Fiberglass consists of numerous extremely fine fibers of glass. Although experimented with throughout history actual glass fibers were not mass produced until the invention of finer machine tooling.

A dress with glass fibers was first worn in 1893 by stage actress Georgia Cayvan. Russell Games Slayter invented, in 1938, what is commonly known as fiberglass today. It is commonly used for insulation. Carbon fiber is also a somewhat similar but more expensive technology used in place of fiberglass when high strength and low weight is necessary.

To form glass fibers thin strands of silica-based glass is extruded into many fibers with small diameters that are suitable for textile processing. The process of creating these fibers has been known for a while; however, the use of the fibers for textile application is more recent. In 1936 the first commercial production of fiberglass took place. After Owens-Illinois Glass Company and Corning Glass Works joined they introduced continuous filament glass fibers. Owens-Corning is still the major fiberglass producer in the market today.
E-glass is most commonly used although A-glass, E-CR-glass, C-glass, D-glass, R-glass, and S-glass are also used. Silica is the basis for textile-grade glass fibers. Its pure form exists as a polymer and has no true melting point. Since the vitreous and crystalline states of silica have similar energy levels on a molecular basis it is implied that the glassy form is extremely stable. It has to be heated to temperatures above 2,190 °F for long periods of time.

Pure silica is viable glass and glass fiber but has to be worked with at very high temperatures. In order to lower the necessary work temperature other materials are introduced. Soda lime glass, A-glass, was the first type of glass used for fiber. E-glass, which is alkali free, was the first glass formulation used for continuous filament formation. The E-glass makes up most of the fiberglass production in the world. E is used since the fibers were originally used for electrical applications. Chloride ions will also attack and dissolve E-glass surfaces. S-glass is used when tensile strength is most important. C-glass is resistant to attack from chemicals along with T-glass which is the North American variant of C-glass. A-glass refers to cullet glass made into fiber.

The fibers are useful due to their high ratio of surface are to weight and by being able to trap air within them making blocks of glass fiber good thermal insulation. The strength is tested and reported right after manufacturing. The more the surface is scratched the less the resulting tenacity. Humidity is also an important factor in tensile strength because the moisture can worsen cracks and surface defects which lessen tenacity.

Glass is capable of undergoing more elongation before it breaks than carbon fiber. For manufacturing success one of the important keys is the viscosity of molten glass. This viscosity should be relatively low during drawing because if it is too high the fiber will break and if it is too low the glass will form droplets rather than drawing out in the fiber.

Fiberglass gained in popularity when it was found that asbestos causes cancer, however, recent research shows that the composition of this material causes similar toxicity as asbestos. These stats are debatable. The North American Insulation Manufacturers Association believes that since fiberglass is man-made it differs from naturally occurring asbestos. The NAIMA claims asbestos to be more dangerous due to its crystalline structure. Since fiberglass has synthetic vitreous fibers they don’t split longitudinally to form thinner fibers like asbestos. They also have less bio-persistence in biological tissues than asbestos fibers.

Fiberglass can be used in mats, thermal insulation, electrical insulation, sound insulation, reinforcement of various materials, tent poles, sound absorption, automobile bodies, hockey sticks, surfboards, boat hulls, and paper honeycomb. It can be used in medical purposes in casts.

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