What Is Glass Fiber?
Glass fiber is a mass of very fine strands of glass. When ordinary glass is spun into thin threads it is strong and bendable, unlike normal glass objects, which are brittle and break easily. These silky strands of glass can be woven into a material or massed together like cotton-wool. Glass fiber does not decay or corrode. It is a good insulator and a poor conductor of electricity. Curtains made of this material do not rot in damp conditions or in sunlight.
Now that technical dyeing problems have been overcome, glass fiber can be patterned. Many plastics tend to crack or bend under stress or impact, but combining them with strands of glass fiber results in very light, strong and useful materials. Glass fiber increases their strength in much the same way as concrete is reinforced with steel rods. These mixtures are molded to make such things as aircraft parts, car bodies, boats and fishing rods.
Coarse mats of glass fiber are used for filters and washers, and blankets of the material provide good insulation for houses. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling. In 1893, Edward Drummond Libbey exhibited a dress at the World’s Columbian Exposition incorporating glass fibers with the diameter and texture of silk fibers. This was first worn by the popular stage actress of the time Georgia Cayvan. Glass fibers can also occur naturally, as Pele’s hair.
Glass wool, which is one product called “fiberglass” today, was invented in 1932–1933 by Russell Games Slayter of Owens-Corning, as a material to be used as thermal building insulation. It is marketed under the trade name Fiberglas, which has become a generalized trademark. Glass fiber when used as a thermal insulating material, is specially manufactured with a bonding agent to trap many small air cells, resulting in the characteristically air-filled low-density “glass wool” family of products.
Glass fiber has roughly comparable mechanical properties to other fibers such as polymers and carbon fiber. Although not as strong or as rigid as carbon fiber, it is much cheaper and significantly less brittle when used in composites. Glass fibers are therefore used as a reinforcing agent for many polymer products; to form a very strong and relatively lightweight fiber-reinforced polymer (FRP) composite material called glass-reinforced plastic (GRP), also popularly known as “fiberglass”. This structural material product contains little or no air or gas, is denser, and is a much poorer thermal insulator than is glass wool.
Glass fiber has increased in popularity since the discovery that asbestos cause’s cancer and its subsequent removal from most products. However, the safety of glass fiber is also being called into question, as research shows that the composition of this material (asbestos and glass fiber are both silicate fibers) can cause similar toxicity as asbestos.
1970s studies on rats found that fibrous glass of less than 3 micrometers in diameter and greater than 20 micrometers in length is a “potent carcinogen”. Likewise, the International Agency for Research on Cancer found it “may reasonably be anticipated to be a carcinogen” in 1990. The American Conference of Governmental Industrial Hygienists, on the other hand, says that there is insufficient evidence, and that glass fiber is in group A4: “Not classifiable as a human carcinogen”.
The North American Insulation Manufacturers Association (NAIMA) claims that glass fiber is fundamentally different from asbestos, since it is man-made instead of naturally occurring. They claim that glass fiber “dissolves in the lungs”, while asbestos remains in the body for life. Although both glass fiber and asbestos are made from silica filaments, NAIMA claims that asbestos is more dangerous because of its crystalline structure, which causes it to cleave into smaller, more dangerous pieces, citing the U.S. Department of Health and Human Services:
Synthetic vitreous fibers [fiber glass] differ from asbestos in two ways that may provide at least partial explanations for their lower toxicity. Because most synthetic vitreous fibers are not crystalline like asbestos, they do not split longitudinally to form thinner fibers. They also generally have markedly less biopersistence in biological tissues than asbestos fibers because they can undergo dissolution and transverse breakage.
A 1998 study using rats found that the biopersistence of synthetic fibers after one year was 0.04–10%, but 27% for amosite asbestos. Fibers that persisted longer were found to be more carcinogenic.