Fiberglass or fibreglass is material made from extremely fine fibers of glass. It is widely used in the manufacture of insulation and textiles. It is also used as a reinforcing agent for many plastic products, the result being a composite material called glass-reinforced plastic or GRP, also known as glass-fiber reinforced epoxy (GRE).
  
   Glassmakers throughout history had experimented with glass fibers, but innovations such as fiberglass were only made possible with the advent of finer machine-tooling. In 1893, Edward Drummond Libbey exhibited a dress at the World Columbian Exposition incorporating glass fibers with the diameter and texture of silk fibers. What is commonly known as "fiberglass" today, however, was invented in 1938 by Russell Games Slayter of Owens-Corning as a material to be used as insulation. It is marketed under the trade name Fiberglas. The term 'fiberglass' is often used, rather imprecisely, for glass-reinforced plastic (GRP) - see genericized trademark
  
   Formation
   Glass fiber is formed when thin strands of silica based or other formulation glass is extruded into fibers with small diameters suitable for textile processing. Glass is unlike other polymers in that it has little crystalline structure and can be considered a substance frozen in its amorphous stage. The properties of the structure of glass in its softened stage are very much like its properties when spun into fiber. One definition is, "glass is an inorganic substance in a condition which is continuous with, and analogous to the liquid state of that substance, but which, as a result of a reversible change in viscosity during cooling, has attained so high a degree of viscosity and to be for all practical purposes rigid (Loewenstein, 4)."
   The technique of heating and drawing glass into fine fibers has been known to exist for thousands of years, however, the concept of using these fibers for textile applications is more recent. The first commercial production of fiberglass was in 1936. In 1938, Owens Illinois Glass Company and Corning Glass Works joined to form Owens-Corning Fiberglas Corporation. Until this time all fiberglass had been manufactured as staple. When the two companies joined together to produce and promote fiberglass, they introduced continuous filament glass fibers (Lowenstein, 2). Owens-Corning is still the major fiberglass producer in the market today.
  
   Chemistry
   The basis of textile grade glass fibers is silica, SiO2. In its pure form it exists as a polymer, (SiO2)n. It has no true melting point but softens up to 2000?C, where it starts to degrade. At 1713?C, most of the molecules can move about freely. If the glass is then cooled quickly, they will be unable to form and ordered structure (Gupta, 544). In the polymer it forms SiO4 4- groups which are arranged as a tetrahedron with the silicon atom at the center and four oxygen atoms at the corners. These atoms then form a network bonded at the corners by sharing the oxygen atoms.
   The vitreous and crystalline states of silica have similar energy levels on a molecular basis, also implying that the glassy form is extremely stable. In order to induce crystallization, it must be heated to temperatures above 1200?C for long periods of time (Loewenstein, 6).
  
  
   Molecular Structure of Glass
   Although pure silica is a perfectly viable glass and glass fiber, it must be worked with at very high temperatures which is a drawback unless its specific properties are needed. It is usual to introduce impurities in the form of other materials into the glass to lower its working temperature. These other materials also impart various other properties to the glass which may be beneficial in different applications. The first type of glass used was soda-lime glass or A glass. It was not very resistant to alkali. A new type, E-glass was formed that is alkali free (< 2%) and an alunimo-borosilicate glass (Volf, 338). This was the first glass produced for continuous filament formation. E-glass still makes up most of the fiberglass production in the world. Its particular components may differ slightly in percentage, but must fall within a specific range. The letter E is used because it was originally for electrical applications. S-glass is a high strength formulation when tensile strength is the most important property. C-glass was developed to resist attack form chemicals, mostly acids which destroy E-glass (Volf, 340).
   Since E-glass does not really melt but soften, the softening point is defined as, ¡°the temperature at which a 0.55 ¨C 0.77 mm diameter fiber 9.25 inches long, elongates under its own weight at 1 mm/min when suspended vertically and heated at the rate of 5?C per minute¡± (Lubin, 152). The strain point is where the glass has a viscosity of 10 14.5 poise. The annealing point, which is the temperature where the internal stresses are reduced to an acceptable commercial limit in 15 minutes. The viscosity at this point should be 10 13 poise (Lubin, 152).
  
   Properties
   Glass fibers are useful because of their high ratio of surface area to weight. However, the increased surface makes them much more susceptible to chemical attack. Humidity is an important factor in the tensile strength. Glass strengths are usually tested and reported of virgin fibers which have just been manufactured. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber (Gupta, 546). However, moisture is easily adsorbed. Moisture can worsen microscopic cracks and surface defects and lessen tenacity. The more the surface is scratched, the less the tenacity is (Volf, 351). The freshest, thinnest fibers are the strongest and this is thought to be due to the fact that it is easier for thinner fibers to bend. In respect to carbon fibers, glass has a higher elongation (Gupta, 546).
   The viscosity of the molten glass is very important. During drawing the viscosity is relatively low. If it is too high the fiber will break during drawing. If it is too low the glass will form droplets rather than drawing. The different dopants added to the glass affect its viscosity (Volf, 358). For E-glass, the acceptable range of viscosities is 10 3.2 to 10 3.8 dPa s. The batch temperature should be around 1090?C and the temperature at the nozzle should be around 1450?C (Volf, 359)
  
   Manufacturing Processes
   There are two main types of glass fiber manufacture and two main types of glass [[Media:fiber product. First, fiber is made either from a direct melt process or a marble remelt process. Both start with the raw materials in solid form. They are mixed together and melted in a furnace. Then, for the marble process, the molten material is sheared and rolled into marbles which are cooled and packaged. The marbles are then taken to the manufacturing facility where they are inserted into a can and remelted. Then the molten glass goes to the bushing to be formed into fiber. In the direct melt process, the molten glass in the furnace goes right to the bushing for formation. (Lubin, 149)
   The bushing is the most important part of the machinery. This is a small metal furnace containing nozzles for the fiber to be formed through. It is almost always made of platinum alloyed with rhodium for durability. Platinum is used because the glass melt has a natural affinity for wetting it. When bushings were first used they were 100% platinum and the glass wetted the bushing so easily it ran under after exiting the nozzle and accumulated on the underside. Also, due to its cost and the tendency to wear, it was alloyed with rhodium. In the direct melt process, the bushing serves as a collector for the molten glass. It is heated slightly to keep the glass at the correct temperature for fiber formation. In the marble melt process, the bushing acts more like a furnace as it melts more]] of the material. (Loewenstien, 91)
   The bushings are what make the capital investment in fiber glass production expensive. The nozzle design is important also. The number of nozzles ranges form 200 to 1600 in multiples of 200. The important part of the nozzle in continuous filament manufacture is the thickness of its walls in the exit region. It was found that inserting a counterbore here reduced wetting. Today, the nozzles are designed to have a minimum thickness at the exit. The reason for this is that as glass flows through the nozzle it forms a drop which is suspended from the end. As it falls, it leaves a thread attached by the meniscus to the nozzle as long as the viscosity is in the range for fiber formation. The smaller the annular ring of the nozzle or the thinner the wall at exit, the faster the drop will form and fall away and the lower its tendency to wet the vertical part of the nozzle (Loewenstein, 94). The surface tension of the glass is what influences the formation of the meniscus. For E-glass it should be around 300 mN m-1 (Volf, 360).
   The attenuation speed is important in the nozzle design. Although slowing this speed down can make coarser fiber, it is uneconomic to run at speeds for which the nozzles were not designed (Loewenstein, 94).
   In the continuous filament process, after the fiber is drawn, a size is applied. This size helps protect the fiber as is wound onto a bobbin. The particular size applied relates to end-use. While some sizes are processing aids, others make the fiber have an affinity for a certain resin, if the fiber is to be used in a composite (Lubin, 100). Size is usually added at 0.5 ¨C2.0% by weight. Winding then takes place at around 1000 m min ¨C1 (Gupta, 544).
   In staple fiber production, there are a number of ways to manufacture the fiber. The glass can be blown or blasted with heat or steam. Usually there fibers are made into some sort of mat. The most common process used is the rotary process. The glass enters the rotating spinner and due to centrifugal force are thrown out horizontally. The air jets push them down vertically and binder is applied. Then the mat is vacuumed to a screen and the binder is cured in the oven (Mohr, 13).
   End uses for regular fiber glass are mats, insulation, reinforcement, heat resistant fabrics, corrosion resistant fabrics and high strength fabrics.
  
   Bibliography
   Gupta, V.B. and V.K. Kothari. Manufactured Fibre Technology. Chapman and Hall. London. 1997.
   Loewenstein, K.L. The Manufacturing Technology of Continuous Glass Fibers. Elsevier Scientific. New York. 1973.
   Lubin, George. Handbook of Fiberglass and Advanced Plastic Composites. Robert E. Krieger. Huntingdon NY. 1975.
   Mohr, J. G. and W. P. Rowe. Fiberglass. Van Nostrand Reindhold. Atlanta. 1978.
   Volf, Milos B. Technical Approach to Glass. Elsevier. New York. 1990.
  
   Glass-reinforced plastic (GRP), is a composite material made of a plastic reinforced by fine fibers made of glass. The plastic is most often polyester, but other plastics, like epoxy (GRE), are also sometimes used.
   GRP/GRE is a versatile material with many uses. Its first main application was for building of boats, where it gained acceptance in the 1950s, and now plays a dominant role. But its use has broadened over the years, and it is used extensively within the automotive and sport equipment sectors. GRE is also used to make pipes for drinking water, sewers, chemicals, and so on. The term "fiberglass" is often used, rather imprecisely, for GRP. 
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   Composite materials (or composites for short) are engineering materials made from two or more components. One component is often a strong fibre such as fiberglass, kevlar or carbon fibre that gives the material its tensile strength, while another component (often called a matrix) is often a resin such as polyester or epoxy that binds the fibres together and renders the material stiff and rigid.
   Examples of composite materials:
   Fibre reinforced plastics:
   Glass-fibre reinforced plastic or GRP
   Carbon-fibre reinforced plastic or CRP (see carbon fiber)
   metal matrix composites or MMCs
   Chobham armour (see composite armour)
   plywood
   Weatherbest
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   The tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before it breaks.
   Tensile strength is an important concept in engineering, especially in the fields of material science, mechanical engineering and structural engineering.
   Once past the elastic limit, the material will not relax to its initial shape after the force is removed. See Hooke's law and modulus of elasticity. The tensile strength where the material becomes plastic is called yield tensile strength. This is the point where the deformation (strain) of the material is unrecovered, and the work produced by external forces is not stored as elastic energy but will lead to contraction (see Poisson), cracks and ultimately failure of the construction. Clearly, this is a remarkable point for the engineering properties of the material since here the construction may lose its loading capacity or undergo large deformations. On the stress-strain curve below this point is in between the elastic and the plastic region.
   The ultimate tensile strength (UTS) of a material is the limit stress at which the material actually breaks, with sudden release of the stored elastic energy (released as noise and/or heat and/or more cracks e.g. for brittle materials). This point is the fracture marked X on the curve below.
  
   For steel, the elastic limit is at about 0,2% and the breaking point is at 25% of the total (relative) extension In steel constructions, the maximum allowable tensile stress at any point in the construction is 2/3 of the yield strength (or 0,2% deformation stress in metals or alloys without clearly defined yield stress). This comes down to a safety factor of 1.5.
   Tensile strength is measured in units of force per unit area. In the SI system, the unit is newton per square metre (N/m² or Pa - Pascal). The U.S customary unit is pounds per square inch (or PSI).
   The breaking strength of a rope is specified in units of force, such as newtons, without specifying the cross-sectional area of the rope. This is often loosely called tensile strength, but this not a strictly correct use of the term.
   In brittle materials such as rock, concrete, cast iron, glass or soil, tensile strength is negligible compared to the compressive strength and it is assumed zero for most engineering applications.
   Tensile strength can be measured for liquids as well as solids. For example, when a tree draws water from its roots to its upper leaves by transpiration, the column of water is pulled upwards from the top by capillary action, and this force is transmitted down the column by its tensile strength. Air pressure from below also plays a small part in a tree's ability to draw up water, but this alone would only be sufficient to push the column of water to a height of about ten metres, and trees can grow much higher than that. (See also cavitation, which can be thought of as the consequence of water being "pulled too hard".)
   Some typical tensile strengths of some materials:
  
   Material Yield strength(MPa) Ultimate strength(MPa)
   Structural steel ASTM-A36 250 400
   Steel, high strength alloy ASTM A-514 690 760
   Stainless steel AISI 302 - Cold-rolled 520 860
   Cast iron 4.5% C, ASTM A-48 - 170
   Aluminum Alloy 2014-T6 400 455
   Copper 99.9% Cu 70 220
   Titanium Alloy (6% Al, 4% V) 830 900
   Nylon, type 6/6 45 75
   Rubber - 15
   Marble - 15
   Single-walled carbon nanotubes have the highest tensile strength of any material yet measured, with the highest single measurement of a nanotube being 63 GPa. As of 2004, however, no macroscopic object constructed using a nanotube-based material has had a tensile strength remotely approaching this figure, or substantially exceeding that of high-strength materials like kevlar.
  
   A polymer is a long, repeating chain of atoms, formed through the linkage of many molecules called monomers. The monomers can be identical, or in complex polymers such as proteins the monomers have one or more substituted chemical groups, this gives them the ability to inhibit other conformations than random coil by the process of self-assembly. Although most typically organic (based on carbon chains), there are also many inorganic polymers.
   The term polymer covers a large, diverse group of molecules, including substances from proteins to high-strength kevlar fibres. A key feature that distinguishes polymers from other large molecules is the repetition of units of atoms (monomers) in their chains. This occurs during polymerization, in which many monomer molecules link to each other. For example, the formation of polyethene involves thousands of ethene molecules bonding together to form a chain of repeating -CH2- units:
  
   Polymers are often named in terms of their monomer units, for example polyethylene is represented by:
  
   Because polymers are distinguished by their constituent monomers, polymer chains within a substance are often not of equal length. This is unlike other molecules in which every atom is acounted for, each molecule having a set molecular mass. Differing chain lengths occur because polymer chains terminate during polymerization after random intervals of chain lengthening (propagation).
   Proteins are polymers of amino acids. From a dozen to some hundred of the (about) twenty different monomers form the chain, the sequence of monomers determining the shape and activity of the final protein. But there are active regions, surrounded by, as is believed now (Aug 2003), structural regions, whose sole role is to expose the active region(s) (there may be more than one on a given protein). So the absolute sequence of amino acids is not important, as long as the active regions are expressed (being accessible from the outside) properly. Also, whereas the formation of polyethylene occurs spontaneously given the right conditions, the manufacture of biopolymers such as proteins and nucleic acids requires the help of catalysts (substances that facilitate or accelerate reactions.) Since the 1950s, catalysts have also revolutionised the development of synthetic polymers. By allowing more careful control over polymerization reactions, polymers with new properties, such as the ability to emit coloured light, have been manufactured.
   Intermolecular forces
   The attractive forces between polymer chains play a large part in determining a polymer's properties. Because polymer chains are so long, these interchain forces are amplified far beyond the attractions between conventional molecules. Also, longer chains are more amorphous (randomly oriented). Polymers can be visualised as tangled spaghetti chains - pulling any one spaghetti strand out is a lot harder the more tangled the chains are. These stronger forces typically result in high tensile strength and melting points.
   The intermolecular forces in polymers are determined by dipoles in the monomer units. Polymers containing amide groups can form hydrogen bonds between adjacent chains; the positive hydrogen atoms in N-H groups of one chain are strongly attracted to the oxygen atoms in C=O groups on another. These strong hydrogen bonds result in, for example, the high tensile strength and melting point of kevlar. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogens in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so ethene's melting point and strength are lower than kevlar's, but polyesters have greater flexibility.
   Ethene, however, has no permanent dipole. The attractive forces between polyethylene chains arise from weak van der Waals forces. Molecules can be thought of as being surrounded by a cloud of negative electrons. As two polymer chains approach, their electron clouds repel one another. This has the effect of lowering the electron density on one side of a polymer chain, creating a slight positive dipole on this side. This charge is enough to actually attract the second polymer chain. Van der Waals forces are quite weak, however, so polyethene melts at low temperatures.
   Branching
   During the propagation of polymer chains, branching can occur. In radical polymerization, this is when a chain curls back and bonds to an earlier part of the chain. When this curl breaks, it leaves small chains sprouting from the main carbon backbone. Branched carbon chains cannot line up as close to each other as unbranched chains can. This causes less contact between atoms of different chains, and fewer opportunities for induced or permanent dipoles to occur. A low density results from the chains being further apart. Lower melting points and tensile strengths are evident, because the intermolecular bonds are weaker and require less energy to break.
   Stereoregularity
   Stereoregularity or tacticity describes the isomeric arrangement of functional groups on the backbone of carbon chains. Isotactic chains are defined as having substituent groups aligned in one direction. This enables them to line up close to each other, creating crystalline areas and resulting in highly rigid polymers.
   In contrast, atactic chains have randomly aligned substituent groups. The chains do not fit together well and the intermolecular forces are low. This leads to a low density and tensile strength, but a high degree of flexibility.
   Syndiotactic substituent groups alternate regularly in opposite directions. because of this regularity, syndiotactic chains can position themselves close to each, though not as close as isotactic polymers. Syndiotactic polymers have better impact strength than isotactic polymers because of the higher flexibility resulting from their weaker intermolecular forces.
   Copolymerization
   Copolymerization is polymerization with two or more different monomers. Already mentioned are the twenty amino acid monomers that make up protein chains. Copolymerization of different monomers can result in varied properties of polymers, just as different amino acids result in different shapes of proteins. For example, copolymerising ethene with small amounts of hex-1-ene is one way to form linear low density polyethene (LLDPE) (See Polyethylene). The C4 branches resulting from the hexene lower the density and prevent such large crystalline regions within the polymer as in HDPE. This means that LLDPE can withstand strong tearing forces whilst remaining flexible.
  
   Polymer characterization
   A variety of laboratory techniques are used to determine the properties of polymers. Techniques such as wide angle xray scattering, small angle xray scattering, and small angle neutron scattering are used to determine the crystalline structure of polymers. Gel permeation chromatography is used to determine the number average molecular weight, weight average molecular weight, and polydispersity. FTIR is used to determine composition. Thermal properties such as the glass transition temperature and melting point can be determined by differential scanning calorimetry and dynamic mechanical analysis. Thermal degradation followed by analysis of the fragments is one more technique for determining the possible structure of the polymer.
   See also: Polymerization -- Biopolymer -- Condensation polymer -- Synthetic polymer -- Glass transition temperature
  
   mesh is similar to fabric or a web in that it has many connected or weaved pieces. In clothing, a mesh is often defined as fabric that has a large number of closely-spaced holes, such as is common practice for modern sports jerseys.
   Meshes are often used to screen out unwanted things, such as insects. Wire screens on windows and mosquito netting can be considered as types of meshes. Wire screens can also be used to shield against radio frequency radiation, as in their use in microwave ovens and Faraday cages. On a larger scale, in terms of the spaces in between, chain-link fence can also be considered a type of mesh.
   In computing, there are at least two uses of the term mesh. Probably the oldest term relates to 3D modeling, and is a synonym for wireframe models. A highly interconnected network of computers or networking hardware can also be considered a mesh. See mesh network.
   The term screen has a number of meanings:
   A window screen is a wire mesh that covers a window opening to keep out insects even when the window is open.
   Screen is also a synonym for film or movie as in the expression "Silver Screen" or the Screen Actors Guild, or as a verb as in "the movie was recently screened".
   A screen is also a viewing surface, such as a white surface (of cloth, or a wall) for slide and film projection, or the viewing surface of a cathode ray tube or liquid crystal display (LCD). See display device.
   A screen can be a transportable or permanently mounted panel or connected series of panels intended to obscure or hide the space behind it, used for visual privacy.
   In naval ship formations, a screen of small, fast ships (such as destroyers) is used to protect larger ships such as battleships and aircraft carriers from attack by similar ships, torpedo boats or submarines. The objective of the screening ships is to destroy attackers before they can approch within torpedo range of the larger ships.
   Screen-printing, or Silk-Screening is a method of printing and a screen is a piece of equipment used in this process.
   The verb screen is to examine something for defects or dangers.
   A genetic screen in genetics is a procedure or test to identify and select individuals that possess a particular kind of phenotype
   In a telecommunications, computing, or data processing system, to examine entities that are being processed to determine their suitability for further processing.
   It can also describe a nonferrous metallic mesh used to provide electromagnetic shielding.
   Screening can be to reduce undesired electromagnetic signals and noise by enclosing devices in electrostatic or electromagnetic shields.
   GNU screen is a computer program which multiplexes computer terminals.
   Yarn is a long continuous length of interlocked fibers, suitable for use in the production of textiles, sewing, knitting, weaving and ropemaking. Yarn can be made from any number of synthetic or natural fibers. Very thin yarn is referred to as thread. Yarns are made up of any number of plys, each ply being a single thread these threads being twisted (plied) together to make the final yarn.
   In some cases, thread may be monofilament, in which case it is a single fiber. The only natural fiber that is counted as monofilament is silk.
   Yarn is manufactured by either a spinning or air texturizing (commonly referred to as taslanizing) process.
  
   Spools of thread
   Yarn manufacturing was one of the very first processes that was industrialized. Yarn used for fabric manufacture is made by spinning short lengths various types of fibers. Synthetic fibers which have high strength,artificial lusture,and fire retardant qualities are blended with natural fibers which have good water absorbance and skin comforting qualities, in different proportions to manufacture yarn for fabric. The most widely used blends are cotton-polyster and wool-acrylic fiber blends.
   Yarn is usually measured by weight. In the United States, balls of yarn are usually sold in three-ounce, four-ounce, six-ounce, and eight-ounce skeins. In Europe the units used by textile engineers is often tex, which is the weight in grams of a kilometer of yarn. Many other units have been used during the last centuries each industry creating its own for internal purposes and these escaping into the public domain.
  
   A Yarn is also a type of story.
   It is usually a long, rambling and involved story or a very lengthy joke with the main source of humour in the punchline. This type of story is also known as a Shaggy dog story or a campfire yarn.
   see : urban legend