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Fiber Mats (fiber + mat)

Distribution by Scientific Domains

Polymers and Materials Science	94%

Kinds of Fiber Mats

electrospun fiber mat

Selected Abstracts

A Combinatorial Approach for Colorimetric Differentiation of Organic Solvents Based on Conjugated Polymer-Embedded Electrospun Fibers

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2009
Jaewon Yoon
Abstract A combinatorial approach for the colorimetric differentiation of organic solvents is developed. A polydiacetylene (PDA)-embedded electrospun fiber mat, prepared with aminobutyric acid-derived diacetylene monomer PCDA-ABA 1, displays colorimetric stability when exposed to common organic solvents. In contrast, a fiber mat prepared with the aniline-derived diacetylene PCDA-AN 2 undergoes a solvent-sensitive color transition. Arrays of PDA-embedded microfibers are constructed by electrospinning poly(ethylene oxide) solutions containing various ratios of two diacetylene monomers. Unique color patterns are developed when the conjugated polymer-embedded electrospun fiber arrays are exposed to common organic solvents in a manner which enables direct colorimetric differentiation of the tested solvents. [source]

Fast liquid composite molding simulation of unsaturated flow in dual-scale fiber mats using the imbibition characteristics of a fabric-based unit cell

POLYMER COMPOSITES, Issue 10 2010
Hua Tan
The use of the dual-scale fiber mats in liquid composite molding (LCM) process for making composites parts gives rise to the unsaturated flow during the mold-filling process. The usual approaches for modeling such flows involve using a sink term in the mass balance equation along with the Darcy's law. Sink functions involving complex microflows inside tows with realistic tow geometries have not been attempted in the past because of the problem of high computational costs arising from the coupling of the macroscopic gap flows with the microscopic tow flows. In this study, a new "lumped" sink function is proposed for the isothermal flow simulation, which is a function of the gap pressure, capillary pressure, and tow saturation, and which is estimated without solving for the microscopic tow simulations at each node of the FE mesh in the finite element/control volume algorithm. The sink function is calibrated with the help of the tow microflow simulation in a stand-alone unit cell of the dual-scale fiber mat. This new approach, which does not use any fitting parameters, achieved a good validation against a previous published result on the 1D unsaturated flow in a biaxial stitched mat,satisfactory comparisons of the inlet-pressure history as well as the saturation distributions were achieved. Finally, the unsaturated flow is studied in a car hood-type LCM mold geometry using the code PORE-FLOW© based on the proposed algorithm. POLYM. COMPOS., 31:1790,1807, 2010. © 2010 Society of Plastics Engineers. [source]

Swirl mat, and long discontinuous fiber mat,reinforced polypropylene composites,status and future trends

POLYMER COMPOSITES, Issue 4 2000
J. Karger-Kocsis
Polypropylene (PP) composites with glass and natural fiber mat reinforcement (GMT-PP and NMT-PP, respectively) are widely used in different applications, competing with metallic sheets and thermoset polymer composites. Their production occurs via melt impregnation, slurry deposition and various textile architecturing processes that lead to either consolidated or non-consolidated preforms. These preforms are then converted into final parts by hot pressing. The "traditional" GMT-PP composites are nowadays faced with a great challenge because of the introduction of long fiber reinforced thermoplastic (LFT) composites produced on- or off-line. This paper gives a brief survey on the manufacturing, processing, properties and application of GMT and GMT-like systems and it concludes by describing some of the future trends, especially in the fields of material and process developments. [source]

Investigating the link between pulp mill effluent and endocrine disruption: Attempts to explain the presence of intersex fish in the Wabigoon River, Ontario, Canada

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010
Michael S. Pollock
Abstract The ability of some pulp mill effluents (PME) to act as reproductive and endocrine disrupters in fish is well documented in the literature. However, changes are not always consistent with regard to species, gender, hormones, or reproductive effects. In the present study, the presence of the first intersexed fish that, to our knowledge, has been found in a Canadian river exposed to PME, is reported. A field survey of the Wabigoon River near Dryden, Ontario, in the fall of 2000 found intersexed walleye (Sander vitreus vitreus) with significantly altered hormone levels and reduced gonad size. The Wabigoon River receives discharge from a bleached kraft pulp and paper mill and a municipal wastewater (MWW) plant. It also has historical sediment contamination (wood fiber mats) contributing to extended periods of low dissolved oxygen under low flow, drought conditions. A mesocosm-based partial life cycle test exposing fathead minnows (Pimephales promelas) to reference water, 20% effluent volume to river volume (v/v), 40% (v/v), or 60% (v/v) PME as well as a field survey of the walleye in the Wabigoon River were conducted. The only change in our mesocosm exposure was a decrease in testosterone in males with increasing effluent concentration and vitellogenin induction in males exposed to 60% (v/v) effluent. These results did not reflect the magnitude of endocrine disruption seen in the wild fish survey. Several hypotheses that may explain these discrepancies are proposed. Specifically, evidence is offered from published studies indicating that either hypoxia or MWW, alone or in combination with PME, may explain the discrepancy between our field experiment and the wild fish survey. The present study illustrates the complexities of multistressor receiving environments and the need for the development of cumulative effects assessment approaches. Environ. Toxicol. Chem. 2010;29:952,965. © 2010 SETAC [source]

Electrospun PEG,PLA nanofibrous membrane for sustained release of hydrophilic antibiotics

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2010
Xiuling Xu
Abstract Reported in this study is the successful incorporation of a hydrophilic antibiotic drug, tetracycline hydrochloride (TCH), into electrospun PEG,PLA nanofibrous membrane without loss of its bioactivity. Degradation behavior of the copolymer was studied in vitro. Release behavior of TCH from the electrospun membrane and antimicrobial effects of the TCH-loaded membrane against Staphylococcus aureus culture were investigated. The medicated nanofibrous membrane demonstrated sustained release of TCH over 6 days and was found to be effective in inhibiting growth of S. aureus. In addition, increasing the antibiotic drug content in the electrospun membranes was found to enhance the anti-bacterial effectiveness of the medicated fiber mats. And the combination of mechanical barriers provided by the electrospun biodegradable nanofibrous membranes and their capability of local sustained delivery of antibiotics made these membranes more useful in biomedical applications, particularly as new wound dressings for ulcers caused by diabetes or other diseases, and to provide a better means of treatment for these malignant wounds and ulcers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Preparation of polybenzoxazole fibers via electrospinning and postspun thermal cyclization of polyhydroxyamide

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2008
Steve Lien-Chung Hsu
Abstract Polybenzoxazole (PBO) fibers with a submicron diameter were successfully prepared by electrospinning its precursor, polyhydroxyamide (PHA), solutions to obtain the PHA fibers first, followed by appropriate thermal treatments for cyclization reaction. BisAPAF-IC PHA with two different molecular weights (MWs) were synthesized from a low temperature polymerization of 2,2,-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (BisAPAF) and isophthaloyl chloride (IC). Using dimethylacetamide (DMAc) and tetrahydrofuran (THF), solvent effects on the electrospinnability of PHA solutions were investigated. For balancing the solution properties, it was found that DMAc/THF mixture with a weight ratio of 1/9 was the best cosolvent to prepare smooth PHA fibers; uniform PHA fibers with a diameter of 325,720 nm were obtained by using 20 wt % PHA/(DMAc/THF) solutions. For a fixed PHA concentration, solutions with a lower MW of PHA yielded thinner electrospun fibers under the same electrospinning condition. After obtaining the electrospun BisAPAF-IC PHA fibers, subsequent thermal cyclization up to 350 °C produced the corresponding thermally stable BisAPAF-IC PBO fibers with a diameter of 305,645 nm. The structure of the precursor fibers and the fully cyclized fibers were characterized by FTIR. For the cyclized BisAPAF-IC PBO fibers, thermogravimetric analysis showed a 5% weight loss temperature at 523 °C in nitrogen atmosphere. The interconnected fiber structure in the BisAPAF-IC PBO fiber mats was irrelevant to the curing process, but resulted from the jet merging during the whipping process as revealed by the high speed camera images. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8159,8169, 2008 [source]

Structural, Electrical, Mechanical, and Thermal Properties of Electrospun Poly(lactic acid)/Polyaniline Blend Fibers

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2010
Paulo H. S. Picciani
Abstract Conducting electrospun fiber mats based on PLA and PAni blends were obtained with average diameter values between 87 and 1 006,nm with PAni quantities from 0 to 5.6 wt.-%. Structural characteristics of fiber mats were compared to cast films with the same amount of PAni and studied by SEM, SAXS, and AFM. Thermal properties of fiber mats and cast films were compared by DSC analyses. Mechanical properties of fiber mats were also evaluated. It was found that electrospinning process governs the crystal structure of the fibers and strongly affects fiber properties. New properties of PLA/PAni blends are reported due to the size fiber reduction. [source]

Metastable alumina formation during oxidation of FeCrAl and its suppression by surface treatments

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2005
E. N'Dah
Abstract The influence of various surface treatments of industrial FeCrAl grades was investigated in order to reduce the formation of transition aluminas during thermal oxidation in the 800,950°C temperature range. High temperature gas phase annealing in H2 -H2O mixtures promoted the initial formation of an alpha thin film and no transition alumina formed during subsequent oxidation at lower temperatures, showing very low weight gains compared to non-treated grades. Such a treatment was shown to be efficient for isothermal oxidation in oxygen of laboratory foil specimens but also for cyclic air exposure of fiber mats in near-real operating conditions. Surface modification by application of a slurry TiO2 coating before oxidation was also shown to greatly reduce the amount of transition alumina, observed by X-Ray Diffraction and Laser Induced Optical Spectroscopy. For both treatments, the optimal conditions were determined and the influence on oxidation rate was assessed. [source]

Fast liquid composite molding simulation of unsaturated flow in dual-scale fiber mats using the imbibition characteristics of a fabric-based unit cell

Preparation and properties of nanoparticle and long-fiber-reinforced unsaturated polyester composites

POLYMER COMPOSITES, Issue 7 2009
Gang Zhou
In this study, a new approach was used to prepare polymer composites reinforced by both nanoparticles and continuous fibers. Carbon nanofibers were prebound onto glass fiber mats, and then unsaturated polyester composites were prepared by vacuum-assisted resin transfer molding. Mechanical and thermal properties of these composites were measured and compared with those of the composites synthesized by premixing carbon nanofibers with the polymer resin. Flexural strength and modulus of composites improved with the incorporation of nanoparticles. Specifically, the property improvement was higher in the case of the composites prepared by the new prebound method. It was also found that carbon nanofibers increased the glass transition temperature and reduced the thermal expansion coefficient of unsaturated polyester composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]

Compaction of fiber reinforcements

POLYMER COMPOSITES, Issue 3 2002
Gibson L. Batch
In resin transfer molding, dry fiber reinforcements are compacted as the mold closes before injection of a curable resin matrix. This paper presents experimental data of compaction pressure as a function of fiber volume fraction. Data are presented for woven roving mats, random fiber mats, loose fiber rovings for pultrusion, and uniaxial or biaxial roving mats. These data are fit to a mathematical model derived in an Appendix. Experimental data are also given for six combinations of reinforcements. We use the compaction model of each constituent layer to predict the average volume fraction assuming that fiber layers do not interact. However, we see that most combinations of reinforcements have fiber volume fractions greater than expected at pressures under 50 psi, indicating a synergistic packing between the layers of different composition. [source]

Investigation of unsaturated flow in woven, braided and stitched fiber mats during mold-filling in resin transfer molding

POLYMER COMPOSITES, Issue 4 2001
J. Slade
In Resin Transfer Molding (RPM), which is a process to manufacture polymer composites, the impregnation of fibrous reinforcement In the form of mats by a thermosetting resin is modeled as the flow of a Newtonian liquid through a single length-scale porous medium. While this approach is sufficiently accurate for random fiber-mats, it can lead to appreciable errors when applied to woven, braided, or stitched fiber-mats that contain two length scales. This work investigates the primary factors governing the isothermal unsaturated flow through such dual-scale porous media. Two studies were conducted to better understand this phenomenon: the first experimenatally investigated the flow, while the second theoretically modeled the flow and identified important parameters affecting such a flow with the help of dimensionless analysis. In the first study, one-dimensional constant injection rate experiments were performed using various fiber mats. The unsaturated flow behavior of various mats was characterized using a constant "sink" term in the continuity equation. Results indicated that for a given fiber-mat, the magnitude of the sink effect was a function of the capillary number. In the second study, a numerical model was developed to describe flow through dual-scale preforms in which the two flow domains, the inter- and intra-tow regions, were coupled. We identified a dimensionless number called the sink effect index , that characterizes the magnitude of liquid absorption by the tows and is a function of the relative resistance to flow in the tow and inter-tow regions, and the packing density of the tows. The parametric study of this index with the help of numerical simulations reveals its influence on the flow and identifies the distinct transient and steady-state flow regimes. [source]

Charge storage of electrospun fiber mats of poly(phenylene ether)/polystyrene blends

POLYMER ENGINEERING & SCIENCE, Issue 12 2009
Deliani Lovera
Nonwoven fiber mats composed of poly(phenylene ether) (PPE) and polystyrene (PS) blends were prepared by electrospinning of PPE/PS solutions in a mixture of chloroform and hexafluoroisopropanol. The blends showed higher electrospinnability and led to thinner fibers (200 nm,1.3 ,m) than the pure components, because of a proper balance of electrical conductivity and interaction with the electrospinning solvent. The charge retention of the electrospun fibers was evaluated and related to the blend composition and the electret properties of the components. It was found that the nonwoven mats were able to retain up to 60% of the initial surface potential after several days of annealing at temperatures as high as 140°C, which is markedly higher than the charge retention of corona-charged compact films. The capability of the electrospinning technique, to inject charges into the bulk of the material and to orientate the dipoles of the PPE phase in the field direction at the same time, was related to the good surface potential stability of the PPE/PS electrospun fiber mats. The possibility of creating thin PPE/PS fibers with excellent charge retention capabilities makes these materials ideal candidates for electret filter and sensing applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]

Electric current as a control variable in the electrospinning process

POLYMER ENGINEERING & SCIENCE, Issue 7 2006
Ravikant Samatham
In the electrospinning process submicron-diameter polymer fibers can be produced when a high potential difference is applied to a polymer drop suspended at the tip of a capillary. The electrospinning process is affected by a wide range of parameters, because of which controlling the properties of the fibers is difficult. This is the major hurdle in the development of practical applications of electrospun fibers along with its low productivity. Here we are proposing to use the electric current in the electrospinning process to control the "quality of the fibers". Electrospinning of a solution of polyacrylonitrile in dimethylformamide (PAN/DMF) was done by applying a programmed variable flow rate at different constant voltages. The electric current in the process was measured in real time. Four types of jet regimes were observed, electric current and the morphology of the fibers corresponding to these regimes were analyzed. A relation between the electric current, type of jet and morphology of the fibers has been established. The mechanical properties of electrospun fiber mats were also measured by a tensile testing method. POLYM. ENG. SCI. 46:954,959, 2006. © 2006 Society of Plastics Engineers [source]