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TECHNICAL MATERIALS V. GLASS

Glass:

Glass is a hard, fragile, transparent and amorphous inorganic material usually produced by man. Artificial glass is used to make windows, lenses, bottles and a wide variety of products.

RAW MATERIALS: The glass is obtained at about 1,500 ° C from silica sand (SiO₂), sodium carbonate (Na₂CO₃) and limestone (CaCO₃).

The term "crystal" is very often used as a synonym for glass, although it is incorrect in the scientific field because glass is an amorphous solid (its molecules are not arranged in a regular way) and not a crystalline solid. In daily life these two concepts are mixed because both elements are transparent.

Properties of glass: It is a HARD material (very resistant to scratching), FRAGILE (breaks easily), TRANSPARENT or almost, since if you do not add suitable components during cooking it is greenish (like cider bottles), it is INERT and It doesn’t contaminate the liquids that it contains and is very resistant to the attack of chemical products that would attack other types of containers like metal or plastic. It is a bad conductor of electricity and bad (but no so bad) of the heat.

Glass manufacturing: Glass is made from a mixture of silica, fluxes such as sodium carbonate and stabilizers, such as lime. This mixture can contain recycled crushed glass. These raw materials are loaded into the large furnace (continuous production) by means of a hopper. The oven is heated with gas or oil burners. The flame must reach a sufficient temperature, and for this the combustion air is preheated in stoves built with refractory bricks before it reaches the burners. The mixture melts (melting zone) to about 1,500 ° C and advances to the cooling zone. In this zone, the temperature of the oven reaches of 1200 to 800 ° C. The glass thus obtained is need a posterior process, (stretching, floating or blowing) depending on its final use.

 Furnace details:

FLAT GLASS:

Today, almost all window glass is mechanically manufactured from a pool of molten glass by floating technology. This glass is solidified by floating it in a molten tin pool. Then it is brought to an annealing furnace. In this furnace the glass is cooled in a controlled way. After this, it is cut into sheets

HOLLOW GLASS:

Bottles, jars and other glass containers are made by an automatic process that combines the pressing (to form the open end) and blowing (to form the hollow body of the container). In a typical machine for blowing bottles, molten glass is dropped into an inverted narrow mould (blank mould) and it is pressed by a plunger (sometimes it needs to be blown too) into the lower end of the mould, giving to the bottle the first shape. This half-formed bottle (blank shape) is held by the neck, inverted and passed to a second finishing mould, in which a jet of air gives it its final dimensions.  This process can still be done by hand in artisan workshops by blowing with air.

Making glass bottles:

GLASS FIBER:

It is possible to produce glass fibers - which can be woven like textile fibers - by stretching molten glass to diameters less than one hundredth of a millimetre. Both long and continuous yarns can be produced as short fibers of 25 or 30 centimetres in length. Once woven to form fabrics, fiberglass turns out to be an excellent material for curtains and upholstery because of its chemical stability, strength and resistance to fire and water. By impregnating glass fibers with plastics we can form a composite type that combines the solidity and chemical stability of the glass with the impact resistance of the plastic. It is used to make body of vehicles, boats or canoes, etc.

OPTICAL FIBER:

It is a medium of transmission usually used in data networks; A very thin wire of transparent material, generally glass trhough which pulses of light are sent which represent the data to be transmitted. The fibers are widely used in telecommunications, since they allow sending great amount of data to a great distance, with speeds similar to those of radio waves and superior to the ones of conventional wires. They are the transmission medium par excellence to be immune to electromagnetic interference, are also used for local networks, where high speed are needed. The materials of which the optical fiber is made are two concentric glass tubes, inside which the light will circulate. It is a very delicate and expensive process, where temperatures of arround 2000 ° C can be reached since a glass with high quartz content is needed.

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