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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
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 viscosityContinuum mechanics Fluid dynamics Viscosity is a measure of the resistance of a fluid to deformation under shear stress. It is commonly perceived as "thickness", or resistance to pouring. Viscosity describes a fluid's internal resistance to flow and may 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 stapleStaple has several meanings: a staple is a formed metal fastener used to secure sheets of material a foodstuff that forms the basic constituent of a diet is a Staple food staple is the raw material, or its length and quality, of fibre from which textiles. When the two companies joined together to produce and promote fiberglass, they introduced continuous filamentA filament is a fine, thinly spun thread, fiber, or wire. Originally the term referred primarily to animal or vegetable structures, but with advances in technology it is frequently used to refer to human-made things including filaments of incandescent lig glass fibers (Lowenstein, 2). Owens-Corning is still the major fiberglass producer in the market today.
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 pointThe melting point of a solid is the temperature at which it changes state from solid to liquid. When considered as the temperature of the reverse change, it is referred to as the freezing point . For example, the melting point of the element mercury is 23 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).
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 – 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).