Showing papers on "Fiber published in 1983"

High-density absorbent structures

Abstract: Absorbent structures comprising a mixture of hydrophilic fibers and discrete particles of a water insoluble hydrogel are disclosed. The fiber/hydrogel ratios range from about 30:70 to about 98:2. The absorbent structures have a density of from about 0.15 g/cm 3 to about 1 g/cm 3 . The structures are flexible, and have superior absorption capacities for water and body fluids.

Adhesion of Graphite Fibers to Epoxy Matrices: I. The Role of Fiber Surface Treatment

Abstract: Adhesion between graphite fibers and epoxy matrices is a necessary and sometimes controlling factor in achieving optimum performance. Manufacturers′ proprietary fiber surface treatments promote adhesion without providing a basic understanding of the fiber surface properties altered through their use. This study has combined fiber surface chemistry, morphology, interfacial strength measurements and fracture characterization in order to elucidate the role of surface treatments. The results of this investigation lead to the conclusion that surface treatments designed to promote adhesion to epoxy matrix materials operate through a two-part mechanism. First, the treatments remove a weak outer fiber layer initially present on the fiber. Second surface chemical groups are added which increase the interaction with the matrix. Increases in fiber surface area are not an important factor in promoting fiber-matrix adhesion. In some cases the upper limit to fiber-matrix interfacial shear strength is the intri...

Adhesion of Graphite Fibers to Epoxy Matrices: II. The Effect of Fiber Finish

Abstract: Reinforcing fibers are available from various manufacturers with matrix compatible “finishes” applied to them. Usually these finishes or coatings are 100–200 nm thick resin layers applied after surface treatment. Their function has been hypothesized as being to enhance adhesion through either protecting the fiber from handling damage, protecting the fiber surface reactivity, or improving fiber wettability. This study of finished and unfinished graphite fibers concludes that the mechanism by which an epoxy compatible finish operates is different from what has been hypothesized to date. The finish layer creates a brittle interphase layer between the fiber and matrix which increases the interfacial shear strength but at the expense of changing the failure mode from interfacial to matrix.

Particle-packed fiber article having antibacterial property

Abstract: Specific zeolite particles retaining therein a metal ion having a bactericidal activity are packed and retained in a mixed fiber assembly composed of low-melting thermoplastic synthetic fibers and ordinary fibers. The zeolite particles are retained by welding of the low-temperature thermoplastic synthetic fibers but in a state of allowing the contact thereof with an external fluid. The particle-packed fiber article has an excellent and durable antibacterial activity and can be used in various fields.

Vanadium pentoxide gels

Abstract: Vanadium pentoxide gels consist of entangled polymeric fibers. Electron diffraction experiments have shown that these fibers are actually arranged as flat ribbons about 103 A long, 102 A wide, and 10 A thick. A two-dimensional order is observed along these ribbons which does not vary upon swelling. The two-dimensional cell parameters a = 27.0 A and b = 3.6A suggest that the organization within the fibers is closely related to the lamellar structure of orthorhombic V2O5. The fiber is made of basic blocks containing 10 vanadium atoms along the a direction. These blocks seem to be linked together by water molecules which are strongly bonded to the structure and cannot be removed without crystallization of the xerogel into orthorhombic V2O5.

Optical fiber delay line signal processing

Abstract: Single-mode optical fiber is an attractive delay medium for processing microwave frequency signals due to its extremely low loss (<0.1 dB/µs) and large available time-bandwidth product (in excess of 10/sup 5/). Recent progress in the efficient tapping of light from single-mode fibers has made it possible to construct recirculating and nonrecirculating (tapped) delay-line structures that can perform a variety of important signal processing functions. These functions include coded sequence generation, convolution, correlation, matrix-vector multiplication, and frequency filtering. This paper presents the fundamental properties of single-mode fiber delay lines and reviews recent experimental results that demonstrate the feasibility of fiber delay-line devices for broad-band signal-processing applications.

The Influence of Dietary Fiber Source on Human Intestinal Transit and Stool Output

Abstract: Wheat bran ground to a coarse and fine particle size, purified cellulose and ethanol-extracted cabbage fiber, fed to 24 adult males during an 80-day metabolic trial, were examined for effects on intestinal transit time, laxation and stool composition. Brilliant blue, plastic pellets, polyethylene glycol (PEG)-4000 and Cr(III) mordanted onto isolated bran fiber were simultaneously administered for transit measurements. Intersubject variability in response to fiber source was highly significant for all transit and stool measurements. Only coarse bran or cellulose addition increased transit speed (decreased transit time) over basal rates. Grinding of bran significantly reduced fecal output because of reduced fecal water. Only subjects consuming cellulose or fine bran reported difficult or uncomfortable defecations. Though cabbage produced the smallest fecal output, stools had a high moisture content comparable to those obtained from coarse bran, which suggests a large microbial output in response to a fermentable substrate. Significant negative correlations were produced when changes in dry matter or cell wall intakes were regressed with Cr (III) transit. These findings suggest that the level of either food or fiber in the diet are variables that influence intestinal transit time and should be controlled in studies measuring it. Increases in fiber intake linearly increased fecal output of water and dry matter. Regression slopes were characteristic of each fiber source.

The relationship between the physical structure and the microscopic deformation and failure processes of poly(p-phenylene terephthalamide) fibers

Abstract: Relations between the physical structure and the deformation and failure processes of poly(p-phenylene terephthalamide) (PPTA) fibers are reported. The effects of the physical processes involved in fiber fabrication, including the crystallization of PPTA-H2SO4 dopes under stress, are considered in relation to their effect on the structure of the fiber. The deformation and failure processes together with the structure of the fiber are discussed in the light of fracture-topography studies of fiber-epoxy composite strands, single filaments, HCl-etched and unetched yarns, and transmission optical microscopy studies of stressed and unstressed yarns. In view of these observations, the physical structure of PPTA fibers is discussed in terms of pleated H-bond sheets, the macromolecular chain-end concentration and distribution, and the presence of impurities. The structural parameters that affect the failure processes of these fibers and how such parameters can be modified by service environment conditions are also addressed.

Evaluation of surface treatments for fibers in composite materials

Abstract: An embedded single filament test has been developed that measures the cumulative distribution of critical fibers lengths for a given fiber-polymer system. The mean value of critical lengths and the dispersion of values are a function of both the shear transmission characteristics of the interface and the strength characteristics of the fibers. A computer model of the stochastic fracture process has been developed that incorporates a mixed-element, weakest-link model to describe the strength properties of the fibers, a random generator to describe the stochastics of multiple fiber fracture, and a shear-lag analysis to describe the shear transmission across the interface. From the measurement of critical fiber lengths, a value for the magnitude of the shear transmission across the fiber-polymer interface, τ, can be determined. From measured values fiber strength, the ability of a surface treatment to protect a given fiber can be determined. A variety of surface treatments for E-glass are evaluated in a number of thermoplastic polymer materials. The experimental technique and the associated analysis are shown to be valuable in separating the coupling and sizing effects of the fiber surface treatment formulations. This should be of particular value in the optimization of commercial fiber treatment formulations.

Ultrafine fiber entangled sheet and method of producing the same

Abstract: An entangled non-woven fabric having a fiber structure which comprises a portion (A) in which ultrafine fiber bundles consisting of ultrafine fibers of a size of not greater than about 0.5 denier are entangled with one another and a portion (B) in which ultrafine fibers to fine bundles of ultrafine fibers branch from the ultrafine fiber bundles and are entangled with one another, and in which portions (A) and (B) are nonuniformly distributed in the direction of fabric thickness. The product of this invention has high flexibility as well as good shape retention. The invention also relates to a grained sheet having on at least one of its surfaces a grain formed by a fiber structure composed of ultrafine fibers to fine bundles of ultrafine fibers and having a distance between the fiber entangling points of not greater than about 200 microns, and a resin in the gap portions of the fiber structure. The grained sheet of the invention has high flexibility resistance, shearing fatigue resistance and scratch and scuff resistance.

Solution processing and properties of molecular composite fibers and films

Abstract: Experimental studies of fiber wet-spinning and solution processing of films of molecular composites are presented. The rigid rod polymer was poly (p-phenylenebenzobisthiazole) (PPBT) and the flexible polymers were poly (2,5(6′)-benzimidazole) (ABPBI) and poly (2,5(6′)-benzothiazole) (ABPBT). Effects of the flexible polymer molecular entanglements in solution on the processing are discussed. These fibers and films have very high modulus and strength, which improve upon heat treatment. The uniaxial modulus of highly oriented molecular composites follows the linear rule of mixtures.

Numerical Prediction of Fiber Orientation in Dilute Suspensions

Abstract: A numerical scheme for the determination of the fiber orientation state in dilute suspensions is developed. Fiber orientations are calculated from the numerical integration of Jeffery's orienta tion equation along the streamlines obtained on the basis of the finite element method. Numerical solutions of the fiber orientation state are presented for the simple shear flow, the fountain flow and the flow in an infinite expansion.

Thermal wave remote and nondestructive inspection of polymers

Abstract: Optically generated thermal waves propagating in various kinds of polymers (adhesives, coatings, fiber reinforced polybutyleneterephthalate, oriented polyethylene) are analyzed by photothermal detection. Some results from this remote technique are difficult to obtain by conventional methods.

Synergistic effect of metal flake and metal or metal coated fiber on emi shielding effectiveness of thermoplastics

Abstract: Conductive thermoplastic having high EMI shielding effectiveness comprise a thermoplastic condensation polymer and incorporated therein a synergistic combination of metal flake and conductive metal or metal coated fiber.

On the morphology of aromatic polyamide fibers (Kevlar, Kevlar-49, and PRD-49)

Abstract: Three types of aromatic polyamide fibers (Kevlar, Kevlar-49, and PRD-49) were studied by transmission electron microscopy, secondary electron imaging, and electron diffraction techniques. Ultramicrotomy, ion-thinning, and brittle fracture techniques were used to prepare specimens which revealed both longitudinal and transverse fiber structures. Aromatic polyamide fibers exhibit both a “skin” and a “core” structure. The core morphology is shown to be consistent with a layered structure where individual layers are stacked perpendicular to the fiber axis and are composed of rodlike crystallites whose c axes are parallel to the fiber axis. Electron diffraction results indicate that hydrogen bonds are located nearly in the radial direction of the fiber. The crystallite layer thickness appears to depend upon the most probable molecular weight of the fiber. Longer crystallites which pass through two or more layers are present, and may control the strength of the fiber in the axial direction.

Clarification of pear juice by hollow fiber ultrafiltration

Abstract: Hollow fiber ultrafiltration was successfully applied to obtain a clear, amber-colored pear juice For the three hollow fiber membrane cartridges tested (50,000, 30,000, and 10,000 dalton molecular weight cut-off), the process parameters were optimized and found to be similar The permeate flux increased with increased transmembrane pressure and then declined Flux reached a maximum at an average transmembrane pressure of 157 kPa with an average feed stream velocity of 015 meters/set at 50°C Higher flux was obtained at higher temperatures within the temperature limitations of the membrane Flux decreased linearly with the logarithm of the concentration

High strength and modulus polyvinyl alcohol fibers and method of their preparation

Abstract: Polyvinyl alcohol of molecular weight over 500,000 (i.e. 1,500,000 to 2,500,000) is spun as a dilute solution (2-15%) in a relatively non-volatile solvent such as glycerin. The resultant gel fiber is extracted with a volatile solvent such as methanol and dried. Upon stretching at one or more stages during the process, fibers of tenacity above 10 g/denier and modulus above 200 g/denier (e.g. 18 and 450, respectively) are produced.

How modal noise in multimode fibers depends on source spectrum and fiber dispersion

Abstract: The speckle contrast for multimode fibers, and thus the modal noise, is essentially given by the impulse response of the fiber and the power spectrum of the source. Theoretical and experimental results show that laser sources with a large spectrum of narrow longitudinal modes may cause high speckle contrast and important modal noise over more than 1-km length in graded-index multimode fibers.

Composite containing polyolefin fiber and polyolefin polymer matrix

Abstract: A composite containing a network of ultrahigh molecular weight polyethylene or polypropylene fibers of high tenacity and modulus and a matrix which has ethylene or propylene crystallinity, e.g. polyethylene, polypropylene or copolymers. The composite can be formed by heating the matrix to its melting or sticking temperature around the fibers. The composite retains a high proportion of the tenacity of the fiber.

Regulation of synaptic position, size, and strength in anuran skeletal muscle

Abstract: An analysis of the physiology, morphology, and position of endplates on identified fibers in the Xenopus laevis pectoralis muscle has revealed the following. 1. The percentage of fibers with one endplate is lower in large muscles, and within the same muscle, singly innervated fibers are smaller than dually innervated fibers. 2. Single junctions tend to be stronger than junctions on dually innervated fibers. 3. Single junctions typically are located near the middle of their fibers, while the endplates on dually innervated fibers are located toward either end and usually are separated by at least 20% of the total fiber length. A significant proportion of dually innervated fibers appears to be innervated by the same axon at both junctions. 4. Junctions on the same dually innervated fiber tend to be more similar in length than do junctions on different fibers of the same input resistance. This observation is the same whether both junctions on a given fiber are formed by the same or different axons. There is no corresponding tendency for greater similarity in physiological strength of paired junctions, which frequently show large differences in endplate potential amplitude. 5. The total terminal length on dually innervated fibers of equivalent input resistance is inversely correlated with the mean release per unit length and total release of both junctions. There is no apparent correlation between the distance separating endplates and their strength or length. The data support a model of synaptic regulation in which nerve terminals are attracted, grow, and are maintained in proportion to the amount of a substance supplied by muscle fibers. Our findings suggest that such a substance is produced or distributed uniformly throughout each fiber in amounts proportional to the fiber size and inversely proportional to the total transmitter output of all junctions innervating the fiber. A form of competitive interaction between the terminals which helps to determine synaptic spacing may involve local depletion or inactivation of this substance.

Coated extended chain polyolefin fiber

Abstract: High tenacity, high modulus ultrahigh molecular weight fibers of polyethylene or polypropylene are coated with polyethylene, polypropylene or an ethylene and/or propylene copolymer. The coating improves certain properties of the monofilament or multifilament, including adhesion to various matrices in complex composites and resistance of the fiber to fibrillation.

Instabilities of a Finitely Deformed Fiber-Reinforced Elastic Material

Abstract: The instabilities of a finitely deformed Blatz-Ko material reinforced with fibers in a single direction (an anisotropic, nonlinearly elastic material) are examined. The loading is one of plane strain uniaxial stress with the load axis being inclined with respect to the fiber direction. In general one finds a critical applied stress (or stretch) at which surface instabilities of the body occur. This is then followed by a shear band-type instability. For a certain range of fiber orientations these instabilites appear a maximum stress level has been reached. It has also been found that when the fiber direction approaches the loading axis, the material is stabilized in tension but destabilized in compression.

Plant Fiber and Blood Pressure

Abstract: Vegetarians and other persons with high fiber intakes have lower average blood pressures than persons with low fiber intakes. We assessed blood pressures in 12 nonobese, insulin-treated, d...

Necking and drawing in polymeric fibers under tension

Abstract: A constitutive relation is proposed for the dependence of the tension in a thin polymeric fiber on the variation of the stretch ratio λ along the fiber axis. When this relation is placed in the equation of balance of forces, it yields a nonlinear second-order differential equation for λ whose equilibrium solutions (for a long fiber) are known in other contexts. The solutions describe necks, bulges, drawing configurations, and periodic striations. The assumption that motions resulting from gradual changes in tension or length are homotopies formed from these equilibrium solutions is compatible with many of the observed properties of tension-induced necking and drawing in fibers of such polymers as nylon and polyethylene.

A fiber optic PCO2 sensor

Abstract: The theory, construction and performance of a catheter tip optical PCO2 probe is described. The sensor, called the Opticap, is made with plastic fiber optics. One fiber carries light to the sensitive tip which is a silicone rubber tube 0.6 mm dia. X 1.0 mm long filled with a phenol red-KHCO3 solution. Ambient PCO2 controls the pH of the solution which influences the optical transmittance of the phenol red. A second fiber carries the transmitted signal to a receiver; the resulting electrical signal is linearly related to the PCO2 over the range of 2.7 to 10.7 kPa. The probe was tested as a tissue PCO2 sensor on the cerebral cortex of the cat and as an arterial PCO2 sensor. Drift over one day's use was 0.6 KPa or less and individual probes have been used as long as 12 weeks.

Method and apparatus for producing blends of resinous, thermoplastic fiber, and laminated structures produced therefrom

Abstract: Reinforced structures of graphite, fiberglass, and the like, together with thermoplastic resinous fibers such as in ribbon, filament and monofilament form are produced. The graphite fiber is combined or blended with a resinous fiber to form a single yarn. The blended yarn is then woven into a soft, supple and flexible fabric having the appropriate concentration of graphite and resin, and with good uniform characteristics. Hybrid fabrics produced by interweaving graphite and the polymeric fibers, ribbon, etc., may be utilized instead of the blended yarn. The fabric is finally shaped to conform with a mold or substrate and heated to melt the resin and produce the resin-graphite laminate.