[Topic 6] Glass Industries Flashcards
It is a rigid, undercooled liquid having no definite melting point and is sufficiently high viscosity (greater than 10^12 Pa*s) to prevent crystallization.
Glass
It is formed by combining nonvolatile inorganic oxides through the decomposition and fusion of alkali and alkaline earth compounds, sand, and other ingredients.
Glass
The resulting product has a random atomic structure.
Glass
Properties of glass (8)
- completely vitrified product
- Transparent
- Hard
- Has the ability to be molded or shaped when heated
- Has high resistance to chemical attack
- Good electric insulator
- Brittle
- greater compressive strength than tensile strength.
Uses of Glass (9)
- Windows and doors
- Food and drinks packaging
- Tableware
- Insulation
- Conservatory
- Flacon for cosmetics and pharmaceutical
- Interior design and furniture
- Automotive and transport
- Medical technology, optical glass, biotechnology, etc.
Major ingredients for glass making (3)
- Sand (Silica - in the past)
- Lime
- Soda Ash
Important factor in glass making (2)
- Viscosity of molten oxides
- Relation between viscosity and composition
Classes of commercial glasses (7)
- Fused Silica or Vitreous Silica
- Alkali Silicates
- Soda-lime Glass or Soft Glass
- Lead Glass or Flint Glass
- Borosilicate Glass or Hard Glass
- Special Glasses
- Glass Fibers
It is made by pyrolysis of silicon tetrachloride or fusion of quartz and sand.
Fused Silica or Vitreous Silica
Fused Silica or Vitreous Silica is sometimes called as _______ .
Quartz Glass
True or False: Fused or Vitreous Silica has high expansion and can handle high temperature.
False: Low expansion
True or False: Fused or Vitreous Silica stays strong in heat better than other glasses.
True
Fused or vitreous silica is exceptionally transparent with _________ .
Ultraviolet light
It is made by melting sand and soda ash.
Alkali silicates
Composition ranges from Na2OSiO2 to Na2O4SiO2
Alkali silicates
True or False: Silicate of soda solution (or water glass) is used as paper adhesive and for fireproofing.
True
Higher alkaline types are used in _________ and ____________.
- Laundering
- Soap making
Constitutes 95% of all manufactured glass.
Soda-lime glass or soft glass
It is used for containers, flat glass, automobile, and other windows, tumblers, and tableware.
Soda-lime glass or soft glass
In the liquor trade, how do glassware was made resulting in difficult melting yet chemically resistant glass.
Made with high alumina and lime, low alkali
It was used as a decolorizer for better color.
Selenium
It is derived from replacing calcium oxide with lead oxide.
Lead or Flint Glass
Utilized in optics for its high refractive index and dispersion.
Lead or Flint Glass
High lead(PbO) content yields superior _______.
Cut glass
It is employed in electric light bulbs, neon signs, and radiotrons for its high electrical resistance.
Lead or Flint Glass
Lead or Flint Glass are ideal for _____________.
Nuclear radiation shielding
It has low expansion coefficient, superior resistance to shock, excellent chemical stability, and high electrical resistance.
Borosilicate or Hard Glass
Notable example of borosilicate or hard glass.
Pyrex laboratory glassware
It is colored and coated, opal, translucent, safety, optical photochromic glasses, and glass ceramics.
Special Glasses
True or False: Special glasses have fixed compositions because it does not depend on the final product desired.
False: Varying compositions depending on the final product desired
It is produced from special glass compositions that are resistant to weather conditions.
Glass Fibers
True or False: Glass fibers have large surface area which makes them vulnerable to moisture in air.
True
True or False: Glass Fibers has high in silica (55%), high in alkali.
False: Low in silica (55%). low in alkali
Raw materials for glass making (8)
- Sand
- Soda (Na2O)
- Lime
- Feldspars
- Borax
- Salt Cake
- Cullet
- Refractory Blocks
It determines the glass factory’s location.
Sand
True or False: For sand, it should consist of nearly pure quartz.
True
True or False: Iron content should be higher than 0.45% for tableware; higher than 0.015% for optical glass.
False: below 0.45 for tableware; below 0.015% for optical glass
It is supplied by dense soda ash.
Soda (Na2O)
Other sources of soda (3)
- Sodium bicarbonate
- Salt cake
- sodium nitrate
It later aids in oxidizing iron and speeding up melting.
Sodium nitrate
It is sourced from limestone and burnt lime from dolomite (the latter introduces MgO into the batch).
Lime
General formula of feldspars
R2OAl2O36SiO2
It is cheap, pure, and fusible.
Feldspars
It is composed entirely of glass-forming oxides.
Feldspars
True or False: Alumina content lowers the melting point and retard devitrification.
True
It supplies glass with NaO2 and boric oxide.
Borax
It has high fluxing power, lowers expansion coefficient, and increases chemical durability.
Borax
It is said to remove troublesome scum from tank furnaces and acts as oxidizing agent by removing impurities such as iron oxide and convert it to a form that can be easily removed from the molten glass.
Salt cake
crushed glass from imperfect articles, trim, and other waste.
Cullet
It facilitates melting and utilizes waste and can constitute 10% to 80% of the charge.
Cullet
Used for their ability to withstand high temperatures without melting or deforming.
Refractory Blocks
Four major phases/Methods for manufacturing of glasses (4)
- Melting
- Shaping/Forming
- Annealing
- Finishing
Two types of furnace used in melting.
- Pot Furnace
- Tank Furnace
Used for small-scale production of special glasses (optical and art glass by casting process)
Pot Furnace
Pots are crucibles made of selected clay and platinum, latter is chosen to minimize product contamination and ensure furnace durability and longevity.
Pot Furnace
Capacity is 2 tons or less
Pot Furnace
Capacity is 1350 tons
Tank Furnace
Dimensions of tank furnace
Approximately 3891.5 m
Batch materials charged at one end, built from refractory block.
Tank Furnace
Glass forms a pool in the hearth of the furnace.
Tank Furnace
Refined glass exits from the opposite end through continuous operation.
Tank Furnace
Ways for shaping or molding (2)
- Machine
- Hand molding
In a short time, glass changes shape from viscous liquid to clear solid.
Shaping or molding
Considerations when shaping or molding (3)
- Flow of heat
- Stability of metals
- Clearance of bearings
Most common types of machine-shaped glass (8)
- Window glass
- plate glass
- float glass
- wired and patterned glass
- blown glass
- light bulbs
- television tubes
- glass tubing
It is done to reduce strain.
Annealing
Designed heated chamber which rate of cooling can be controlled.
Annealing lehr
It includes cleaning, grinding, polishing, cutting, sandblasting, enameling, grading, and gaging.
Finishing
PFD of float glass making
Crushing > Mixing > Melting > Shaping or Molding > Annealing > Finishing