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 resulting composite material , properly known as glass-reinforced plastic (GRP) or glass-fiber reinforced epoxy (GRE), is called "fiberglass" in popular usage.

Glassmakers throughout history have experimented with glass fibers, but mass manufacture of fiberglass was 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 (sic), see also genericized trademark .

Formation

Glass fiber is formed when thin strands of silica based or other formulation glass is extruded into many fibers with small diameters suitable for textile processing. Glass is unlike other polymers in that, even as a fiber, it has little crystalline structure (see amorphous solid ). The properties of the structure of glass in its softened stage are very much like its properties when spun into fiber. One definition of 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 as 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 (Loewenstein, 2). Owens-Corning is still the major fiberglass producer in the market today.

Chemistry

The basis of textile grade glass fibers is silica , SiO 2 . In its pure form it exists as a polymer, (SiO 2 ) 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 an ordered structure (Gupta, 544). In the polymer it forms SiO 4 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 (glass and quartz ) 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
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 alumino-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 from 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 minuteâ€

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