU/CNT was much higher than NR/CNT composites at 100 % strain with 7.08. TPU/CNT composites promise to have many applications in the field of stretch sensors with good stability and durability while NR and NR/CNT were easy deformed when the stretch was applied.     

Effects of Chemical Functionalization of MWCNTs on the Structural and Physical Properties of Elastomeric Copolyetherester-based Composite Fibers

Elastomeric copolyetherester (CPEE)-based composite fibers incorporating various neat and functionalized multiwalled carbon nanotubes (MWCNTs) were prepared through a conventional wet-spinning and coagulation process. The influence of functionalized MWCNTs on the morphological features, and the thermal, mechanical properties and electrical conductivity of CPEE/MWCNT (80/20, w/w) composite fibers were investigated. FE-SEM images show that a composite fiber containing poly(ethylene glycol)-functionalized MWCNTs (MWCNT-PEG) has a relatively smooth surface owing to the good dispersion of MWCNT-PEGs within the fiber, whereas composite fibers including pristine MWCNTs (p-MWCNT), acid-functionalized MWCNTs (a-MWCNT), and ethylene glycol-modified MWCNTs (MWCNT-EG) have quite a rough surface morphology owing to the presence of MWCNT aggregates. As a result, the CPEE/MWCNT-PEG composite fiber exhibits noticeably increased thermal and tensile mechanical properties as well as a faster crystallization behavior, which stems from an enhanced interfacial interaction between the CPEE matrix and MWCNT-PEGs.     

Effect of degree of polymerization on the mechanical properties of regenerated cellulose fibers using synthesized 1-allyl-3-methylimidazolium chloride

1-Ally-3-methylimidazolium chloride ([AMIM]Cl) was successfully synthesized and was used as a green spinning solvent for cellulose. The celluloses of various degrees of polymerization (DP) were dissolved in the [AMIM]Cl to obtain 5 % (w/w) cellulose solutions, which were regenerated to cellulose fibers through wet spinning process. Of three different regenerated cellulose fibers with different DPs, a DP of 2,730 was gave the strongest regenerated fiber without drawing having a tensile strength of 177 MPa and an elongation at break of 9.6 % respectively, indicating that celluloses of higher molecular weight can be entangled and oriented more easily. Also maximum draw ratio of the as-spun fibers increased from 1.2 to 1.7 with increasing degree of polymerization leading to a tensile strength and modulus of 207 MPa and 48 GPa, respectively. Particularly the tensile modulus was substantially higher than those of lyocell and high performance viscose fibers of 20 GPa or less. The higher DP of pristine cellulose was critical in increasing the mechanical properties such as tensile strength and elongation at break of the as-spun fibers coupled with higher tensile modulus after drawing.     

Effect of water and fiber length on the mechanical properties of polypropylene matrix composites

This paper presents the results of a current study on polypropylene matrix composites processed by injection, with two different glass fiber lengths and five different volume fractions. Physical and mechanical properties were obtained, namely flexural strength, stiffness modulus and fracture toughness. The mechanical properties of the composites increased significantly with the increase of the fibers volume fraction in agreement with the Counto model. The effect of water immersion time was also analysed. Immersion in water promotes a marked decrease in mechanical properties in the early seven-ten days, and afterwards tends to stabilize. Water causes a decrease of the relative strength which increases with fiber volume fraction and reaches about 29 % and 32 % for 20 % of 4.5 mm fiber length and for 25 % of 12 mm fiber length respectively, after 28 days immersion in water. Fracture toughness increases with fiber volume fraction and is always higher for 12 mm fiber length composites than for 4.5 mm fiber length composites.     

Effect of multi walled carbon nanotube on the crystalline structure of polypropylene fibers

Polypropylene fibers containing varying amounts of multi walled carbon nanotube (MWCNT) have been spun using a conventional melt spinning and drawing apparatus. Changes in morphology and crystalline structure of composite fibers induced by addition of MWCNT were studied by small angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS), Fourier transform infrared spectroscopy (FTIR) and birefringence measurements. The results of SAXS experiments showed an increase in lamellar thickness, long period and crystallinity of the composite fibers in comparison to pure polypropylene fibers. Molecular orientation and helical content of the fibers were increased due to the addition of MWCNT to the polypropylene matrix. WAXS results, being in agreement with the SAXS results, also showed an increase in crystallinity of the composite fibers due to the increase in MWCNT content. This is probably because of nucleating effect of nanotubes in the fiber matrix, causing more crystallization and orientation of molecules to take place around them.     

Composites of polyvinyl alcohol and carbon nanotubes decorated with silver nanoparticles

A simple method to decorate carbon nanotubes (CNTs) with silver nanoparticles was developed to enhance the electrical conductivity of CNTs. The acid-treated CNTs were suspended in the silver acetate solution, ammonia solution was then added, and the CNTs decorated with silver nanoparticles (Ag@CNTs) were produced. The Ag@CNTs were dispersed in polyvinyl alcohol (PVA) to fabricate electrically conducting polymer composites. The electrical, thermal and mechanical properties of the composites were measured. The electrical conductivity of the composites containing 0.8 % (o.w.f.) Ag@CNTs was more than four orders of magnitude higher than those of pristine and functionalized CNTs respectively, which confirmed the effectiveness of the Ag@CNTs as conducting filler. However, the improved electrical conductivity led to somewhat decrease of mechanical properties of PVA/Ag@CNTs composites.     

Development and characterization of MWNTs/Chitosan biocomposite fiber

The Preparation of conductive biocomposite fiber through Carbon nanotubes (CNTs) incorporation into biopolymer matrixes has stimulated much interest for bio-implant applications. The present study focuses on development and characterization of biocomposite fiber composed of chitosan (CHT) as a biopolymer and multiwall carbon nanotubes (MWNTs) as a conductive filler. In term of processing, the most important challenge is to prepare a highly stable dispersion of MWNTs in biopolymer matrix. The hydrodynamic diameter distribution of CNTs in acetic acid solution acquired by dynamic light scattering (DLS).Results demonstrate the supreme stability of CNTs dispersion which is extremely essential for homogenous distribution of CNT in polymeric matrix. Rheological properties of the spinning solution have also been investigated to adjust the viscosity for fiber processing step. A range of viscosity between 2000–8000 cP, has been recorded in different CNT loading. The scanning electron microscopy (SEM) images of the surface and cross sectional area of the fibers reveal the formation of nano-pores after MWNT addition. The tensile strength show a maximum increase of about 33.65 % compared to bare CHT. Also, the measurement of four probe electrical conductivity for different MWNTs loading shows a maximum conductivity of 0.107 S/cm at percolation threshold of 2.89 wt%.     

苎麻主要品质性状相互关系的研究

苎麻纤维细度、细度均匀度、断裂强力、强度、伸长率及结晶度等品质性状是影响苎麻品质及其可纺性的几项主要因素。本文对30个苎麻品种的主要品质性状进行了研究,并利用断裂强力与纤维直径之间的极显著相关性,建立断裂强力依直径的回归方程：y=-1．887＋1．756x。     

The study on the air volume fraction of electrospun nanofiber nonwoven mats

Electrospinning is an efficient method to produce polymer fibers with a diameter range from nanometers to a few microns using an electrically driven jet. Electrospun nanofiber nonwoven fabrics can be applied into different areas with higher air volume fraction, especially applied into textile materials with good warmth retention property. In this article, the air volume fraction in nonwoven mats made of electrospun nanofibers was verified by studying fiber volume fraction in the mats. Then the relationship between fiber volume fraction and fiber diameter was derived, and the fiber volume fraction is in direct ratio to the square of fiber radius. By experimental verification, to get electrospun PAN nanofiber nonwoven mats with high air volume fraction about 99 %, it can fix the polymer concentration on 8 %. The voltage fixed on 20 kV, the tip-to-collector distance on 15 cm. The experiment is in accordance with the theory excellently.     

不同苎麻品种纤维物理性能的差异及相关性的初步研究

比较研究107个不同苎麻品种纤维物理性能，结果表明：单株原麻干重、有效株、断裂功、纤维支数、断裂强力(强度)变异系数较大；单株原麻干重与纤维支数极显著负相关，与断裂强力(强度)显著正相关，与株高极显著正相关；纤维支数与断裂强力(强度)极显著负相关，与断裂伸长(伸长率)极显著负相关；纤维断裂强度(强度)与断裂伸长(伸长率)呈极显著正相关，与断裂功极显著正相关。     

Facile fabrication of carbon nanotubes/polystyrene composite nanofibers for high-performance electromagnetic interference shielding

Polystyrene (PS) composites with nanofibrous structure consisting of multi-walled carbon nanotubes (MWCNTs) with 0-10 wt.% of nanofiller have been fabricated via electrospinning technique. The surface morphology and thermal properties of the composites were evaluated by scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). The SEM analysis of the composite nanofibers samples revealed that the average diameter of the nanofibers increases with increasing MWCNTs content. The resultant MWCNTs/PS composite nanofibers diameters were in the range of 391±63 to 586±132 nm. The thermal stability of composites was increased after addition of MWCNTs to PS matrix. The electrical conductivity of the composites with different weight percentage of MWCNTs was investigated at room temperature. Electrical conductivity of MWCNTs/PS composite nanofiber followed percolation theory having a percolation threshold V _c= 0.45 vol% (~0.75 wt. %) and critical exponent q=1.21. The electrical conductivity and thermal properties confirmed the presence of good dispersion and alignment MWCNTs encapsulated within the electrospun nanofibers. The electromagnetic interference (EMI) shielding effectiveness of the MWCNTs/PS composites was examined in the measurement frequency range of 8.2-12.4 GHz (X-band). The total EMI shielding efficiency of MWCNTs/PS composite nanofibers increased up to 32 dB. The EMI shielding results for MWCNTs/PS composite nanofibers showed that absorption loss was the major shielding mechanism and reflection was the secondary mechanism. The present study has shown the possibility of utilizing MWCNTs/PS composite nanofibers as EMI shielding/absorption materials.     

Morphology and properties of polyacrylonitrile/single wall carbon nanotube composite films

Composite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in DMF subsequent to sonication. The SWNTs in the films are well dispersed as ropes with 20–30 nm thickness. Moreover, AFM surface image of the composite film displays an interwoven fibrous structure of nanotubes which may give rise to conductive passways and lead to high conductivity. The polarized Raman spectroscopy is an ideal characterization technique for identification and the orientation study of SWNT. The well-defined G-peak intensity at 1580 cm⁻¹ shows a dependency on the draw ratio under cross-Nicol. The degree of nanotube orientation in the drawn film was measurable from the sine curve obtained by rotating the drawn film on the plane of cross-Nicol of polarized Raman microscope. The threshold loading of SWNT for electrical conductivity in PAN is found to be lower than 1 wt% in the composite film. The electrical conductivity of the SWNT/PAN composite film decreased with increasing of draw ratio due to the collapse of the interwoven fibrous network of the nanotubes with uniaxial orientation.     

A synergetic immune clonal selection algorithm based multi-objective optimization method for carbon fiber drawing process

Carbon fiber production is a large-scale system which comprises a large number of production processes. Among the various complex production conditions, the drawing process is one of the most influential factors that affect the quality of carbon fiber. How to obtain the fittest process parameters of the drawing process is a typical multi-objective optimization problem. To address the drawbacks of mathematical programming techniques available for solving optimization problems, we propose a new synergetic immune clonal selection algorithm (SICSA) to obtain the optimal process parameters, such as the linear density, strength, and breaking elongation ratio. The main operators of the SICSA are synergetic evolution, clonal operation and non-uniform mutation. The synergetic evolution between populations adopts a “division-parallel-recombination” mode, the clonal operation searches for optimal solutions globally, and the non-uniform mutation explores optimal solutions locally and enhances the diversity of the solutions. As a result, optimal solutions which lead to reasonable distribution of the drawing ratio are obtained. We also compare the proposed SICSA with an immune algorithm and a genetic algorithm for optimizing the parameter in the drawing process. Our results show that the SICSA has the best performance in precision and convergence time. These results can serve as references and provide guidance for real production of carbon fiber.     

Effect of sericin blending on molecular orientation of regenerated silk fiber

The use of regenerated silk fiber is limited due to its inferior mechanical properties in spite of high potential in a wide variety of applications. Many studies have been conducted in order to improve the mechanical properties of the regenerated silk materials, but no one has so far suggested an obvious solution. Meanwhile, some reports showed evidence that structural development of silk protein can be manipulated by physical interactions between silk fibroin (SF) and silk sericin (SS) during the regeneration process, especially in recrystallization process of SF. Such a hypothesis suggests a promising clue to enhance the mechanical properties of silk-based materials. Therefore, in this study, we tried to elucidate how SS can promote developing the molecular chain orientation of SF, resulting in an improvement of mechanical properties of regenerated silk fiber during spinning process. The tensile properties of the regenerated silk fiber were significantly improved compared to those of pure SF fiber when a proper amount of SS was blend with SF; both tenacity and breaking elongation increased by approximately 30 % and 70 % at three fold draw ratio, respectively. Quantitative analysis of X-ray diffraction and Herman’s orientation coefficient confirmed that such an improvement of tensile property was mainly caused by an increase of molecular orientation induced by sericin during the drawing process.     

Data transmission textiles for smart clothing using conducting fibers

In this study, electrical properties and data transmission characteristics of 75D PET/silver composite filaments were measured and analyzed in order to explore the feasibility of “digital textiles” in terms of resistance, resonance frequency, dB loss, and Bandwidth. Those characteristics were measured and compared according to measurement length (10～50 cm) and number of strands (1～10) in order to provide a design guide line for smart clothing. According to the measurement results, electrical characteristics of conducting fiber can be enhanced by increasing the number of fiber strand. It was also demonstrated that multiple resonances could occur from conducting fiber when the fiber lengths are varied. Finally, it showed the delay time of conducting fiber reached the saturated value when the number of fiber strand exceeded five.     

Mechanical properties and water purification characteristics of natural jute fiber-reinforced non-cement alkali-activated porous vegetation blocks

This study reports the effects of the volume fraction of natural jute fiber and the content of the alkali activator on the physical and mechanical properties, sulfate ion resistance, and water purification characteristics of non-cement porous vegetation blocks. The volume fractions of the natural jute fiber were 0.0, 0.1, and 0.2 %, and the alkali activator was applied by replacing 5, 6, 7, 8, 9, and 10 % by weight of the blast-furnace slag. Void ratio, compressive strength, sulfate resistance, and water purification characteristics were characterized. The results indicate that increasing natural jute fiber and the alkali activator content increased the void ratio and improved compressive strength and sulfate resistance. pH was not affected by natural jute fiber content but increased with alkali activator content. At alkali activator contents of 9–10 %, the observed compressive strength was similar to that of cement blocks, whereas mixes with alkali activator contents of 8–10 % showed similar or greater void ratios than those of cement blocks. The compressive strength of the cement blocks decreased following immersion in sulfate solutions; however, the compressive strength of the mixes with the alkali activator and blast-furnace slag increased following exposure to sulfates. Water purification characteristics were examined by allowing water to filter through the blocks; the non-cement porous vegetation blocks reduced the suspended solids, 5-day biological oxygen demand, chemical oxygen demand, total nitrogen, and total phosphorous in the water by >40 %.     

Enhanced mechanical and thermal properties of carbon fiber composites with polyamide and thermoplastic polyurethane blends

In this article, we demonstrated the preparation of carbon-fiber-reinforced composites using a polyamide 6 (PA6)/thermoplastic polyurethane (TPU) blend, in which the addition of TPU resulted in superior mechanical performances and increased thermal stability. According to various characterization techniques, these results are attributed to an enhanced adhesion and a homogeneous dispersion of long-carbon-fibers (LCFs) with TPU sizing in blended polymer matrix. Above all, dynamic-mechanical thermal analysis (DMTA) measurements clearly show that the dynamic storage modulus (E') of the blend composites is increased by threefold with temperature ranges below and above the glass transition temperature. The presence of LCFs in TPU systems induces effective fiber orientation, exhibiting simultaneous improvements in the tensile strength, flexural strength, and thermal stability.