DALLA BETTA GROUP S.R.L.

GLASS

Other Specialties

Common experience teaches that monolithic glass is a fragile material. If it is instead spun to diameters of less than a tenth of a millimeter, it loses its characteristic fragility to become a material with high mechanical resistance and resilience. The fragility of common glass is due to the large number of defects in crystallization that act as microfractures and stress concentration zones, on the contrary, glass fiber does not have many defects, so it achieves considerable mechanical resistance. The main technology used today to form glass fibers is the direct fusion method; this method uses furnaces divided into three sections: - in the first part the molten glass arrives, which is homogenized and from which gaseous inclusions are removed; - a second refining section, where the temperature decreases (from 1370 to 1200 °C) to increase the density of the melt; - finally the section that is located directly above the stations for the production of the fibers. The glass is then passed through heated platinum-iridium dies, which contain 400 to 8,000 holes. The amount of glass above the holes, the viscosity of the melt, the number and size of the holes, and the speed at which the wires are drawn all affect the diameter of the filaments produced. In the sizing phase, at the exit of the die, each filament is treated with a sizing agent; the sizing agent is made of organic materials dispersed in water and is designed to give the glass wire the characteristics necessary for the final processing. The sizing treatment helps improve the mechanical properties of the composite materials and their resistance to aging. The fibers, collected in bobbins, are then put in an oven to eliminate solvents and water associated with the sizing application. A completely similar technique uses glass beads with a diameter of ¾ inch that are heated and brought to near melting point to be drawn through the dies. Among the main characteristics of glass fibers are: - Good stability at high temperatures - Excellent resistance to thermal shock - Good dimensional stability - Good mechanical resistance (Glass maintains its mechanical properties up to 50 percent of its resistance capacity at 375 °C and up to 25 percent at 538 °C) - Low thermal conductivity - Incombustible - Excellent flexibility - Good chemical resistance Depending on their composition, they are divided into: E Glass and AR Glass

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