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Glass fibers have been known for thousands of years, since the first stick poked into the molten sand desert nomads built their fires upon. Since 1938 glass textiles have been commercially produced with properties not unlike other textiles typically used, being perfectly acceptable for textile uses such as braiding, wrapping, weaving, and knitting. Glass-fiber textile yarns can be knotted and extremely pliable.
Glass textiles have an enticing potential for production with indigenous lunar resources, and the author feels that lunar glasses in general will be at least as useful as plastics to be produced on Mars. Silica and calcium carbonate are the main components, with varying amounts added of sodium oxide and sodium carbonate, potassium carbonate, aluminum hydroxide or aluminum oxide, or magnesia. The alkali carbonate components decompose to the respective oxides at the high temperatures experienced.
Glass fibers are produced by fusing the materials in a solar furnace to make a molten glass. This melt is either directly extruded by various methods through perforated tips on a platinum base plate, as with Nylon, or formed into glass marbles first. The fifty or more resultant filaments can be drawn to a chosen size before being woven into a yarn for making a textile. A direct-melt process also exists, both methods producing continuous or staple fiber (cut to a specific length for spinning yarn).
Glass fiber textiles do not absorb dirt, which makes it useful for the dust problems of the lunar environment. It is not effected by sunlight, where other fibers are weakened or bleached. It does not show swelling or shrinkage.
The coefficient of friction between glass and glass is high, causing abrasion problems. The movement of fibers against each other cause fractures, which lead to a hairy fabric. However, both of these issues can be minimized by coating with lubricants, metals, or finishes to reduce friction.
Glass does not absorb moisture, which causes apparel worn near the skin to be clammy and uncomfortable. The water absorptive qualities of cotton is what makes it more comfortable then polyester, for example. Nevertheless, if abrasion issues can be solved with lunar-available metal coatings, lunar textiles would be suitable for jackets, vests, aprons, gloves, footwear, baggage.
Although glass is very resistant to most chemicals, but some soluble components, such as alkali silicates, can be leached out by water, thus reducing the tensile strength of glasses without a low alkali content. Glass is disintegrated by alkalis, and is attacked by phosphoric acid and certain strong mineral acids. The material completely resists odor, insects, and biological degradation in general.
Water leaching out alkali silicate ingredients complicates the production of glass-glass composites, one of the most exciting prospects for lunar building and consumer goods materials. In glass-glass composites, glass fiber with a high melting point is embedded in a glass matrix with a lower melting point. For this purpose, a lead dopant to lower the matrix melting point is ideal; however lead rarely occurs at concentrations of even 10 parts per million (in breccias). The alternative of using sodium and potassium, common on the Moon and able to lower the melting point almost as much, needs to be made practical for use in moist environments. One possibility would be to sputter a coating of metal such as aluminum onto any surfaces to be used near water or moisture. Perhaps a better workaround would be to sacrifice some of the strength of the material in leaching all the alkali dopants back out right at the factory for reuse.
Peter Kokh has suggested fiberglass reinforced ceramics, and fiberglass reinforced concrete is already a reality. He has also suggested sulfur impregnated fiberglass, as sulfur impregnated fabrics in general have some very useful applications, and there is plenty of sulfur on the Moon. Silicones have also been used in composites with glass fiber. The "fiberglass" commonly used on Earth in bathtubs and sailboat hulls is actually a composite of glass fiber and an epoxy resin.
The material has the highest strength-to-weight ratio of any fiber, and is completely nonflammable. Starting at about 205 C, glass fibers lose their strength with heat. At 370 C the material's tensile strength is halved, and at 538 C strength is reduced by a factor of four. Glasses soften into a viscous liquid rather than melt in the usual sense of the term.
Glass fiber has very high thermal conductivity, suggesting use for electrical cloths and wiring insulation. It can also be used for sound insulation, or to add strength to insulation. Despite its thermal conductivity, "fiberglass insulation", actually glass wool using coarse, short and matted fibers, also proves cheap and effective on Earth by trapping air between the filaments.
Potential uses for glass textiles on the Moon include furniture and vehicle upholstery, curtains, wall coverings, fabrics to be covered such as on mattresses, etc. Coated fabrics can use glass textiles, and it can be used for reinforcement in cloths or paper. Tape (with in-situ produced adhesives), screening, and braided products are also possible. It is suitable for use in the raw lunar environment as a sunshade textile among many other possibilities.
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