Dyne fibers


Preforms manufactured by MCVD, PCVD, OVD, and VAD all must be drawn into fiber in a similar manner. Standard fibers are drawn to 125 ]Am in diameter from preforms on the order of 2 to 7.5 cm diameter. Fibers are drawn by hoi ding the preform vertically and lowering it into a furnace. The preform is heated to a temperature at which the glass softens (2200°C) until a gob of glass stretches from the tip of the preform and drops under the force of gravity. A neck-down region is formed at this point, providing the transition between preform and fiber. Fiber is drawn by means of a capstan system, and its diameter is controlled by a diameter monitor that adjusts the draw speed at a fixed furnace temperature. The result is long lengths of uniform fiber.  [c.257]

Visual and Manual Tests. Synthetic fibers are generally mixed with other fibers to achieve a balance of properties. Acryhc staple may be blended with wool, cotton, polyester, rayon, and other synthetic fibers. Therefore, as a preliminary step, the yam or fabric must be separated into its constituent fibers. This immediately estabUshes whether the fiber is a continuous filament or staple product. Staple length, brightness, and breaking strength wet and dry are all usehil tests that can be done in a cursory examination. A more critical identification can be made by a set of simple manual procedures based on burning, staining, solubiUty, density deterrnination, and microscopical examination.  [c.276]

High Strength Fibers by Conventional Solution Spinning. As a reinforcing material for ambient-cured cement building products, acrylics offer three key properties high elastic modulus, good adhesion, and good alkali resistance (73). The high modulus requires an unusually high stretch orientation. This can be accompHshed by stretching the fiber above its glass-transition temperature, T. Normally this is done in boiling water or steam to  [c.285]

Nonwoven Geotextiles. There are two basic manufacturing processes by which a nonwoven geotextile is produced a one-stage or continuous process where the fibers are spun and bonded in one continuous process, and a two-stage process where fibers are laid down and then bonded (see NONWOVEN fabrics). The most common types of bonding processes are the spun-bonded process, melt- or heat-bonded, resin-bonded, and needle-punched (Fig. 2). Each of the processes results in a geotextile that may have vastiy different characteristics than one formed otherwise. Depending on the end use of the material, this may affect the choice of the geotextile to be used on a specific project.  [c.257]

Continuous Dra.wing Process. Textile glass filaments are made by a process different from that used for making discontinuous fibers, but hteraHy parallel to a standard organic polymer melt spinning operation that does not employ a screw extmder. Premelted glass or glass marbles are fed iato an electrically heated furnace called a bushing which contains 204 platinum nozzles (or multiples thereof). The exiting glass filaments are drawn down iato the desired diameters, water sprayed, coated with a sizing, and the multiple filaments are collected as bundles of strands which are then wound onto a suitable cone.  [c.69]

These fibers are collected and coated with a protective spray containing either lubricants, binders, or antistatic and wetting agents. Other versions of the rotary process are (/) the wheel centrifugal process where molten glass is cascaded over spinning wheels and the formed fibers are stretched and broken by variations ia the wheel speeds prior to being collected, and (2) the Downey process where molten glass is dropped onto a centrifuge wheel and then exits into a stream of high velocity air much like the melt blown process for making textile nonwovens.  [c.69]

Manufacturing. The use of advanced textile materials ia manufacturing is a diverse and expanding market. Optical fibers are being increasingly used in telecommunications, computers, cable television, and to faciHtate process control in the nuclear, petrochemical and chemical, and food industries. Although most optical fibers are glass or of related inorganic composition, there are optical fibers for special appHcations comprised of poly(methyl methacrylate), polystyrene, and polycarbonate that are coextmded with fluorinated acrylate polymers. Polyacetal, ie, poly(oxymethylene) fiber has also been used as a reinforcing material for optical fibers. Basic fiber properties required for an optical fiber are (/) a stmcture with a high refractive index core and a low refractive index cladding (sheath bonded to core under high temperature and pressure) (2) fiber with a low attenuation or low power loss of light over distance and (J) fiber with low dispersion or pulse broadening as light travels down the fiber (36).  [c.72]

Most architectural fabrics are usually flexible composites comprised of glass fibers coated with fluorocarbons to resist wind, mechanical forces, and outdoor environmental degradation. The airport terminal in Saudi Arabia, and the roofs for the Hubert Humphrey Dome in Minneapolis and the Tokyo Dome Stadium are a few examples of the successful use of architectural fabrics.  [c.72]

Many parameters are involved in the dry-jet wet technique, and these interact during the extmsion/coagulation steps. The principal variables are more or less the same for all spinning techniques and include dope composition, dope viscosity, spinning temperature, dope-pumping rate, composition of coagulants (interior and exterior), spinneret distance from the coagulation bath, interior-medium flow rate, coagulation temperature, and fiber draw rate (take-up rate). For example, the relationships among fiber dimensions, fiber morphology, fiber properties, and spinning variables are given in the Hterature for polysulfone hoUow fibers spun from a dope composition of polysulfone/poly(vinylpyrroHdinone) (PVP) in dimethyl acetamide (DMA) (3,7,15). The composition of the bore fluid and the rate of its deUvery are important parameters for the initia tion of fiber formation. The dope emerging from the orifice immediately interacts with the interior medium (which can be either gas or Hquid), and the pressure within the nascent bore determines the initial filament diameter. For some dope compositions, the bore fluid contains dry nitrogen or mineral oil, whose only function is to maintain the aimular configuration of the fiber as it is drawn down and coagulated from the exterior zone. Instant coagulation at the orifice can take place if the iaterior fluid is a strong coagulant. In such an event, an internal skin is formed and the fiber draw-down rate is relatively low.  [c.149]

The bleaching of cotton textiles was once the single largest use for hydrogen peroxide, with lesser quantities used to bleach wool, silk (qv), cotton—synthetic blends and some vegetable and animal fibers (qv). The stabilized alkaline hydrogen peroxide bleaching of cotton and cotton blend fabrics is done in continuous processes. A primary advantage for hydrogen peroxide in this industry is that it has no effect on many modem dyes. It has been estimated that 85% of all cotton fabrics are bleached with hydrogen peroxide. Added to its other advantages, hydrogen peroxide is a nonpolluting oxidant which is of significant and increasing importance.  [c.481]

Other fibrous and porous materials used for sound-absorbing treatments include wood, cellulose, and metal fibers foamed gypsum or Pordand cement combined with other materials and sintered metals. Wood fibers can be combined with binders and dame-retardent chemicals. Metal fibers and sintered metals can be manufactured with finely controlled physical properties. They usually are made for appHcations involving severe chemical or physical environments, although some sintered metal materials have found their way into architectural appHcations. Prior to concerns regarding its carcinogenic properties, asbestos fiber had been used extensively in spray-on acoustical treatments.  [c.312]

This is unacceptable in communication systems operating at 1.55 )J.m, the minimum loss region of optical fibers, over distances on the order of 100 km and data rates as high as 10 gigabites per second (Gb/s). This is because light of different wavelengths travels in optical fibers at slightly different speeds. This property of optical fibers results in time spreading of optical pulses traveling down the fiber and carrying information in digital form. Eventually it is not possible to distinguish between the individual pulses. The only way to avoid this problem is to work with lasers emitting light in a single and very narrow mode. The most effective of such devices is the distributed feedback (DFB) laser shown in a cross section of Figure 12.  [c.135]

Alternatively, a fiber optic bundle can be used in place of the pipe. In a fiber optic bundle, a matrix of smaU (50—100 -lm) fiber optic strands are arranged such that the ordering of the strands at one end is equivalent to that on the other end. Therefore an image focused on one end with lenses is transmitted to the other end. Light is typicaUy sent down some of the fibers not used for image transmission to provide illumination.  [c.48]

The properties of electrocetamics ate related to their ceramic microstmcture, ie, the grain size and shape, grain—grain orientation, and grain boundaries, as well as to the crystal stmcture, domain configuration, and electronic and defect stmctures. Electronic ceramics ate often combined with metals and polymers to meet the requirements of a broad spectmm of high technology apphcations, computers, telecommunications, sensors (qv), and actuators. Roughly speaking, the multibillion doUat electronic ceramics market can be divided into sis equal parts as shown in Eigute 1. In addition to Si02-based optical fibers and displays, electronic ceramics encompass a wide range of materials and crystal stmcture families (see Table 1) used as insulators, capacitors, piezoelectrics, magnetics, semiconductor sensors, conductors, and the recendy discovered high temperature superconductors. The broad scope and importance of the electronic ceramics industry is exemplified in Eigure 2, which schematically displays electroceramic components utilized in the automotive industry. Currentiy, the growth of the electronic ceramic industry is driven by the need for large-scale integrated circuitry giving rise to new developments in materials and processes. The development of multilayer packages for the microelectronics industry, composed of multifunctional three-dimensional ceramic arrays called monohthic ceramics (MMC), continues the miniaturization process begun several decades ago to provide a new generation of robust, inexpensive products.  [c.308]

There are several basic types of evaporative cooling devices. Among them are spray air washers, ceU washers, and wetted media air coolers. Intimate contact between the spray water and the flowing air causes heat and mass transfer between the air and the water. CeU washers obtain intimate air—water contact by passing the air through ceUs packed with glass, metal, or fiber screens. Wetted media coolers contain evaporative pads, made usuaUy of aspen wood fibers, and a water circulating pump to lift the sump water to a distributing system from which it mns down through the pads and back into the sump. Washers are commonly available from 1 to 118 m /s (2000—250,000 fF /min) capacity depending on the type however, there is no limit to si2es that can be constmcted. Air velocity, air dry-bulb, air wet-bulb, water spray density, spray pressure, and other design factors must be considered for each appHcation.  [c.362]

High Strength Fibers by Gel Spinning. Gel spinning has been used for some time to produce high strength fibers from ultrahigh molecular weight polyethylene. Spectra 900 and 1000 fibers from Ahied and Dyneema SK60 and SK65 fibers from DSM are two commercial examples. Extensive studies have also been carried out on polypropylene, poly(vinyl alcohol), and polyacrylonitrile. Commercial gel spun acryhcs are not fat off.  [c.284]

In the Ahied process two solvents ate used. The first has low volatihty and is designed to be an effective solvent for the high molecular weight FAN. The resultant solution or xetogel is extmded with a jet stretch of lOx or less through an ak gap into a cooling bath where the extmdate is converted into gel fibers. Gelation is important because it restricts chain mobhity and prevents chain entanglements from forming as the solvent is extracted. The first solvent is extracted with a volatile solvent, and the solvent is then removed by evaporation. The fibers are drawn in several stages starting with the usual jet stretch at the spinneret face. Subsequent drawing is done after the solvent is removed in stages of increasing temperature from 130 to 230°C. Typical wet spinning solvents ate used for solvent 1 and water is used as solvent 2. The AUied and DSM processes ate similar, but DSM adds zinc chloride to the spinning solution to prevent phase separation and aid in drawing. The total draw ratio may be anywhere from 8-29x, with the highest tenacities achieved at the highest draw ratios. Table 3 compares the properties of gel spun FAN with other high performance fibers (qv) (71,72).  [c.284]

Antisoiling Fibers. Low dirt-absorbing fibers have been made by incorporating fluorinated comonomers, and porous fibers with reduced staining tendencies have been made from acrylic copolymers containing sulfonated comonomers. Anti-soiling properties can also be achieved by using finishes, either by treating the fiber during spinning, or by applying finishes directly to the fabric. Treatment of acrylic fabrics with sodium hydroxide also gives improved soil release (92). Soil adhesion and soil removal (93) and the effect of fiber properties on soiling resistance (94) have been reviewed. An example of an acrylic stain-resistant fiber process is Stainorain, jointly developed by Pharr Yarn and Du Pont. Using Du Pont s Teflon technology, the fibers are impregnated with a water—oil repeUant and stain-resistant chemical. This is done early in the fiber production process to lock in the protective properties. The fiber is designed for use in knitted garments for children and active sportswear such as golf and ski sweaters (95).  [c.285]

In the spunbond process (Fig. 10), an aspiratory is used to draw the fibers in spinning and directiy deposit them as a web of continuous, randomly oriented filaments onto a moving conveyor belt. In the meltblown process (Fig. 11), high velocity air is used to draw the extmded melt into fine-denier fibers that are laid down in a continuous web on a collector dmm.  [c.317]

Although this first route was simple in concept, it proved slow in operation, difficult to scale up safely, and relatively uneconomical compared with the other routes. Denitration of the fibers, necessary to allow safe use wherever the fabrics may risk ignition, spoiled their strength and appearance. Nevertheless, Chardoimet earned and truly deserved his reputation as the Eather of Rayon. His process was operated commercially until 1949 when the last factory, bought from the Tubize Co. in the United States in 1934 by a Bra2iUan company, burned down.  [c.344]

Zinc salts are added to the spin bath to slow down the regeneration reaction by forming a less easily decomposed 2inc cellulose xanthate intermediate. This allows greater stretch levels to be appHed and results in fibers with thicker skins. There is still uncertainty as to whether the 2inc cellulose xanthate gel acts by hindering acid ingress or water loss. High levels of 2inc in the spin-bath allow the production of tough fibers for tire reinforcement and industrial use.  [c.348]

The strongest fibers were made usiag formaldehyde additions to the spia bath while usiag a mixed modifier system (26) or usiag highly xanthated viscoses (50% + CS2). Formaldehyde forms an. -methylol derivative with xanthate which decomposes slowly permitting high levels of stretch. It also reacts with the cellulose backbone to form cross-links that render the fiber high ia modulus and low ia extension. Unfortunately, problems associated with formaldehyde side reactions made the processes more expensive than first thought, and the iaevitable brittieness which results whenever regenerated cellulose is highly oriented restricted the fibers to nontextile markets. The commercial operations were closed down ia the late 1960s.  [c.349]

Toyobo s Tufcel provides an excellent example of how a modem polynosic fiber process, probably the most difficult viscose process to mn efficientiy, operates (35). On-line process control allows only four persons per shift to make 10,000 t/yr of a variety of special fibers including Flame Retardant, Deep Dying (two types). Activated Carbon Fiber, and Super Fiae 0.55 dtex (0.5 denier). Aik-cell and mixing soda quaUty are maintained by pressiags soda centrifugation, filtration, and dialysis to remove 90% of the hemiceUulose. Ion-exchange membranes are used to give 50 times the life and twice the efficiency of the old dialyzer bags used ia tire-yarn production. Dissolution of the 500 DP xanthate is augmented by cmmb-gtinders on the churn outiets and by in-line homomixers, which together reduce the dissolution time from three hours to one. Spinnerets for the finer yams have 40-p.m holes, and these are protected by automatic backflush filters removing gels down to 15 p.m diameter.  [c.349]

By the mid-1980s a different approach to the production of fine fibers with novel cross sections became possible. Noncircular spinneret holes, eg, rectangular slots, allowed the large-scale production of flat fibers down to 2.2 dtex (2 den) (Eig. 6a). These 1-shaped fibers were capable of replacing the inflated hoUow fibers in textile appUcations, providing similar levels of bulk, warmth, and handle while having a much more regular shape. They were foUowed by the development of soUd Y-shaped and X-shaped multil imbed fibers (48) (Eig. 6b) which performed like SI fiber but had much lower levels of water imbibition than the inflated version. Their shape and relative stiffness enabled them to absorb more fluid between, as opposed to inside, the fibers. They were therefore as absorbent in use as the inflated versions (49,50) but did not require the extra process chemicals, and were easier to wash and dry in production and use. They are the most important bulky rayons now in production.  [c.350]

Also in 1974, ACl started the direct spinning of Bemliese nonwoven fabrics using the same conveyor belt washing technique (70). This process uses wide spinnerets and spinning cells to produce a curtain of filaments which fall in the spinning liquor onto the conveyor. The conveyor is oscillated from side to side in order to lay the continuous fibers down in sinusoidal waves. After washing, the webs, which have strength resulting from the self-bonding nature of the fibers as-spun, can be further strengthened and finished by hydroentanglement.  [c.351]

The fibers ia bast and leaf fiber plants are iategral with the plant stmcture, providing strength and support. In bast fiber plants, the fibers are next to the outer bark ia the bast or phloem and serve to strengthen the stems of these reedlike plants. They are strands miming the length of the stem or between joiats (Fig. 1). To separate the fibers, the natural gum binding them must be removed. This operation is called retting (controlled rotting). For most uses, particularly for textiles, this long composite-type strand fiber is used directiy however, when such fiber strands are pulped by chemical means the strand is broken down iato much shorter and finer fibers, the ultimate fibers shown ia Figure 1.  [c.357]

Heckling. The bundles are hackled or combed to separate the short and long fibers. This is done by drawiug the fibers through sets of pius, each set finer than the previous one. As a result the fibers are further cleaned and aligned parallel to one another.  [c.360]

Examination of physical evidence provides two subtie and different types of conclusion as may be itiustrated by the following examples. Consider a hit-and-mn case involving an automobile (6) and a decedent. An examination of the victim s clothing turns up some blue paint. A suspect vehicle is located the vehicle is blue. Infrared spectroscopy of the surface, solubility tests in various solvents, and microscopic examination of cross sections demonstrate that the composition of the paint from the vehicle and from paint samples recovered on the victim s clothing ate identical (7). A laboratory report stating that the two specimens are identical is likely to prejudice a jury into concluding that the paints are identical, and therefore, it was the defendant s car that hit the pedestrian. A more carefully worded laboratory report would explain that the samples ate identical and that the paint could have come from the car in question, or any other similarly painted car. Many automobile manufacturers use the same blend of paint on thousands, and likely hundreds of thousands of vehicles. No matter how much testing is done, the results are the same the samples are indistinguishable. This concept is known as class or group characteristics. AH members of a class or group have identical characteristics. Types of physical evidence which exhibit class characteristics are paint (qv), glass (qv), fibers (qv), fabric, building material, etc. This type of physical evidence is said to be identified. The best that chemical and physical examinations can ever do is to place items into groups of similarly manufactured items. It is not possible to differentiate one item of evidence as being uniquely distinguishable from another.  [c.484]

Needle-PunchedFa.brics, In the two-stage needle-punching process, a fibrous web is placed into a machine which is equipped with a series of specially designed tevetsed-batbed needles. The web of material is passed between two plates. As the fabric passes between the plates, the needles punch down through the top plate and fabric, reorienting the fibers and resulting in entanglement of the fibers. Fabric weights from this process generally range between 60 and 700 g/m (1.7 to 20 02/yd ). Fabric thickness ranges between 0.4 and 5 mm (15 to 200 mils).  [c.258]

Secondary Operations. In secondary forming, a piece of preformed glass is reheated and reworked into the finished product. Repressing of optical blanks in precision molds below the primary pressing temperature is sometimes done by lens manufacturers who do not melt their own glass. Redrawing of tubing and cane (rods) is called for when manufacturing bundles of thin fibers, as in channel amplifiers, or long, thin single fibers, as in optical waveguides. Sagging flat glass, eg, automotive windshields, is accompHshed at temperatures near the softening point so that the glass bends to fit a form made from a refractory or metal. Lamp-working and sealing are often either hand or automated operations in which the glass (rod or tubing) is heated near its working point (10 lO" Pa-s or 10 —10 P) and formed to the desired shape. Novelties, labware, and glass-to-metal wire seals for electrical and electronic appHcations are common lampworked articles. Precision tubing with inside-diameter variations as small as 30 )J.m/m length are made by shrinking. This is done by vacuum-coUapsing the hot tube over a mandrel which is withdrawn when the glass has cooled (87).  [c.312]

The fibers of aromatic PODs are known to have a combination of good properties, such as strength and stiffness, fatigue resistance, and relatively low density, in the range of 1.2 to 1.4 g/cm. PODs have been used to improve the heat resistance of many synthetic fibers. This is usually done by dissolving the POD in sulfuric acid and then treating the fibers with this solution. Poly -phenylene-l,3,4-oxadia2ole) is the most commonly used commercial polyoxadia2ole, and the fiber spun from this polymer is called Oksalon.  [c.535]

In the mid-1970s it was discovered at the Dutch States Mines Co. (DSM) that through an ingenious new method of gel spinning ultrahigh molecular weight polyethylene it was possible to produce fibers having twice the tenacity of Kevlar, which was then considered to be the strongest known fiber (14). The discovery was important not only because of the exciting 3.8 N/tex (44 gf/den) strengths these new fibers displayed, but also because it clearly demonstrated that factors other than monomer polarity were critical in controlling fiber performance characteristics. These high performance polyethylene fibers (HPPE) produced by the DSM subsidiary company, Stamicarbon, are called Dyneema and those produced by the AUiedSignal Corp. in the United States are sold under the trade name of Spectra 1000. The commercial products have somewhat lower strengths than the laboratory fibers but stiU are in the high 2.6 N/tex (30 gf/den) range.  [c.68]

High Strength Fibers. Super fibers or fibers with very high tenacities and Young s moduH have been defined as those with a tenacity of at least 2.5 GPa (255 kgf/mm ) and a modulus of at least 55 GPa (5600 kgf/mm ) (29). Fibers meeting these criteria are aramids such as Kevlar and Twaron, gel spun polyethylene such as Dyneema and Spectra, and various carbon fibers and aromatic Hquid—crystalline polyesters such as Vectran. Representative appHcations are for antibaUistic clothing, building materials, aerospace, and as reinforcing material in composites for various appHcations.  [c.70]

Interpenetrated Wall Matrix. Ion-exchange hoUow fibers can be produced by polymerising an ionic monomer within the porous waU matrix of a hoUow fiber. Eor example, 4-vinylpyridine has been polymerised in a porous waU matrix of polyacrylonitrile (PAN) hoUow fiber (21), and monomers containing sulfonic acid moieties have been polymerised in the waU matrix of polysulfone to yield ion-exchange hoUow fibers (employed in Doiman-type dialysis). Requirements of such a fabrication are (/) the monomers should not dissolve or plasticise the polymer from which the fibers are made (2) the heat generated during the polymerisa tion and contraction prior to the formation of new interpenetrating polymer should be minimised and (J) the polymerisation should not occur within the lumen (and hence cause plugging of the fiber). The fabrication of such fibers is accompUshed by forcing the monomers into the matrix under pressure while maintaining a fiow of gas or Uquid in the bore. High charge densities can be obtained by cross-linking the polymer network for example, by employing sulfonated phenol-formaldehyde as the ionic species, highly cross-linked resin within the fiber waU is obtained (22). Drawbacks of such fibers are brittleness.  [c.151]

The morphology of the ME tape can be seen in Figure 21. In the cross-sectional microstmcture, prepared by ion milling, the so-called banana-shaped morphology is clearly visible. Due to the shadowing effect the density of such a film is not high and the micromagnetic behavior is probably a mixture of domain-wall motion and rotation of the magnetization. The stmctural analysis of the tape provides the following data. The thickness of the magnetic layer is about 130 nm and a regular stmcture composed of very fine fibers is observed (thickness 3—10 nm). The columns make an angle of 37° relative to the plane of the film. Auger electron spectroscopy (aes) has shown an average composition of Co Ni QO (104,105).  [c.185]

Sihca-based glass fiber, used in the telecommunications industry, is the most mature of the fiber technologies. SiUca fiber has achieved an attenuation of 0.2 dB/km at 1.55 p.m, its theoretical limit. The fiber is strong and inexpensive. SiUca fibers can transmit well from 0.25 to 2 p.m, but different formulations are used for the uv and in ends of that range. For somewhat longer wavelengths, fluoride glasses are the preferred materials, and the fluorozirconates are the best developed of these (see Fluorine compounds, inorganic). Most fluoride glasses are a mixture of several fluorides, so they have become known by acronyms based on the first letters of the chemical symbols for the constituent metal elements. For example, ZBLAN fiber contains on a mol % basis 55.8% ZrF 14.4% BaF2, 5.8% LaF, 3.8% AIF., and 20.2% NaF. Fiber composition governs the transmission range. ZBLAN, for example, transmits down to 3.8 p.m, but other fluorozirconates can reach 5.5 p.m, and some BaF2/ThF4 glasses reach 7 p.m (9). The fluoride glasses are not as strong as the siUca glasses and are moisture sensitive. State-of-the-art fluoride fibers have minimum losses below 1 dB/km, but commercial fibers have losses of a few tens of dB/km. Chalcogenide fibers are required for even longer wavelengths. Most chalcogenide fibers are non stoichiometric mixtures of sulfur, selenium, or tellurium with one Group 15 (V) element or one Group 14 (IV) element, or both. Chalcogenide fibers are not as strong as fluoride fibers, but are not moisture sensitive. The transmission ranges of some chalcogenides extend to about 16 p.m. State-of-the-art fibers have minimum losses of a few tens of dB/km, but commercial ones have minimum losses of about 1 dB/m. The principal source of attenuation in chalcogenide fibers is absorption by impurities, particularly oxygen, hydrogen, and water. As a result, attenuation in a chalcogenide fiber is highly wavelength dependent, showing absorption peaks from the various impurities (8).  [c.193]

Fiber optic transmission works differendy from copper cable transmission. Instead of metal wire conducting an electrical charge, hair-thin glass or plastic fibers conduct light that is sent by rapid flashing on and off (digitally). The light can travel in more than one beam (multimode) or in one monomode beam, by bouncing off the inner walls of the hoUow fiber (3). The coating layer cladding helps redect light down the fiber.  [c.323]

Wet spinning of this type of hoUow fiber is a weU-developed technology, especiaUy in the preparation of dialysis membranes for use in artificial kidneys. Systems that spin more than 100 fibers simultaneously on an around-the-clock basis are in operation. Wet-spun fibers are also used widely in ultrafiltration appUcations, in which the feed solution is forced down the bore of the fiber. Nitto, Asahi, Microgon, and Romicon aU produce this type of fiber, generaUy with diameters of 1—3 mm.  [c.71]

Several deposition techniques are available immersion plating, electroplating, spray deposition, chemical vapor deposition (CVD), and physical vapor deposition (PVD) (see Thin films). Dipping or immersion plating is similar to infiltration casting except that fiber tows are continuously passed through baths of molten metal, slurry, sol, or organometaUic precursors. Electroplating (qv) produces a coating from a solution containing the ion of the desired material in the presence of an electric current. Fibers are wound on a mandrel, which serves as the cathode, and placed into the plating bath with an anode of the desired matrix material. The advantage of this method is that the temperatures involved are moderate and no damage is done to the fibers. Problems with electroplating involve void formation between fibers and between fiber layers, adhesion of the deposit to the fibers may be poor, and there are limited numbers of alloy matrices available for this processing. A spray deposition operation typically consists of winding fibers onto a foil-coated dmm and spraying molten metal onto them to form a monotape. The source of molten metal may be powder or wire feedstock which is melted in a flame, arc, or plasma torch. The advantages of spray deposition ate easy control of fiber alignment and rapid solidification of the molten matrix. In a CVD process, a vaporized component decomposes or reacts with another vaporized chemical on the substrate to form a coating on that substrate. The processing is generally carried out at elevated temperatures.  [c.197]


See pages that mention the term Dyne fibers : [c.352]    [c.258]    [c.260]    [c.274]    [c.284]    [c.308]    [c.349]    [c.359]    [c.193]    [c.313]    [c.71]   
Chemistry of Petrochemical Processes (2000) -- [ c.369 ]