Glass manufacturing

Glass manufacturing

1. Glass Manufacturing

2. An amorphous, rigid and brittle material, typically transparent or translucent, made by fusing sand with soda, lime, and sometimes other ingredients; and cooling rapidly. What is glass?

3. Glass manufacturing materials can be divided into 5 categories Glass former Flux Modifier Coloring agents Fining agents Cullet ( broken glass pieces) Raw Materials

4. Raw Materials …….. Cont Glass former: one of the most important components present in any glass Silica (SiO2), boric oxide (B2O3) and phosphoric oxide (P2O5) are the most common type of glass formers present in oxide glass

5. The use of silica glass is wide but melting temperature of silica is too high (1600-1725ºC). To reduce the processing temperature of silica, different types of flux such as Na2O and PbO can be used Raw Materials …….. Cont

6. Raw Materials …….. Cont The addition of fluxes to silica reduces the overall cost of glass processing but results in degradation of properties. Sodium carbonate and calcium carbonate are common fluxes. Potash glass is more dense than soda glass. To overcome this problem, different property modifiers or intermediates such as boron, sodium, magnesium, titanium, and calcium can be used to modify the properties of glass

7. Colorants are used to control the color in the final glass. The amount of iron oxides ( impurities) present in the glass results in unintentional change in color of glass. The other types of colorants used are gold and silver. These types of colorants change glass color by forming colloids in glasses Raw Materials …….. Cont

8. As the raw materials melt and react inside the furnace, carbon dioxide and water emission takes place which causes formation of bubbles . F ining agents such as arsenic, antimony oxides, potassium and sodium nitrates are added to raw materials to remove bubbles from the melt The high temperature and low viscosity is maintained to raise the gas bubbles at the upper surface of the melt and hence removed from the melt Fining is important because it controls the homogeneity of glass by eliminating bubbles. Raw Materials …….. Cont

9. The manufacture of glass is in four phases : ( 1) preparation of raw material, ( 2) melting in a furnace, (3) forming and ( 4) finishing. Manufacturing Steps

10. Process Flow Diagram

11. Depending upon the applications, there are different processes of forming the glass. The most common type of glass forming process can be categorized as : Flat glass Glass fibers Glass tubing Glass forming

12. Flat glass, sheet glass, or plate glass is made by two processes. The processes are float glass process and rolled glass process Flat Glass

13. R ibbon of glass is made by pouring molten glass from the furnace to a bed of molten metal such as tin, lead and low melting point alloys under controlled atmosphere. Float glass process

14. In the drawing or rolling process, the continuous stream of molten glass from a furnace passes through a pair of water cooled rollers Rolled glass process

15. Fiberglass is available in two types continuous glass fiber and short glass fiber (glass wool) . The first one is used in fabrication of composite materials and latter one is used for thermal insulation . Glass fibers

16. Continuous glass fiber is produced by drawing molten glass through multiple orifices Continuous Glass Fibers

17. In glass wool process , the molten glass is ejected from a rotating head by centrifugal spraying process Short glass fibers

18. In this process, molten glass flows around a rotating hollow cone-shaped or cylindrical mandrel through which air is supplied continuously to avoid the collapsing of glass tube while the glass is drawn out by set of rollers . Glass Tubing

19. Soda-lime glass Fused silica glass Lead glass Borosilicate glass Types and applications of glass

20. M ain constituent of practically all commercial glass is sand. Sand by itself can be fused to produce glass but the temperature at which this can be achieved is about 1700°C. Adding other minerals and chemicals to sand can considerably reduce the melting temperature . The addition of sodium carbonate (Na 2 CO 3 ), known as soda ash, to produce a mixture of 75% silica (SiO 2 ) and 25% of sodium oxide (Na 2 O), will reduce the temperature of fusion to about 800°C due to sodium silicate. Soda-lime glass

21. However, a glass of this composition is water-soluble and is known as water glass. To give the glass stability, other chemicals like calcium oxide ( CaO ) and magnesium oxide ( MgO ) are needed. These are obtained by adding limestone which results in a pure inert glass . Soda-lime glass is a mixture of sodium silicate and calcium silicate. Soda-lime glass (Water Glass)

22. Simplest type off glass, consists mainly of silica Made by heating silica to a molten liquid,the liquid is then cooled rapidly to form an amorphous solid Fused silica glass

23. Commonly known as Crystal or lead crystal Made by using lead oxide instead of calcium oxide, and potassium oxide instead of all or most of the sodium oxide G lass containing at least 24% PbO can be described as lead crystal. Glass containing less than 24% PbO , is known simply as crystal glass. Lead glass has a high refractive index making it sparkle brightly and a relatively soft surface Lead Glass

24. G lass in the form of ovenware and other heat resisting ware, better known under the trade name Pyrex . Borosilicate glass (or sodium-borosilicate glass) is made mainly of silica (70-80%) and boric oxide (7-13%) with smaller amounts of the alkalis (sodium and potassium oxides) and aluminium oxide . As it doesn't break when changing temperature quickly.  sodium borosilicate glass is widely used across the chemical industry, pharmaceutical sector for laboratory apparatus Borosilicate glass

25. T he basic flat glass product that is the first result of the float process. It is common glass that tends to break into large, jagged shards. It is used in some end products and often in double-glazed windows. Also the starting material used to produce more advanced products through further processing such as laminating, toughening, coating, etc Annealed Glass

26. Glass can fracture due to stress concentration. To avoid the fracture of glass, local high compressive stresses are induced near the surfaces. This is done by thermal toughening of glass . Heating the glass plate to 650ºC after which rapidly cooling the outer surface by air blasts . Due to which thin compressive layer is created at the outer surface and the center of the glass becomes the region of tensile stresses. This causes the self-equilibrium. The glasses used in glazed door and making tabletops are made by this process and is termed as toughened or safety glass . Toughened or tempered glass

27. Made of two or more layers of glass with one or more "interlayers" of polymeric material bonded between the glass layers. Laminated glass is produced using one of two methods: Poly Vinyl Butyral (PVB) laminated glass (Ethyl Vinyl Acetate (EVA) or Polyurethane (PU) are also used) Cast in Place (CIP) laminated glass is made by pouring a resin into the space between two sheets of glass that are held parallel and very close to each other . Safety and security Rather than shattering on impact, laminated glass is held together by the interlayer. This reduces the safety hazard associated with shattered glass fragments Laminated Glass