Fibrous form of glass, developed in the 1930s. Liquid glass issues in fine streams through hundreds of fine nozzles, and the solidifying streams are gathered into a single strand and wound onto a spool. Strands can be twisted into yarns, woven into fabrics, or chopped into short pieces and then bonded into mats. Glass filaments and yarns add strength and electrical resistivity to molded plastic products. Glass fabrics are used as electrical insulators and as reinforcing belts in automobile tires. Discontinuous fibres are formed into wools, mats, or boards, commonly used in buildings, appliances, and plumbing.
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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 Fiberglass, which has become a genericized trademark.
The technique of heating and drawing glass into fine fibers has been known for millennia; however, the use of 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 the 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. Owens-Corning is still the major fiberglass producer in the market today. Two types of fibre glass most commonly used are S-glass and E-glass.E-glass have good insulation properties and it will maintain its properties up to 1500 degree F(815 deg C). S-glass has a high tensile strength and is stiffer than E-glass.
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.
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 chemical properties are needed. It is usual to introduce impurities into the glass in the form of other materials to lower its working temperature. These materials also impart various other properties to the glass which may be beneficial in different applications. The first type of glass used for fiber 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 is an alumino-borosilicate glass. This was the first glass formulation used 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 for use when tensile strength is the most important property. C-glass was developed to resist attack from chemicals, mostly acids which destroy E-glass. T-glass is a North American variant of C-glass. A-glass is an industry term for cullet glass, often bottles, made into fiber. AR-glass is alkali resistant glass. Most glass fibers have limited solubility in water but it is very dependent on pH. Chloride ions will also attack and dissolve E-glass surfaces. A recent trend in the industry is to reduce or eliminate the boron content in the glass fibers.
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 235 mm long, elongates under its own weight at 1 mm/min when suspended vertically and heated at the rate of 5°C per minute". The strain point is reached when the glass has a viscosity of 1014.5 poise. The annealing point, which is the temperature where the internal stresses are reduced to an acceptable commercial limit in 15 minutes, is marked by a viscosity of 1013 poise.
Glass strengths are usually tested and reported for "virgin" fibers: those which have just been manufactured. The freshest, thinnest fibers are the strongest because the thinner fibers are more ductile. The more the surface is scratched, the less the resulting tenacity. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber. Humidity is an important factor in the tensile strength. Moisture is easily adsorbed, and can worsen microscopic cracks and surface defects, and lessen tenacity.
In contrast to carbon fiber, glass can undergo more elongation before it breaks. There is a correlation between bending diameter of the filament and the filament diameter. The viscosity of the molten glass is very important for manufacturing success. During drawing (pulling of the glass to reduce fiber circumference) the viscosity should be relatively low. If it is too high the fiber will break during drawing, however if it is too low the glass will form droplets rather than drawing out into fiber.
The bushings are what make the capital investment in fiber glass production expensive. The nozzle design is also critical. The number of nozzles ranges from 200 to 4000 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 correct 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.p. 94 The surface tension of the glass is what influences the formation of the meniscus. For E-glass it should be around 400 mN per m.
The attenuation (drawing) 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.
Glass-reinforced plastic (GRP) is a composite material or fiber-reinforced plastic made of a plastic reinforced by fine glass fibres. Like graphite-reinforced plastic, the composite material is commonly referred to by the name of its reinforcing fibers (fiberglass). Chemosetting plastics are normally used for GRP production – most often polyester (using butanone as a catalyst), but vinylester or epoxy are also used. The glass is can be in the form of chopped strand mat (CSM) or a woven fabric.
As with many other composite materials (such as reinforced concrete), the two materials act together, each overcoming the deficits of the other. Whereas the plastic resins are strong in compressive loading and relatively weak in tensile strength, the glass fibers are very strong in tension but have no strength against compression. By combining the two materials, GRP becomes a material that resists both compressive and tensile forces well. The two materials may be used uniformly or the glass may be specifically placed in those portions of the structure that will experience tensile loads.
Corrugated fiberglass panels are also widely used for outdoor canopy or greenhouse construction. These are thin, rigid panels with a wavy or zig-zag cross-section, usually a pale green or yellow color (although they are also available in other colors). They are usually available in widths of 2-4 feet and lengths of 6-16 feet. Overlapping one wave pattern on each edge is often sufficient to prevent most water or wind penetration through the seams.