COVER STORY
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Nozzle drawing- The glass fed in is melted in a heated melt tub at 1250–1400oC. Then, it emerges at the bottom of the melt tub from nozzle holes of 1–25 mm diameter and it is taken off and drawn. The filaments solidify and are finished and wound. One can find them in the shops as various kinds of “glass silk”.Nozzle blowing- The same as with nozzle-drawing, glass balls are melted in the tub. The melt emerging from the nozzle holes is then taken by pressed air, which draws the liquid glass so as to make fibres of 6–10 um diameter. A fluttering effect is caused by the flow of pressed air, which results in fibres of lengths from 50 to 300 mm. A lubricant is put on and the fibres are laid down on a sieve drum which sucks them in. The dry web received is held together by the long fibres, the short ones lying in between them as a filling material. Then, the slivers of glass fibre material are cut. Rod drawing- By means of a burner, bundles of glass rods are melted at their bottom ends. This results in drops which, as they fall down, draw filaments after them. The filaments are taken by a rotating drum, a squeegee laying them down onto a perforated belt. Thus, a dry web is received which can be wound as glass fibre slivers. Machine performance being limited by the number of glass rods fed in, the rotating drum may be combined with nozzle-drawing, which results in drum-drawing. This multiplies machine performance. The dry web is again laid down onto a perforated belt and solidified or, after winding it so as to receive slivers, cut for further processing on machines producing wet laid nonwovens. Using and processing glass fibres is not without any problems. For example, fine pieces of broken fibres may disturb if the work place is not well prepared for the purpose. Using the nonwovens to manufacture glass-fibre reinforced plastics, it is important the surface of the plastic material is fully even. Ends of fibre looking out may be pulled out or loosened by outward stress (temperature, gases, liquids), which may influence material characteristics. In some cases, it is advisable to cover up such layers of glass fibre with suitable chemical fibres.
PROPERTIES: 1. Mechanical strength: Fibreglass has a specific resistance greater than steel. So, it is used to make high-performance fabrics 2. Electrical characteristics: Fibreglass is a good electrical insulator even at low thickness. 3. Incombustibility: Since fibreglass is a mineral material, it is naturally incombustible. It does not propagate or support a flame. It does not emit smoke or toxic products when exposed to heat. 4. Dimensional stability: Fibreglass is not sensitive to variations in temperature. It has a low coefficient of linear expansion. 5. Compatibility with organic matters: Fibreglass can have varying sizes and has the ability to combine with many synthetic resins and certain mineral matrices like cement. 6. Non-rotting: Fibreglass does not rot and remains unaffected by the action of rodents and insects. 7. Thermal conductivity: Fibreglass has low thermal conductivity making it highly useful in the building industry. 8. Dielectric permeability: This property of fibreglass makes it suitable for electromagnetic windows.
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