Showing papers on "Fiber published in 2007"

High-performance carbon nanotube fiber.

Abstract: With their impressive individual properties, carbon nanotubes should form high-performance fibers. We explored the roles of nanotube length and structure, fiber density, and nanotube orientation in achieving optimum mechanical properties. We found that carbon nanotube fiber, spun directly and continuously from gas phase as an aerogel, combines high strength and high stiffness (axial elastic modulus), with an energy to breakage (toughness) considerably greater than that of any commercial high-strength fiber. Different levels of carbon nanotube orientation, fiber density, and mechanical properties can be achieved by drawing the aerogel at various winding rates. The mechanical data obtained demonstrate the considerable potential of carbon nanotube assemblies in the quest for maximal mechanical performance. The statistical aspects of the mechanical data reveal the deleterious effect of defects and indicate strategies for future work.

Agents and devices for providing blood clotting functions to wounds

Abstract: Hemostatic agents and devices are made from oxidized cellulose fiber, the oxidized cellulose having a carboxylation content increased by the action of nitrogen dioxide on virgin cellulose fiber A composition may be incorporated into the oxidized cellulose fiber to cause a pharmacological effect on a wound to which the hemostatic agents and devices are applied When applied, the oxidized cellulose fiber causes blood emanating from the wound to clot The oxidized cellulose fiber can either be resorbed into the wound or removed from the wound after healing A hemostatic bandage includes a pad of unwoven oxidized cellulose fibers mounted on a substrate Methods of arresting a flow of blood emanating from a wound using such devices are also disclosed Methods of fabricating oxidized cellulose are also disclosed

Kenaf natural fiber reinforced polypropylene composites: A discussion on manufacturing problems and solutions

Abstract: As industry attempts to lessen the dependence on petroleum based fuels and products there is an increasing need to investigate more environmentally friendly, sustainable materials to replace existing materials. This study focused on the fabrication of kenaf fiber reinforced polypropylene sheets that could be thermoformed for a wide variety of applications with properties that are comparable to existing synthetic composites. The research done in this study has proven the ability to successfully fabricate kenaf–polypropylene natural fiber composites into sheet form. The optimal fabrication method for these materials was determined to be a compression molding process utilizing a layered sifting of a microfine polypropylene powder and chopped kenaf fibers. A fiber content of both 30% and 40% by weight has been proven to provide adequate reinforcement to increase the strength of the polypropylene powder. The use of a coupling agent, 3% Epolene enabled successful fiber–matrix adhesion. The kenaf–PP composites compression molded in this study proved to have superior tensile and flexural strength when compared to other compression molded natural fiber composites such as other kenaf, sisal, and coir reinforced thermoplastics. With the elastic modulus data from testing, it was also possible to compare the economic benefits of using this kenaf composite over other natural fibers and E-glass. The kenaf–maleated polypropylene composites manufactured in this study have a higher Modulus/Cost and a higher specific modulus than sisal, coir, and even E-glass thereby providing an opportunity for replacing existing materials with a higher strength, lower cost alternative that is environmentally friendly.

Satellite cell content is specifically reduced in type II skeletal muscle fibers in the elderly

Abstract: Satellite cells (SC) are essential for skeletal muscle growth and repair. Because sarcopenia is associated with type II muscle fiber atrophy, we hypothesized that SC content is specifically reduced in the type II fibers in the elderly. A total of eight elderly (E; 76 +/- 1 yr) and eight young (Y; 20 +/- 1 yr) healthy males were selected. Muscle biopsies were collected from the vastus lateralis in both legs. ATPase staining and a pax7-antibody were used to determine fiber type-specific SC content (i.e., pax7-positive SC) on serial muscle cross sections. In contrast to the type I fibers, the proportion and mean cross-sectional area of the type II fibers were substantially reduced in E vs. Y. The number of SC per type I fiber was similar in E and Y. However, the number of SC per type II fiber was substantially lower in E vs. Y (0.044 +/- 0.003 vs. 0.080 +/- 0.007; P < 0.01). In addition, in the type II fibers, the number of SC relative to the total number of nuclei and the number of SC per fiber area were also significantly lower in E. This study is the first to show type II fiber atrophy in the elderly to be associated with a fiber type-specific decline in SC content. The latter is evident when SC content is expressed per fiber or per fiber area. The decline in SC content might be an important factor in the etiology of type II muscle fiber atrophy, which accompanies the loss of skeletal muscle with aging.

Electrospinning of Porous Silica Nanofibers Containing Silver Nanoparticles for Catalytic Applications

Abstract: Porous silica nanofibers containing catalytic silver nanoparticles have been synthesized by a new method that combines sol−gel chemistry and electrospinning technique. Tetraethyl orthosilicate (TEOS), poly[3-(trimethoxysily)propyl methacrylate] (PMCM), and silver nitrate (AgNO3) were used as precursors for the production of silica−PMCM hybrid fibers containing AgNO3. Calcination of the hybrid fibers at high temperatures results in porous silica fibers because of thermal decomposition of PMCM polymer and in conversion of AgNO3 to silver nanoparticles. The color of the fiber mats changed from white to dark golden yellow due to the surface plasma resonance of the silver nanoparticles embedded in the fibers. The size and density of the silver particles in the silica fibers could be tuned by varying the size of the fibers, amount of AgNO3 introduced, and the thermal treatment conditions. The silica fibers containing silver particles were characterized with environmental scanning electron microscopy, transmissi...

Injection-molded short hemp fiber/glass fiber-reinforced polypropylene hybrid composites—Mechanical, water absorption and thermal properties

Abstract: Natural fiber-based thermoplastic composites are generally lower in strength performance compared to thermoset composites. However, they have the advantage of design flexibility and recycling possibilities. Hybridization with small amounts of synthetic fibers makes these natural fiber composites more suitable for technical applications such as automotive interior parts. Hemp fiber is one of the important lignocellulosic bast fiber and has been used as reinforcement for industrial applications. This study focused on the performance of injection-molded short hemp fiber and hemp/glass fiber hybrid polypropylene composites. Results showed that hybridization with glass fiber enhanced the performance properties. A value of 101 MPa for flexural strength and 5.5 GPa for the flexural modulus is achieved from a hybrid composite containing 25 wt % of hemp and 15 wt % of glass. Notched Izod impact strength of the hybrid composites exhibited great enhancement (34%). Analysis of fiber length distribution in the composite and fracture surface was performed to study the fiber breakage and fracture mechanism. Thermal properties and resistance to water absorption properties of the hemp fiber composites were improved by hybridization with glass fibers. Overall studies indicated that the short hemp/glass fiber hybrid polypropylene composites are promising candidates for structural applications where high stiffness and thermal resistance is required. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2432–2441, 2007

Development of recycled PET fiber and its application as concrete-reinforcing fiber

Abstract: We describe a method that can be used to produce concrete-reinforcing PET fiber from used PET bottles. Using this method, the concrete and PET fibers are easily mixed at a fiber contents as high as 3%. The primary characteristic of the PET fiber is that it is easy to handle. The issue of concern in the development of PET fiber is its alkali resistance; however, we encountered no problems when using the fiber in normal concrete. The wetting tension of PET was found to be lower than that of PVA but higher than that of PP. No toxic gas was generated during a combustion test of the PET fiber. We describe two example applications: a gateway support at Hishikari Mine, Japan, and the pavement of bush roads.

Corrections to "Limits on the Performance of RF-Over-Fiber Links and Their Impact on Device Design"

Abstract: The authors correct an error in their original article (see ibid., vol.54, no.2, p.906-20, Feb. 2006).

Role of Fiber Diameter in Adhesion and Proliferation of NIH 3T3 Fibroblast on Electrospun Polycaprolactone Scaffolds

Abstract: The goal of the current study was to find the quantitative relationship between electrospun polycaprolactone scaffold fiber diameter and NIH 3T3 fibroblast adhesion and growth kinetics. By varying 3 important process parameters--solution concentration, voltage, and collector screen distance--different average fiber diameters ranging from 117 to 1,647 nm were obtained. Although 117 nm represented the lowest possible fiber diameter obtainable, these fibers had beads in them. An increase in fiber diameter to 428 nm led to uniform fibers without any beads. Fiber distribution pattern was a single mode for all the scaffolds except at the largest-diameter end. The diameter distribution changed from single to bimodal at 1,647 nm, suggesting some instability in the process. It was found that cell adhesion and growth kinetics are significantly affected as a function of fiber diameter. Beaded scaffolds offered the lowest cell adhesion and minimal growth kinetics despite having the lowest average fiber diameter. When uniform fibers were formed and the average fiber was in the nanofiber range (428-1051 nm), cell adhesion and growth kinetics decreased as a function of increasing fiber diameter. Cell adhesion kinetics remained invariant when the average fiber diameter was in the micron range (1,647 nm), whereas cell-growth kinetics were slightly greater than with 900 nm scaffolds. We propose that the uniformness of fibers and the average fiber diameter may play an important role in modulating cellular attachment and proliferation in electrospun tissue engineering scaffolds.

Investigation on process parameters of electrospinning system through orthogonal experimental design

Abstract: Electrospinning is a very simple and versa- tile method of creating polymer-based high-functional and high-performance nanofibers. But most of the investiga- tions are not systematic and describe the electrospinning process without quantitative accuracy. Inconsistent and even opposite results have been reported, which has hin- dered the consistent interpretation of the experiments. Or- thogonal experimental method was used to investigate qualitative and quantitative correlations between fiber characteristics (diameters and morphologies) and the pro- cessing and materials parameters. Uniform fibers can be obtained without any beads by proper selection of the processing parameters, and a lower glass transition tem- perature was observed for electrospun fibers than that of native polymer. Results of statistical analysis showed that significant influences were observed for polymer molecular weight and solution concentration on fiber diameters, and there were significant effects of polymer molecular weight, solution concentration, and solvent system on fiber mor- phologies. Meanwhile, solution concentration and polymer molecular weight, and polymer molecular weight and sol- vent system had obvious interaction effects. Regression analysis revealed quantitative relations of fiber diameters and beads percent, that is, Y1 ¼ 72.8X1 � 8.1X2 þ 138.8, Y2 ¼� 3.2X1 þ 0.4X2 þ 60.5, where Y1 is fiber diameter (nm), Y2 beads percent (%), X1 solution concentration (%, w/w), and X2 polymer molecular weight (kDa). Validation test showed that the experimental values of fiber size and beads percent were in good agreement with the calculated ones. Based on these results, optimal conditions could be obtained for predetermined diameters and morphologies

Preparation and properties of recycled HDPE/natural fiber composites

Abstract: Composites based on recycled high density polyethylene (RHDPE) and natural fibers were made through melt blending and compression molding. The effects of the fibers (wood and bagasse) and coupling agent type/concentration on the composite properties were studied. The use of maleated polyethylene (MAPE), carboxylated polyethylene (CAPE), and titanium-derived mixture (TDM) improved the compatibility between the bagasse fiber and RHDPE, and mechanical properties of the resultant composites compared well with those of virgin HDPE composites. The modulus and impact strength of the composites had maxima with MAPE content increase. The composites had lower crystallization peak temperatures and wider crystalline temperature range than neat RHDPE, and their thermal stability was lower than RHDPE.

Studies on lignocellulosic fibers of Brazil. Part II: Morphology and properties of Brazilian coconut fibers

Abstract: Continuing the studies on the Brazilian lignocellulosic fibers, this paper presents chemical, physical, thermal and mechanical properties of curaua fibers, one of the unique fibers of the country. Stress–strain curves as a function of diameter of the fiber and static mechanical properties as functions of diameter, length of the fiber and as function of strain rate are determined for the first time. It was found that the tensile strength (TS) and Young’s modulus (YM) decrease while % strain at break remained constant as fiber diameter increases; decrease of TS and % strain at break and increase in YM as test length increased and an increase in TS and YM but without any change in % strain at break with increase of strain rate. Density, crystallinity, identification of chemical groups and degradation temperatures of these constituents of the fibers have been determined using pycnometer, X-ray diffraction, FTIR, UV and DTA/DSC instruments respectively. Dynamic mechanical analysis was also carried out, which revealed increase in modulus as the water present in the fiber is removed. All the results are discussed in terms of morphological observations including fractography.

Fabrication and Mechanical Properties of Completely Biodegradable Hemp Fiber Reinforced Polylactic Acid Composites

Abstract: Biodegradable composite materials can be produced by the combination of biodegradable polymers and natural fibers. In this study, a new biodegradable composite of hemp fiber reinforced polylactic acid (PLA) was fabricated using the hot press method. Mechanical properties of composites with different fiber volume fractions were tested. The optimum fiber content was determined according to the test results. Effects of alkali treatment on the fiber surface morphology and the mechanical properties of the composites were investigated. Test results show that the composite with 40% volume fraction of alkali treated fiber has the best mechanical properties. The tensile strength, elastic modulus, and flexural strength of the composite with 40% treated fiber are 54.6 MPa, 8.5 Gpa, and 112.7 MPa respectively, which are much higher than those of PLA alone. The composites have lower densities, which were measured to be from 1.19 g/cm3 to 1.25 g/cm3. Specific strengths were also calculated. Surface morphologies of fibe...

Electroactivate shape-memory polymer filled with nanocarbon particles and short carbon fibers

Abstract: In addition to the fabrication of shape-memory thermoset polymer nanocomposites filled with conductive nanoparticles and fiber fillers, this paper is focused on factors which would influence the electrical property of this type of material. It is shown that the particulate additives are dispersed homogeneously within the matrix and served as interconnections between the fibers, while the fibrous additives act as long distance charge transporter by forming local conductive paths. The electrical conductivity of the nanocomposite which contains 5wt% carbon nanoparticles and 2wt% short carbon fiber is 2.32S∕cm by four-point van der Pauw method, and can be induced by 24V voltages.

Development and effect of alkali treatment on tensile properties of curaua fiber green composites

Abstract: This paper describes development and improvement of mechanical properties of a so-called green composite that was fabricated by reinforcing a cornstarch-based biodegradable resin with high-strength natural fibers extracted from a plant named curaua. Two fabrication methods are proposed, in which stretched slivers of curaua fibers are prepared as reinforcement to increase the composite strength. Moreover, highly concentrated alkali treatment was applied to curaua fibers to improve mechanical properties of green composites. Tensile test results showed that alkali-treated fiber composites increased in fracture strain twice to three times more than untreated fiber composites, without a considerable decrease in strength. This result proves that appropriate alkali treatment is a key technology for improving mechanical properties of cellulose-based fiber composites.

Pre-treatment of flax fibers for use in rotationally molded biocomposites

Abstract: The objective of this study was to determine the effects of pre-treated flax fibers on the performance of the fiber-reinforced composites. Lack of good interfacial adhesion and poor resistance to moisture absorption make the use of natural fiber-reinforced composites less attractive. In order to improve fiber/matrix interfacial properties, fibers were subjected to chemical treatments, namely, mercerization, silane treatment, benzoylation, and peroxide treatment. Selective removal of non-cellulosic compounds constitutes the main objective of the chemical treatments of flax fibers to improve the performance of fiber-reinforced composites. Flax fibers were derived from Saskatchewan-grown flax straws. Composites consisting of high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE) or HDPE/LLDPE mix, chemically treated fibers and additives were prepared by the extrusion process. The test samples were prepared by rotational molding. The fiber surface morphology and the tensile fracture surfa...

Engineering nanoscale order into a designed protein fiber

Abstract: We have established a designed system comprising two peptides that coassemble to form long, thickened protein fibers in water. This system can be rationally engineered to alter fiber assembly, stability, and morphology. Here, we show that rational mutations to our original peptide designs lead to structures with a remarkable level of order on the nanoscale that mimics certain natural fibrous assemblies. In the engineered system, the peptides assemble into two-stranded α-helical coiled-coil rods, which pack in axial register in a 3D hexagonal lattice of size 1.824 nm, and with a periodicity of 4.2 nm along the fiber axis. This model is supported by both electron microscopy and x-ray diffraction. Specifically, the fibers display surface striations separated by nanoscale distances that precisely match the 4.2-nm length expected for peptides configured as α-helices as designed. These patterns extend unbroken across the widths (≥50 nm) and lengths (>10 μm) of the fibers. Furthermore, the spacing of the striations can be altered predictably by changing the length of the peptides. These features reflect a high level of internal order within the fibers introduced by the peptide-design process. To our knowledge, this exceptional order, and its persistence along and across the fibers, is unique in a biomimetic system. This work represents a step toward rational bottom-up assembly of nanostructured fibrous biomaterials for potential applications in synthetic biology and nanobiotechnology.