Interior Of Fibers Research Articles

High-temperature oxidation behavior of SiBN fibers in air

SiBN fibers are one of the most admirable microwave-transparent reinforced materials for high Mach number aircrafts. Currently, the detailed high-temperature oxidation behavior of SiBN fibers has not been studied yet. In this work, we studied the high-temperature oxidation behavior of SiBN fibers with different boron contents at the temperature range of 1000–1400 °C in air. SiBN fibers started to be oxidized at 1100 °C, with Si3N4 and BN phase oxidized to SiO2 and B2O3, respectively. Due to the gasification and the escape of molten B2O3 at high temperatures, amorphous SiO2 could be remained at the fiber surface. As the fiber further oxidized, the molten B2O3 at the inside may infiltrate into the fiber interior to react with Si3N4, causing the precipitation of hexagonal boron nitride (h-BN) nanoparticles and the formation of SiO2/BN layer. Finally, complex oxidation layers with two distinct concentric sublayers accompanied with two transition sublayers could be formed after the oxidizing treatment.

Effects of C/N ratios on the oxidation resistance of SiCN fibers in air

In this work, the high-temperature oxidation behavior of SiCN fibers with different C/N ratios in air was researched in detail. The SiCN fibers showed a diffusion-controlled oxidation process that obeys the parabolic oxidation law, with the oxidation rate decreased as the C/N ratios decreasing. Although SiCN fibers with lower C/N ratios presented rather lower oxidation rate, they showed a larger tensile strength decrement after oxidizing at high temperatures. This phenomenon was contributed to the enhanced stress concentration by the formation of rough interface between fiber interior and oxidation layer.

The formation of chemical/structural gradients in strong covalent bonded SiBN fibers under active nitrogen atmosphere

In this work, SiBN fibers with chemical/structural gradients under the radial direction were fabricated by one-step treatment at 1700 °C under active nitrogen atmosphere. The formation of chemical gradient should be contributed to the boron atoms diffusion from the fiber interior to the surface, under the driven force of BN bond-breaking in Si–N–B networks to form stable BN bonds in the BNB networks at the fiber surface. Meanwhile, the structural gradients with graded phase separation of Si–N–B networks and crystallization behavior of Si3N4 phase could form under the effect of graded boron content distribution. The SiBN fibers with chemical/structural gradients showed better high-temperature stability due to the possibly synergistic effect of the decomposition resistant of boron-rich surface and the optimization of graded boron distribution. We expect our finding as a universal method to fabricate chemical/structural gradients on other boron-containing multinary ceramics with various shapes.

Sustainable dyeing of nylon fabric with acid dyes in decamethylcyclopentasiloxane (D5) solvent for improving dye uptake and reducing raw material consumption

In this investigation, a solvent dyeing approach was studied to minimize the consumption of water and dyes and to reduce waste effluent by the use of Decamethylcyclopentasiloxane (D5) solvent. To analyze D5 solvent ability to penetrate nylon fiber, XPS analysis was carried out. The feasibility of the use of D5 solvent as dyeing media was also assessed by measuring the effect of D5 processing on fabric chemical, thermal, and crystalline properties by FTIR, TGA, DSC, and XRD analysis. The effect of D5 solvent processing on the mechanical properties of nylon was analyzed by measuring the change in fabric strength and elongation. The basic dyeing procedure for nylon with acid dyes has been developed. It was found that D5 can penetrate the nylon fiber interior and both aqueous as D5 solvent have a similar effect on fabric properties. When nylon fabric was dyed in D5 solvent with acid dyes, 100% dye exhaustion was achieved for all three dyes. By replacing water with D5 solvent as dyeing media for AR249, AB83, and AO67 dyes, the color strength reached 11.44, 25.24, and 19.07 from 7.47, 19.18 and 15.48, respectively. Furthermore, the same D5 bath, without recycling or purification was used successfully in 5 repeated dyeing cycles as no process auxiliaries were added in dyebath. Therefore, this compatibility of D5 with existing acid dye range and dyeing machinery makes it readily applicable for bulk scale production.

Sustainable dyeing of nylon with disperse dyes in Decamethylcyclopentasiloxane waterless dyeing system

Because of the prevailing issue of water scarcity, the application of non-aqueous media Decamethylcyclopentasiloxane (D5) was employed in the chemical fiber dyeing and washing process. Confocal laser scanning microscope (CLSM) and X-ray photoelectron spectroscopy (XPS) analysis have been carried out to analyze the penetration of D5 into the interior of nylon fiber and its distribution in fiber cross-section. The solubility of pure disperse dye in D5 has been measured to check the feasibility of dispersing agent exclusion from dyeing formulation. For developing the solvent dyeing and washing process for nylon, nylon fabric was dyed with pure disperse dyes in D5 solvent and washed with D5 without any process auxiliaries. Findings from CLSM and XPS spectrum showed that D5 can diffuse into the nylon fabric surface with and without the addition of accelerant. And accelerant doesn’t affect D5’s ability to penetrate and uniform distribution within the fiber structure. As compared to aqueous dyeing, the 30 and 43 percent increase in K/S was achieved for azo and anthraquinone dyes by using D5 as dyeing media. Furthermore, more than 99 percent solvent can be recycled or recovered. The level dyeing with commercial dyes under conventional dyeing conditions in D5 solvent dyeing media prove the commercial feasibility of this dyeing technology.

Imaging and quantitative analysis of insecticide in mosquito net fibers using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS).

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis was used to qualitatively and quantitatively assess the distribution of permethrin insecticide on the surfaces and interiors of Olyset long-lasting insecticidal net (LLIN) fibers. Total insecticide content in LLINs has been established using many analytical methods. However, it is important to quantify the bioavailable portion residing on the fiber surfaces for incorporated LLINs. ToF-SIMS is a very surface sensitive technique and can directly image the spatial distribution of permethrin insecticide on the surface of Olyset fibers. Surface permethrin appeared as patchy deposits which were easily removed by acetone and reappeared after several days as interior permethrin migrated (bloomed) from the fiber interior. After a wash/incubation cycle, permethrin deposits were more diffuse and less concentrated than those on the as-received fibers. ToF-SIMS is particularly sensitive to detect the Cl- ion, which is the characteristic ion of permethrin. Ion implantation and quantification of dopants using SIMS is well established in the semiconductor industry. In this study, quantitative depth profiling was carried out using 35Cl- ion implantation to correlate secondary ion yield with permethrin concentration, yielding a limit of detection of 0.051 wt% for permethrin. In some cases, surface concentration differed greatly from the fiber interior (>1 μm below the surface). Two- and three-dimensional mapping of Cl at sub-micrometer resolution showed permethrin to be dissolved throughout the fiber, with about 2 vol% residing in disperse, high-concentration domains. This suggests that these fibers fall into the class of monolithic sustained-release devices. It is expected that ToF-SIMS can be a valuable tool to provide insight into the insecticide release behavior of other LLIN products, both current and future.

Observation of the transformation of silica phytoliths into SiC and SiO2 particles in biomass-derived carbons by using SEM/EDS, Raman spectroscopy, and XRD

Scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction were successfully used to observe the location and morphology of the silica phytoliths in biomass-derived carbons and their transformation into SiC and SiO2 particles at high heat treatment temperatures (HTT). The analyses were conducted in chars derived from the endocarp of babassu coconut (EBC), which naturally contains 1.6 wt% of silica in its mineral matter. It was observed that EBC chars with 500–1200 °C HTT present globular echinate SiO2 phytoliths with sizes of 12–16 μm; these phytoliths are mostly concentrated around the surface of the submillimeter char fibers and also in the carbonaceous char matrix. No phytoliths are found in the interior of the char fibers. At 1200 °C HTT, the phytoliths begin to be rounded, and above 1300 °C HTT, most phytoliths decompose and silicon reacts with carbon-forming nanocrystalline β-SiC particles (~ 35 nm crystallite size). Numerous (tens to hundreds) micro- and sub-micro-amorphous or nanostructured SiO2 particles (with sizes predominantly below 2 µm) are then observed at the sites previously occupied by the phytoliths. Few rounded phytoliths survive at 1400 °C HTT, but disappear at higher HTTs (1600–2000 °C). It is likely that the ensembles of micro- and sub-micro-SiO2 particles observed in many sites correspond to the inner remaining part of the original phytoliths, whose most external SiO2 structures (at and near the surface) decompose and take part in the carbothermal reaction for the formation of SiC.

A multi-layered nerve guidance conduit design adapted to facilitate surgical implantation.

Background and AimsThe gold standard procedure after a severe nerve injury is the nerve autograft, yet this technique has drawbacks. In recent years, progress has been made in the development of artificial nerve guides to replace the autograft, but no device has been able to demonstrate superiority. The present study introduces an adaptable foundation design for peripheral nerve regeneration.MethodsSilk fibroin was electrospun, creating a tri‐layered material with aligned fiber surfaces and a randomly deposited fiber interior. This material was rolled into a micro‐channeled conduit, which was then enveloped by a jacket layer of the same tri‐layered material.ResultsThe proposed implant design succeeds in incorporating various desirable aspects of synthetic nerve guides, while facilitating the surgical implantation process for medical application. The aligned fiber surfaces of the conduit support axon guidance, while the tri‐layered architecture improves its structural integrity compared with a fully aligned fiber material. Moreover, the jacket layer creates a small niche on each end which facilitates surgical implantation. An in vivo study in rats showed that nerve regeneration using this device was comparable to results after direct suture.ConclusionThis proof‐of‐principle study, therefore, advances the development of tissue engineered nerve grafts by creating an optimized guidance conduit design capable of successful nerve regeneration.

Improvement of Anti-wrinkle Properties of Cotton Fabrics Treated with Additives of Neutral Salts

By employing 1,2,3,4-butanetetracarboxylic acid (BTCA) as the finishing agent, SHP as the catalyst and neutral salts NaCl and Na2SO4 as the additives, anti-wrinkle finish of cotton fabrics was carried out here. According to the Donnan equilibrium model and the actions of neutral salts in dyeing process of cellulosic fabrics, NaCl and Na2SO4 should both promote the adsorption of BTCA anions onto the surface of fibers and diffusion into the interior of fibers. Consequently, BTCA would crosslink the interior molecular chains of cellulose, improving the anti-wrinkle properties of treated fabrics. In fact, experimental results confirmed the hypothesis that the two additives of neutral salts indeed both improved wrinkle recovery angle (WRA) of the treated fabrics and the optimal molar ratio of NaCl or Na2SO4 to BTCA was 0.2:1 or 0.3:1, respectively. The neutral salts reduced the dosage of BTCA without decreasing WRA, reducing the manufacturing cost. Besides, the fabrics treated with neutral salts presented good durability. Furthermore, thermogravimetric analysis (TGA), Xray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analyses revealed that neutral salts could catalyze the formation of BTCA anhydride by decreasing hydrogen-bond interactions between BTCA molecules.

A comparison of the twisted and untwisted structures for one-dimensional carbon nanotube assemblies

The way how carbon nanotubes (CNTs) are assembled together determines the utilization efficiency of mechanical property in their macroscopic assembly materials. For one-dimensional (1D) assemblies, CNTs are often assembled under drawing and twisting into a fiber structure with a twist angle. In this study, an untwisted 1D assembly, CNT strip, is introduced, inside which the CNTs are not only aligned but also overall parallel to strip axis. Due to the shielding effect of the twisted fiber surface, the interior of CNT fiber is loosely packed, and the fiber is more stretchable and hard to become stiff. On the contrary, CNT strip with high straightness or undirectionality can utilize the CNT's mechanical property much more efficiently, as reflected by its higher strength and modulus. These insights can guide different applications of CNT fibers and strips in textile.

Sound absorption analysis of castor oil based polyurethane foam with natural fiber

Polyurethane (PU) is one of the most common polymer material used in day today life due to its outstanding features like light weight, cheap in cost, and remarkable sound insulation. PU is extensively used in acoustic and insulation applications because of its porous characteristics. But one of the disadvantages of using foam as the acoustic material is emission of the volatile organic compounds in indoor environments, non-biodegradability and landfill issues. To overcome this important environmental issue of the petrochemical based sound absorbing porous materials it is essential to developing green, cost-effective, efficient and bio degradable porous materials for sound absorption. This paper presents investigations on the acoustical properties of castor oil polyol based kenaf fibre reinforced thermoplastic bio-composites and concepts for highly absorbent material. The results show that castor oil based kenaffibre sample shows good acoustic properties at high frequencies and can be used as an alternative replacement to conventional synthetic fiber interior products

Adding Aluminum Hydroxide to Plant Fibers Using In Situ Precipitation to Improve Heat Resistance

Plant fiber is an environmentally friendly, renewable natural resource. It has several excellent properties such as a low density and high softness. These properties make it an especially good raw material for applications such as paper and construction. However, plant fiber has poor resistance to heat, which limits its application in high temperature conditions. Adding aluminum sulfate solution to plant fiber first, and then adding sodium hydroxide solution enables aluminum hydroxide to be distributed uniformly on the surface and interior of a plant fiber. This modification improves the thermo-stability of the plant fiber. Furthermore, compared with the traditional way of filling, using the fiber added aluminum hydroxide by in situ precipitation to make paper, the strength properties of the paper decreased slightly. By combining in situ precipitation with filling, more aluminum hydroxide could be added to the paper while still maintaining good paper strength and better heat resistance.

Variation of pore structure of organosilicone‐modified skin collagen matrix

ABSTRACTThe pore structure of skin collagen matrix modified by organosilicone alone, combination of organosilicone and chromium respectively, was investigated mainly through nitrogen adsorption, scanning electron microscopy and fractal analysis. The results indicated that increasing the dosage of organosilicone endowed more numbers of uniform smaller pores, increased porosity in modified collagen matrix and improved thermal stability verified by differential scanning calorimeter analysis. A similar trend was observed after incorporating less amount of chromium to organosilicone modification in the process. It can be presumed that a rigid and stable three‐dimensional silica network structure formed in the interior of the collagen fiber plays a role in fixing the collagen molecular chain, conferring improved hydrothermal stability to the skin matrix. The findings are of great significance to explore chrome‐less and further chrome‐free silicone tanning technology, and are helpful to promote sustainable development of the leather industry. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44831.

Nanoparticle functionalised small-core suspended-core fibre - a novel platform for efficient sensing.

Detecting small quantities of specific target molecules is of major importance within bioanalytics for efficient disease diagnostics. One promising sensing approach relies on combining plasmonically-active waveguides with microfluidics yielding an easy-to-use sensing platform. Here we introduce suspended-core fibres containing immobilised plasmonic nanoparticles surrounding the guiding core as a concept for an entirely integrated optofluidic platform for efficient refractive index sensing. Due to the extremely small optical core and the large adjacent microfluidic channels, over two orders of magnitude of nanoparticle coverage densities have been accessed with millimetre-long sample lengths showing refractive index sensitivities of 170 nm/RIU for aqueous analytes where the fibre interior is functionalised by gold nanospheres. Our concept represents a fully integrated optofluidic sensing system demanding small sample volumes and allowing for real-time analyte monitoring, both of which are highly relevant within invasive bioanalytics, particularly within molecular disease diagnostics and environmental science.

Membrane Cholesterol in Skeletal Muscle: A Novel Player in Excitation-Contraction Coupling and Insulin Resistance.

Membrane cholesterol is critical for signaling processes in a variety of tissues. We will address here current evidence supporting an emerging role of cholesterol on excitation-contraction coupling and glucose transport in skeletal muscle. We have centered our review on the transverse tubule system, a complex network of narrow plasma membrane invaginations that propagate membrane depolarization into the fiber interior and allow nutrient delivery into the fibers. We will discuss current evidence showing that transverse tubule membranes have remarkably high cholesterol levels and we will address how modifications of cholesterol content influence excitation-contraction coupling. In addition, we will discuss how membrane cholesterol levels affect glucose transport by modulating the insertion into the membrane of the main insulin-sensitive glucose transporter GLUT4. Finally, we will address how the increased membrane cholesterol levels displayed by obese animals, which also present insulin resistance, affect these two particular skeletal muscle functions.

Preparation and characterization of SiC fibers with diverse electrical resistivity through pyrolysis under reactive atmospheres

Due to their fantastic mechanical and high-temperature resistant properties, SiC fibers with electrical resistivity of different orders of magnitude are of great interest for the fabrication of advanced composites with electromagnetic wave absorbent performance as both structural and functional materials. On the basis of well-developed route to prepare SiC fibers, in this work, we demonstrated a facile strategy to fabricate SiC fibers with electrical resistivity of 10−1–106Ωcm by simply employing hydrogen and ammonia as the reactive atmospheres. The SiC fibers with different electrical resistivity had favorable morphologies, with uniform elemental distribution and stable C/Si ratio towards the fiber interior. Moreover, these fibers exhibited excellent mechanical strength and high temperature performance. Due to the innovative strategy, convenient operation and scalable preparation, the method in this work can be further extended to prepare SiC base fibers with adjustable electrical resistivity from other precursors.

Indigo dyeing and microorganism–polymer interaction

Abstract The applications of natural dyes date back almost to the beginning of the history of humankind and textile dying was one of them. Indigo, a symbol of independence and individualism, called the king of colours and the colour of kings and, also, considered the oldest dye known to man, was the most commonly used blue colouring substance in the world. No other dyestuff has been valued by mankind so widely and for as long as indigo blue. Given the prevalence of the use of natural indigo in textile dyeing over the centuries and today this study was taken to determine the impact of natural indigo dyeing on microbial deterioration of a woollen textile. In order to understand the influence of the dye and the dyeing process on the textile biodeterioration a discussion on the impact of fungal species on the undyed woollen fabric is provided. Although both textiles, i.e., undyed and dyed with indigo, incurred serious damage after being subjected to the activity of microorganisms it was found that the dyeing of a woollen textile with indigo decreased the susceptibility of the dyed textile to microbial deterioration. Moreover, the undertaken studies revealed an unprecedented phenomenon, i.e., an unusual interaction between fungal strain and keratin fibres consisting of penetration of its spores into the fibre interior and subsequent formation of characteristic bulges.

Disease-proportional proteasomal degradation of missense dystrophins

The 427-kDa protein dystrophin is expressed in striated muscle where it physically links the interior of muscle fibers to the extracellular matrix. A range of mutations in the DMD gene encoding dystrophin lead to a severe muscular dystrophy known as Duchenne (DMD) or a typically milder form known as Becker (BMD). Patients with nonsense mutations in dystrophin are specifically targeted by stop codon read-through drugs, whereas out-of-frame deletions and insertions are targeted by exon-skipping therapies. Both treatment strategies are currently in clinical trials. Dystrophin missense mutations, however, cause a wide range of phenotypic severity in patients. The molecular and cellular consequences of such mutations are not well understood, and there are no therapies specifically targeting this genotype. Here, we have modeled two representative missense mutations, L54R and L172H, causing DMD and BMD, respectively, in full-length dystrophin. In vitro, the mutation associated with the mild phenotype (L172H) caused a minor decrease in tertiary stability, whereas the L54R mutation associated with a severe phenotype had a more dramatic effect. When stably expressed in mammalian muscle cells, the mutations caused steady-state decreases in dystrophin protein levels inversely proportional to the tertiary stability and directly caused by proteasomal degradation. Both proteasome inhibitors and heat shock activators were able to increase mutant dystrophin to WT levels, establishing the new cell lines as a platform to screen for potential therapeutics personalized to patients with destabilized dystrophin.

Structural hierarchy and surface morphology of highly drawn ultra high molecular weight polyethylene fibers studied by atomic force microscopy and wide angle X-ray diffraction

The meso/nanostructure of UHMWPE fibers manufactured using different processing conditions is explored through atomic force microscopy (AFM) and wide-angle X-ray diffraction (WAXD). Characteristic dimensions of sub-filament microstructure are quantified at the fiber surface and the fiber interior. These measurements are compared to crystalline parameters determined using WAXD. Observation of junctions between microfibrils suggests the original gel network from which the fiber was drawn remain in the final product. For fibers having undergone greater drawing, the fiber surface reveals the presence of large-scale epitaxial features oriented perpendicular to the direction of drawing. Annealing experiments show that epitaxial structures undergo thickening at temperatures >120 °C. Examining fiber cross-sections reveals a network of microfibrils that appear to undergo consolidation with increased drawing. The evolution of the structural hierarchy of these fibers is discussed in the context of its implications for optimization of processing both fibers and their composites.

A Study on the Degree of Amidoximation of Polyacrylonitrile Fibers and Its Effect on Their Capacity to Adsorb Uranyl Ions

Amidoximation of polyacrylonitrile (PAN) fibers was studied by reacting them with hydroxylamine. The chemical structure, mechanical intensity, and morphologies of PAN and amidoximated PAN (AO-PAN) fibers were evaluated by Fourier transform infrared spectroscopy, tensile tests, dynamic mechanical analysis, and scanning electron microscopy, respectively. A higher degree of amidoximation resulted in a higher conversion ratio (CR) of the nitrile group and a higher density of the amidoxime group, while also reducing the mechanical intensity of the fibers. During amidoximation, a hydrogel layer formed on the fiber surface by bonding with H2O molecules, increasing the diameter of the AO-PAN fibers. The layer thickness increased as the CR of the AO-PAN fibers’ nitrile group was increased. The hydrogel layer decreased the adsorption capability by hindering the diffusion of uranyl ions to the interior of the AO-PAN fibers. Therefore, a CR of about 10.8% would provide an appropriate balance between the mechanical properties and the adsorption capability.