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Fiber Coatings (fiber + coating)

Distribution by Scientific Domains

Polymers and Materials Science	53%

Selected Abstracts

Biomimetic solid-phase microextraction to predict body residues and toxicity of chemicals that act by narcosis

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2002
Heather A. Leslie
Abstract A biomimetic extraction technique using solid-phase microextraction (SPME) fibers has been developed for the risk assessment of contaminants with a narcotic mode of action. Our goal is to apply this technique in the future for the prediction of total baseline toxicity of environmental water and effluent samples. Validation of this method requires establishing the relationship between contaminant accumulation and toxicity in biota and accumulation in the surrogate solid phase (the SPME fiber coating). For this purpose, we determined the median lethal concentration (LC50) values for Chironomus riparius midge larvae exposed to two halogenated aromatic compounds separately and measured body residues in the exposed larvae. Solid-phase microextraction fibers with an 85-,m polyacrylate (PA) coating served as the surrogate hydrophobic phase, mimicking the uptake of the compounds by midge larvae. The toxicant concentrations in SPME fibers measured directly by gas chromatography/mass spectrometry (GCMS) or calculated from the SPME fiber,water partition coefficient, KSPME, were related to the toxicant concentrations found in midge larvae. Our results demonstrated that the biomimetic SPME method enables the estimation of body residues in biota and prediction of the degree of baseline toxicity of a water medium. [source]

Enantioselective analysis of mirtazapine, demethylmirtazapine and 8-hydroxy mirtazapine in human urine after solid-phase microextraction

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 2 2010
Fernando José Malagueño de Santana
Abstract A selective and reproducible off-line solid-phase microextraction procedure was developed for the simultaneous enantioselective determination of mirtazapine (MRT), demethylmirtazapine and 8-hydroxymirtazapine in human urine. CE was used for optimization of the extraction procedure whereas LC-MS was used for method validation and application. The influence of important factors in the solid-phase microextraction efficiency is discussed, such as the fiber coatings, extraction time, pH, ionic strength, temperature and desorption time. Before extraction, human urine samples were submitted to enzymatic hydrolysis at 37°C for 16,h. Then, the enzyme was precipitated with trichloroacetic acid and the pH was adjusted to 8 with 1,mol/L pH 11 phosphate buffer solution. In the extraction, the analytes were transferred from the aqueous solution to the polydimethylsiloxane-divinylbenzene fiber coating and then desorbed in methanol. The mean recoveries were 5.4, 1.7 and 1.0% for MRT, demethylmirtazapine and 8-hydroxymirtazapine enantiomers, respectively. The method was linear over the concentration range of 62,1250,ng/mL. The within-day and between-day assay precision and accuracy were lower than 15%. The method was successfully employed in a preliminary cumulative urinary excretion study after administration of racemic MRT to a healthy volunteer. [source]

Analysis of flavor and perfume using an internally cooled coated fiber device

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2007
Yong Chen
Abstract A miniaturized internally cooled coated fiber device was applied for the analysis of flavors and fragrances from various matrices. Its integration with a CTC CombiPAL autosampler enabled high throughput for the analysis of analytes in complex matrices that required simultaneous heating of the matrices and cooling of the fiber coating to achieve high extraction efficiency. It was found that up to ten times increase of extraction efficiencies was observed when the device was used to extract flavor compounds in water, even when limited sample temperatures were used to preserve the integrity of target compounds. The extraction of the flavor compounds in water with the device was reproducible, with RSD not larger than 15%. The lower limits of the linear ranges were in the low ppb range, which was about one order of magnitude smaller than those obtained with the commercialized 100 ,m PDMS fibers. Exhaustive extraction of some perfume ingredients from a complex matrix (shampoo) was realized. All achieved recoveries were not less than 80%. The repeatability of the extraction of the perfume compounds from shampoo was better than 10%. The linear ranges were about 1,3000 ,g/g, and the LOD was about 0.2,1 ,g/g. The automated internally cooled coated fiber device was demonstrated to be a powerful sample preparation tool in flavor and fragrance analysis. [source]

Solid phase microextraction sampling and gas chromatography/mass spectrometry for field detection of the chemical warfare agent O -ethyl S -(2-diisopropylaminoethyl) methylphosphonothiolate (VX)

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 12-13 2003
Gary L. Hook
Abstract A rapid detection method for the chemical warfare nerve agent VX was developed using SPME and gas chromatography/mass spectrometry (GC/MS). Five commercially available SPME fiber coatings were evaluated to determine the optimal fiber coating and conditions for extraction. The use of silanized vials was found to be necessary to limit interaction of the basic tertiary amine component of VX with the acidic silanols present in standard glass vials. The polydimethylsiloxane (PDMS) fiber was ultimately selected for completion of this work with extractions being performed at 50°C. Clothing material was spiked in the laboratory with 1 ,L of neat VX, placed in a sealed vial, and taken into the field for SPME sampling, using optimized conditions studied. GC/MS analysis was also completed in the field using van-mounted instrumentation. With sampling and analysis completed in less than 20.0 minutes, detection of VX contamination was relatively rapid, especially considering the quality of the resulting data. The use of SPME also provides increased safety for the field analysis of VX since it does not require the handling of solvents for sample preparation and samples are not handled directly by the analyst. [source]

Transluzente oxidfaserverstärkte Glasmatrix-Verbundwerkstoffe

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2003
P. Fehling
glass composites; fiber coating; atomic force microscopy; chemical vapour deposition Abstract Das Ziel der Untersuchungen ist die Entwicklung von transparenten Glasmatrix-Kompositen. Neben den mechanischen müssen dazu auch die optischen Eigenschaften der Komponenten aneinander angepaßt werden. Der Einfluß unterschiedlicher Faserbeschichtungen (Bornitrid-, Titandioxid-Einzelbeschichtung oder Bornitrid/Titandioxid-Doppelbeschichtung) auf die mechanischen und optischen Eigenschaften von Nextel 440-Faser verstärktem Glas wird untersucht. Mikromechanische Untersuchungen (push-in Tests) und 3-Punktbiegeversuche erbrachten die größte Verbesserung der Bruchzähigkeit für die Verbunde mit Bornitrid/Titandioxid-doppelbeschichteten Fasern. Die Verbunde mit Bornitrid bzw. Titandioxid Einzelschichten wurden durch Transmissionsmessungen im sichtbaren Spektralbereich charakterisiert. Translucent oxide fiber reinforced glasmatrix composites The aim of the work is the developement of transparent glass matrix composites. Therefore besides the mechanical properties also the optical properties of the components have to be adapted. In this study the influence of different fiber coatings (boron nitride, titanium oxide and a boron nitride/titanium oxide double coating) on the mechanical and optical properties of Nextel 440-fiber reinforced glass was investigated. Micromechanical investigations (push-in-tests) and 3-point-bending tests have shown the best improvement of the fracture toughness for the binary boron nitride/titanium oxide coating. For single coatings of boron nitride or titanium oxide the transparency was characterized by the transmission spectra. [source]

Electrospinning of polyamides with different chain compositions for filtration application

POLYMER ENGINEERING & SCIENCE, Issue 6 2008
Pirjo Heikkilä
Electrospinning of several polyamides, PA6, PA66, PA612, PA614, PA1012, and PA1014, having different chain compositions and lengths of diacid and diamine segments, was demonstrated. Electrospinnability and fiber production rate of these polyamides were evaluated. Electrospun fibers were characterized with regard to their use in air filtration by measuring fiber diameter and filtration efficiency of fiber coating. Longer nonpolar chain segments of higher polyamides could in theory indicate higher dielectricity compared to PA6 and PA66, which would be an advantage in filtration applications. The solubility in polar formic acid and electrospinnability of higher polyamides, on the other hand, were clearly impaired with increased length of chain segments. Hence, PA66 is our best choice, and PA612 and PA6 our second options for commercial filtration applications if fiber electrospinnability, production rate, fiber diameter, and its distribution are concerned. Filtration efficiency of more than 95% of the particles having a diameter of 0.16 ,m and above was achieved with 0.5 g/m2 coating of PA66 nanofibers. Further increase in coating weight mainly increased the pressure drop to an unusable range without a significant further improvement of filtration efficiency. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers. [source]

Genetically Engineered Phage Fibers and Coatings for Antibacterial Applications

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2010
Joan Y. Mao
Abstract Multifunctionality can be imparted to protein-based fibers and coatings via either synthetic or biological approaches. Here, potent antimicrobial functionality of genetically engineered, phage-based fibers and fiber coatings, processed at room temperature, is demonstrated. Facile genetic engineering of the M13 virus (bacteriophage) genome leverages the well-known antibacterial properties of silver ions to kill bacteria. Predominant expression of negatively charged glutamic acid (E3) peptides on the pVIII major coat proteins of M13 bacteriophage enables solution-based, electrostatic binding of silver ions and subsequent reduction to metallic silver along the virus length. Antibacterial fibers of micrometer-scale diameters are constructed from such an E3-modified phage via wet-spinning and glutaraldehyde-crosslinking of the E3-modified viruses. Silverization of the free-standing fibers is confirmed via energy dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy, showing ,0.61,µg cm,1 of silver on E3,Ag fibers. This degree of silverization is threefold greater than that attainable for the unmodified M13,Ag fibers. Conferred bactericidal functionality is determined via live,dead staining and a modified disk-diffusion (Kirby,Bauer) measure of zone of inhibition (ZoI) against Staphylococcus epidermidis and Escherichia coli bacterial strains. Live,dead staining and ZoI distance measurements indicate increased bactericidal activity in the genetically engineered, silverized phage fibers. Coating of Kevlar fibers with silverized E3 phage exhibits antibacterial effects as well, with relatively smaller ZoIs attributable to the lower degree of silver loading attainable in these coatings. Such antimicrobial functionality is amenable to rapid incorporation within fiber-based textiles to reduce risks of infection, biofilm formation, or odor-based detection, with the potential to exploit the additional electronic and thermal conductivity of fully silverized phage fibers and coatings. [source]

Enantioselective analysis of mirtazapine, demethylmirtazapine and 8-hydroxy mirtazapine in human urine after solid-phase microextraction

Solid phase microextraction sampling and gas chromatography/mass spectrometry for field detection of the chemical warfare agent O -ethyl S -(2-diisopropylaminoethyl) methylphosphonothiolate (VX)

Developments in Oxide Fiber Composites

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006
Frank W. Zok
Prospects for revolutionary design of future power generation systems are contingent on the development of durable high-performance ceramic composites. With recent discoveries in materials and manufacturing concepts, composites with all-oxide constituents have emerged as leading candidates, especially for components requiring a long service life in oxidizing environments. Their insertion into engineering systems is imminent. The intent of this article is to present a synopsis of the current understanding of oxide composites as well as to identify outstanding issues that require resolution for successful implementation. Emphasis is directed toward material systems and microstructural concepts that lead to high toughness and long-term durability. These include: the emergence of La monazite and related compounds as fiber-coating materials, the introduction of the porous-matrix concept as an alternative to fiber coatings, and novel strategies for enabling damage tolerance while retaining long-term morphological stability. Additionally, materials and mechanics models that provide insights into material design, morphology evolution, and composite properties are reviewed. [source]

Zirconia,Silica,Carbon Coatings on Ceramic Fibers

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2004
Emmanuel E. Boakye
Precursors for zircon,carbon mixtures were made to coat fibers for ceramic-matrix composites. Precursors were characterized using XRD, TGA, and DTA. Zircon formed from vanadium- or lithium-doped precursors after heat treatments at ,900°C in air, but it did not form at 1200°,1400°C in argon when large amounts of carbon were added. Some precursors were used to coat NextelÔ 720 and Hi-NicalonÔ fibers. The coatings were characterized using SEM and TEM, and coated-fiber tensile strengths were measured. Although zircon formed in powders, only tetragonal-zirconia,silica mixed phases formed in fiber coatings at 1200°C in air. Loss of vanadium oxide flux to the fibers may have caused the lack of conversion to zircon. The strengths of the coated fibers were severely degraded after heat treatment at ,1000°C in air, but not in argon. The coated fibers were compared with zirconia,carbon-coated fibers made using similar methods. Mechanisms for fiber strength degradation are discussed. [source]

Fiber Strength Retention of Lanthanum- and Cerium Monazite-Coated NextelÔ 720

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2004
Emmanuel E. Boakye
NextelÔ 720 fibers were coated with LaPO4 and CePO4 monazite. The coatings were applied using washed and unwashed rhabdophane sols derived from La(NO3)3/(NH4)2HPO4 and a washed sol derived from Ce(NO3)3/H3PO4. The coatings were cured in-line at 900°,1300°C. Multiple coatings were also applied. Fiber strength was retained after coating with washed sols, but not with unwashed sols. These results are consistent with earlier work on LaPO4 monazite fiber coatings derived from La(NO3)3/H3PO4. [source]