Showing papers on "Fiber published in 2003"

Photonic crystal fibers

Abstract: Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length Largely through their ability to overcome the limitations of conventional fiber optics—for example, by permitting low-loss guidance of light in a hollow core—these fibers are proving to have a multitude of important technological and scientific applications spanning many disciplines The result has been a renaissance of interest in optical fibers and their uses

Controlling the dissolution of dissolvable polymer components in plural component fibers

Abstract: The dissolution of dissolvable components in plural component polymer fibers is achieved by providing a polymer fiber including at least two sections, where at least one fiber section includes a dissolvable component. The rate at which at least part of the fiber dissolves is controlled by at least one of a fiber section having a non-round cross-sectional geometry, and at least two fiber sections including two different dissolvable components. In an exemplary embodiment, island-in-the-sea fibers are formed with non-round and elongated cross-sectional geometries. In another embodiment, sheath-core fibers are formed in which the sheath and core include different dissolvable components.

Effects of wood fiber characteristics on mechanical properties of wood/polypropylene composites

Abstract: Commercial wood flour, the most common wood-derived filler for thermoplastics, is produced in a mixture of particle sizes and generally has a lower aspect ratio than wood and other natural fibers. To understand how wood flour and fiber characteristics influence the mechanical properties of polypropylene composites, we first investigated the effect of different sizes of wood flour particles on the mechanical properties of wood-flour-filled polypropylene composites. We then compared the properties of wood-flour-filled composites to those of composites reinforced with refined wood fiber. We also studied the effect of a maleated polypropylene coupling agent on composite properties. Wood flour particles (35, 70, 120, and 235 mesh) were compounded at 40% by weight with polypropylene. Increases in tensile and flexural strength and modulus of the wood flour composites were found to correspond with increases in aspect ratio. Notched impact energy increased with increasing particle size, whereas unnotched impact energy decreased with increasing particle size. Refined wood fiber and 40-mesh wood flour was compounded at 20% and 40% by weight with polypropylene. Wood fiber resulted in higher strengths at both filler levels and higher moduli at the 40% level compared to the strength properties of wood flour composites. The higher aspect ratio of the wood fiber had little effect on impact energy. The maleated polypropylene coupling agent caused greater strength increases in wood fiber composites than in wood flour composites. The coupling agent did not significantly affect tensile or flexural moduli. Our results clearly support the use of higher aspect ratio wood fibers and coupling agents for increasing the strength of wood/plastic composites.

Incorporation of experimentally-derived fiber orientation into a structural constitutive model for planar collagenous tissues

Abstract: Structural constitutive models integrate information on tissue composition and structure, avoiding ambiguities in material characterization. However, critical structural information (such as fiber orientation) must be modeled using assumed statistical distributions, with the distribution parameters estimated from fits to the mechanical test data. Thus, full realization of structural approaches continues to be limited without direct quantitative structural information for direct implementation or to validate model predictions. In the present study, fiber orientation information obtained using small angle light scattering (SALS) was directly incorporated into a structural constitutive model based on work by Lanir (J. Biomech., v. 16, pp. 1-12, 1983). Demonstration of the model was performed using existing biaxial mechanical and fiber orientation data for native bovine pericardium (Sacks and Chuong, ABME, v.26, pp. 892-902, 1998). The structural constitutive model accurately predicted the complete measured biaxial mechanical response. An important aspect of this approach is that only a single equibiaxial test to determine the effective fiber stress-strain response and the SALS-derived fiber orientation distribution were required to determine the complete planar biaxial mechanical response. Changes in collagen fiber crimp under equibiaxial strain suggest that, at the meso-scale, fiber deformations follow the global tissue strains. This result supports the assumption of affine strain to estimate the fiber strains. However, future evaluations will have to be performed for tissue subjected to a wider range of strain to more fully validate the current approach.

Electrospinning and Stabilization of Fully Hydrolyzed Poly(Vinyl Alcohol) Fibers

Abstract: Fully (99+ %) hydrolyzed poly(vinyl alcohol) (PVA) was electrospun from water using Triton X-100 surfactant to lower the surface tension. The diameter of the electrospun PVA fibers ranged from 100 to 700 nm. Treatment of the PVA fiber mats with methanol for 8 h stabilized the fibers against disintegration in contact with water. In addition, the mats showed increased mechanical strength due to increased crystallinity following post-spinning treatment with methanol. We suggest that methanol treatment serves to increase the degree of crystallinity, and hence the number of physical cross-links in the electrospun PVA fibers. This may occur by removal of residual water within the fibers by the alcohol, allowing PVA−water hydrogen bonding to be replaced by intermolecular polymer hydrogen bonding resulting in additional crystallization. Potential applications of electrospun PVA include filters, precursors to graphitic fibers, and biomedical materials.

On the mechanism of adhesion in biological systems

Abstract: I study adhesion relevant to biological systems, e.g., flies, crickets and lizards, where the adhesive microstructures consist of arrays of thin fibers. The effective elastic modulus of the fiber arrays can be very small which is of fundamental importance for adhesion on smooth and rough substrates. I study how the adhesion depend on the substrate roughness amplitude and apply the theoretical results to lizards.

Oil Removal from Water by Selective Sorption on Hydrophobic Cotton Fibers. 1. Study of Sorption Properties and Comparison with Other Cotton Fiber-Based Sorbents

Abstract: Hydrophobic cotton fibers, obtained by acylation of cellulose with fatty acid using microwaves radiations, have a high selective affinity for vegetable or mineral oil, fuel, and petroleum, in aqueous medium. Their sorption capacity (SC) (weight of liquid picked up by a given weight of sorbent) is about 20 g/g, after draining. They are reusable after simple squeezing, and their SC reaches a constant value, ca. 12 g/g. Moreover, this product is stable in water, whereas raw cotton can develop molds, after oil sorption. Besides, it is also biodegradable.

Engineered Steel Fibers with Optimal Properties for Reinforcement of Cement Composites

Abstract: Although steel fibers have been used in cement and concrete composites for more than four decades, most of the steel fibers on the market today have been introduced prior to 1980. This is in sharp contract to the continuous progress and development in the cement matrix itself. Following a brief summary of the main properties and limitations of steel fibers used in cement based composites, this paper describes the rationale and technical background behind the development and design of a new generation of steel fibers for use in cement, ceramic and polymeric matrices. These fibers are engineered to achieve optimal properties in terms of shape, size, and mechanical properties, as well as compatibility with a given matrix. They are identified as Torex fibers. Typical tests results are provided and illustrate without any doubt the superior performance (2 to 3 times) of Torex fibers in comparison to other steel fibers on the market. The new fibers will advance the broader use of high performance fiber reinforced cement composites in structural applications such as in blast and seismic resistant structures, as well as in stand-alone applications such as in thin cement sheet products.

Carbon storage potential in natural fiber composites

Abstract: The environmental performance of hemp based natural fiber mat thermoplastic (NMT) has been evaluated in this study by quantifying carbon storage potential and CO2 emissions and comparing the results with commercially available glass fiber composites. Non-woven mats of hemp fiber and polypropylene matrix were used to make NMT samples by film-stacking method without using any binder aid. The results showed that hemp based NMT have compatible or even better strength properties as compared to conventional flax based thermoplastics. A value of 63 MPa for flexural strength is achieved at 64% fiber content by weight. Similarly, impact energy values (84–154 J/m) are also promising. The carbon sequestration and storage by hemp crop through photosynthesis is estimated by quantifying dry biomass of fibers based on one metric ton of NMT. A value of 325 kg carbon per metric ton of hemp based composite is estimated which can be stored by the product during its useful life. An extra 22% carbon storage can be achieved by increasing the compression ratio by 13% while maintaining same flexural strength. Further, net carbon sequestration by industrial hemp crop is estimated as 0.67 ton/h/year, which is compatible to all USA urban trees and very close to naturally, regenerated forests. A comparative life cycle analysis focused on non-renewable energy consumption of natural and glass fiber composites shows that a net saving of 50 000 MJ (∼3 ton CO2 emissions) per ton of thermoplastic can be achieved by replacing 30% glass fiber reinforcement with 65% hemp fiber. It is further estimated that 3.07 million ton CO2 emissions (4.3% of total USA industrial emissions) and 1.19 million m3 crude oil (1.0% of total Canadian oil consumption) can be saved by substituting 50% fiber glass plastics with natural fiber composites in North American auto applications. However, to compete with glass fiber effectively, further research is needed to improve natural fiber processing, interfacial bonding and control moisture sensitivity in longer run.

Design and modeling of a photonic crystal fiber gas sensor

Abstract: We report the modeling results of an all-fiber gas detector that uses photonic crystal fiber (PCF). The relative sensitivity of the PCF as a function of the fiber parameters is calculated. Gas-diffusion dynamics that affect the sensor response time is investigated theoretically and experimentally. A practical PCF sensor aiming for high sensitivity gas detection is proposed.

Crack growth resistance of hybrid fiber reinforced cement composites

Abstract: Crack propagation in cement-based matrices carrying hybrid fiber reinforcement was studied using contoured double cantilever beam (CDCB) specimens. Influence of fiber type and combination was quantified using crack growth resistance curves. It was demonstrated that a hybrid combination of steel and polypropylene fibers enhances the resistance to both nucleation and growth of cracks, and that such fundamental fracture tests are very useful in developing high performance hybrid fiber composites. The influence of number of variables which would otherwise have remained obscured in normal tests for engineering properties become apparent in the fracture tests. The paper emphasizes the desired durability characteristics of these composites and discusses their current and future applications.

Systems and methods for spectroscopy of biological tissue

Abstract: The system and method of the present invention relates to using spectroscopy, for example, Raman spectroscopic methods for diagnosis of tissue conditions such as vascular disease or cancer. In accordance with a preferred embodiment of the present invention, a system for measuring tissue includes a fiber optic probe having a proximal end, a distal end, and a diameter of 2 mm or less. This small diameter allows the system to be used for the diagnosis of coronary artery disease or other small lumens or soft tissue with minimal trauma. A delivery optical fiber is included in the probe coupled at the proximal end to a light source. A filter for the delivery fibers is included at the distal end. The system includes a collection optical fiber (or fibers) in the probe that collects Raman scattered radiation from tissue, the collection optical fiber is coupled at the proximal end to a detector. A second filter is disposed at the distal end of the collection fibers. An optical lens system is disposed at the distal end of the probe including a delivery waveguide coupled to the delivery fiber, a collection waveguide coupled to the collection fiber and a lens.

Effect of Storage Conditions on Quality Characteristics of Bologna Sausages Made with Citrus Fiber

Abstract: Bologna sausage with added citrus fiber was improved nutritionally in fiber content and had decreased residual nitrite levels and a delay in the oxidation process as determined by TBA values and red color Only TBA values and redness were influenced by storage conditions (light and darkness) mainly due to the oxidant effect attributable to light In both cases these effects were minimized by the citrus fiber Citrus fiber at all concentrations made the products harder and less springy and chewy All samples had similar satisfactory quality scores except bologna with 2% citrus fiber, which had the lowest scores Microbial growth was not modified by citrus fiber during storage

Nematic Elastomer Fiber Actuator

Abstract: We report the synthesis and physical studies of a liquid crystalline elastomer fiber consisting of two side-chain liquid crystalline acrylates and a nonmesogennic comonomer side group that acts as a reactive site for cross-linking. The terpolymer was synthesized by radical polymerization, and the cross-linking of the network was achieved by using a diisocyanate unit. The fiber formed shows good liquid crystal alignment texture under a cross-polarizer microscope. Thermoelastic response shows strain changes through the nematic−isotropic phase transition of about 30−35%. A retractive force of nearly 300 kPa was measured in the isotropic phase. Static work loop studies show the viscoelastic losses in these materials to be very small. We also present preliminary studies on the effect of doping carbon nanotubes on the induced strain at the nematic−isotropic transition.

Biocomposites Made from Short Abaca Fiber and Biodegradable Polyesters

Abstract: Natural fiber-reinforced biodegradable polyester composites were prepared from biodegradable polyesters and surface-untreated or -treated abaca fibers (length ca. 5 mm) by melt mixing and subsequent injection molding. Poly(butylene succinate)(PBS), polyestercarbonate (PEC)/poly(lactic acid)(PLA) blend, and PLA were used as biodegradable polyesters. Esterifications using acetic anhydride and butyric anhydride, alkali treatment, and cyanoethylation were performed as surface treatments on the fiber. The flexural moduli of all the fiber-reinforced composites increased with fiber content. The effect of the surface treatment on the flexural modulus of the fiber-reinforced composites was not so pronounced. The flexural strength of PBS composites increased with fiber content, and esterification of the fiber by butyric anhydride gave the best result. For the PEC/PLA composites, flexural strength increased slightly with increased fiber content (0-20 wt.-%) in the case of using untreated fiber, while it increased considerably in the case of using the fiber esterified by butyric anhydride. For the PLA composite, flexural strength did not increase with the fiber reinforcement. The result of soil-burial tests showed that the composites using untreated fiber have a higher weight loss than both the neat resin and the composites made using acetylated fiber.

PDMS 2D optical lens integrated with microfluidic channels: principle and characterization.

Abstract: In this paper, the fabrication and characterization of PDMS 2D-optical lenses are reported. These lenses are designed in order to improve the performance of fluorescent spectroscopy detection performed on a portable chip using optical fibers. The fabrication process of the PDMS layer is first detailed, and the patterns are then checked with a SEM. By comparing various interfacial structures, it is shown that the beam properties of the light coming out from the fiber can be modified depending on the lens curvature radius. As a consequence, for a constant dye concentration, the use of such lenses can increase the intensity of fluorescent response close to the fiber or far from the fiber, compared to the same design with a flat interface. This excitation improvement corresponding to a stronger response from the dye then consequently leads to around three times higher sensitivity of the on-chip detection method for fluorescent spectroscopy.

Preparation of high dietary fiber powder from lemon juice by-products

Abstract: Lemon ( Citrus limon cv Fino) juice industry by-products were used to obtain high dietary fiber powder. The effect of processing variables (direct drying, and washing previous to drying) on functional properties, fiber content and type, microbial quality and physicochemical properties of the fiber were evaluated. The obtained fiber powder had good functional, microbial quality and favorable physicochemical characteristics to be used in food formulations. Processing conditions affected fiber composition and properties. Water holding capacity was enhanced by washing (7 g water/g non-washed fiber powder; 12.6 g water/g washed fiber powder) and slightly decreased by the reduction in fiber particle size. Oil holding capacity (6.7 g oil/g fiber powder) was not affected by those factors. Acid detergent and neutral detergent fibers were highest in powder from washed lemon residue (23.73 and 32.91%, respectively). a w was lowest in washed lemon fiber powder (0.13). Washing prevented fiber browning during drying as reflected in color parameters. Washing water rinsed green components. Drying was the responsible for the decrease of bacterial populations (approx. 90% reduction in microbial counts).