Glass Industry Flashcards
Definition of glass, physically
a rigid, undercooled liquid having no definite melting point and a sufficiently high viscosity (greater than 1012 Pa.s) to prevent crystallization.
Definition of glass, chemically
combination of nonvolatile inorganic oxides formed by the decomposition and fusion of alkali and alkaline earth compounds, sand, and other glass constituents, resulting in a product with a random atomic structure.
Glass has many uses because of its
transparency, high resistance to chemical attack, effectiveness as an electrical insulator, and ability to contain a vacuum.
Ancient Phoenician merchants discovered glass while
cooking a metal in a vessel place accidentally upon a mass of trona at the seashore
were making sham jewels of glass which were often of fine workmanship and marked beauty.
As early as 6000 or 5000 B.C the Egyptians
invented the hand-blown window glass cylinder.
A monk from the twelfth century
Glass work in the United States were founded in
1608 at Jamestown, Virginia, and in 1639 at Salem, Massachusetts
Major ingredients of glass
Sand
Lime
Soda ash
The most important factors in making glass are
viscosity of molten oxides and the relation between this viscosity and composition
commercial glasses fall into several classes
- Fused silica (vitreous silica)
- Alkali silicates
- Soda-lime glass
- Lead glass
- Borosilicate glass
- Special glasses
- Glass fibers
Made by the high-temperature pyrolysis of silicon tetrachloride or by fusion of quartz or pure sand.
Fused silica
is widely consumed as an adhesive for paper in the manufacture of corrugated paper boxes.
Silicates of soda solution also known as water (soluble) glass
• Sand and soda ash are simply melted together, and the products designated sodium silicates
• It aided the glass technologist in understanding the behavior of more complicated systems
Alkali silicates
• constitutes 95% of all glass manufactured
• Used for containers of all kinds, flat glass, automobile, and other windows, tumblers, and tableware.
Soda-lime glass
• obtained by substituting lead oxide for calcium oxide in the glass melt
• Because of their high index of refraction and dispersion, these glasses are extremely useful in optical work
Lead glass
• usually contains about 10 to 20% B2O3, 80 to 87% Silica and less than 10% Na2O.
• has a low expansion coefficient, superior resistance to shock, excellent chemical stability, and high electrical resistance.
Borosilicate glass
the laboratory glassware made from borosilicate glass is sold under the tradename
Pyrex
Colored and coated, opal, translucent, safety, optical, photochromic glasses, and glass ceramics are ______. All of these have varying compositions depending upon the final product desired
Special glasses
• produced from special glass compositions that are resistant to weather conditions.
• The very large surface area of the fibers makes them vulnerable to attack by moisture in the air.
• This glass is low in silica, about 55%, and low in alkali
Glass fibers
Raw materials of glass
- Sand
- Soda
- Feldspar
- Borax
- Salt cake
- Cullet
- Refractory blocks
- Decolorizer
manufacturing sequences
• Transportation of raw materials to the plant
• Sizing of some raw materials
• Conveying, weighing, and mixing raw materials, and feeding them into the glass furnace
• Burning of the fuel to secure the temperature needed for glass formation
• Reactions in the furnace to form glass
• Saving of heat by regeneration or recuperation
• Shaping of glass products
• Annealing of glass products
• Finishing of glass products
manufacturing procedures may be divided into four major phases
Melting
Shaping or forming
Annealing
Finishing
Glass furnaces may be classified as either
pot or tank furnaces
For special glasses like optical glass. Raw materials are melted in _____ made of ceramic material capacities varying from 1-2 tons and is used for small production batches
pot furnace
Molten glass is obtained by melting the raw materials in 1350-1400 ton capacity regenerative _______ and can be used in continuous processes.
tank furnace
types of machine molding
• Fourcault process : window glass
• Colburn process : window glass
• Continuous automatic process : plate glass
• Float process : float glass
• Glass blowing : bottles, light bulbs, tubing
an example of a “vertical draw” process, in that the glass is drawn gainst gravity in an upward direction
Fourcault process
Fourcault process is a method of manufacturing flat glass. First developed
in Belgium by Émile Fourcault (1862–1919) during the early 1900s
is a heated chamber in which the rate of cooling can be controlled
The lehr or annealing oven
the production of sheet glass using began with an iron rod as “bait” immersed lengthwise in a shallow tank of molten glass.
Colburn process
used to make high-quality, flat glass for the construction and automotive industry
Float process
used to make thin-walled hollow glass items, such as bottles and glass containers.
Glass blowing
two primary methods of making glass containers:
blow and blow method for narrow-neck containers only, and the press and blow method used for jars and tapered narrow-neck containers.
When glass cools from the forming range to room temperature , thermal stresses develop that adversely affect strength properties. _______ is done to eliminate this stress.
Annealing
All types of annealed glass must undergo certain finishing operations, which are simple and important. These include:
• Cleaning.
• Grinding.
• Polishing.
• Cutting.
• Sandblasting.
• Grading etc
MANUFACTURE OF SPECIAL GLASSES
FUSED SILICA GLASS
HIGH-SILICA GLASS
COLORED AND COATED GLASSES
SAFETY GLASS
FOTOFORM
PHOTOCHROMIC SILICATE GLASSES
GLASS-CERAMIC
FIBERGLASS
vitreous silica, may be made by fusing pure silica, but such products are usually blebby and difficult to produce in transparent form.
FUSED SILICA GLASS
known as Vycor. This method of glass manufacture furnishes a product that can be heated to a cherry red and then plunged into ice water without any ill effects.
HIGH-SILICA GLASS
Colored glass may be one of three types:
a) Color is produced by the absorption of certain light frequencies by agents in solution in the glass.
b) Color is produced by colloidal particles precipitated within an originally colorless glass by heat treatment.
c) Color is produced by microscopic or larger particles which may be colored themselves, such as selenium reds (SeO2) used in traffic lights, lantern globes, etc., or the particles may be colorless, producing opalescent glass.
made by depositing transparent metallic films on the surface of clear or colored glass.
Coated glass
clear when molten but become opalescent as the glass is worked into form
Opal or translucent glasses
produced by growing nonmetallic crystals from nucleated silver particles developed from an original clear glass containing silver.
Opal glass
Safety glass may be grouped into two general classes
Laminated safety glass
Heat-strengthened (or tempered) or case-hardened safety glass
most widely used in this country, consists of two sheets of thin plate glass, each of which is about 3 mm thick, with a sheet of nonbrittle plastic material between.
Laminated safety glass
• very strong and tough. It is used for doors and windows of automobiles and for pipe.
• It possesses high internal stresses and, if the surface is broken, shatters into many pieces
Heat-strengthened (or tempered) or case-hardened safety glass
a photosensitive glass that is essentially a lithium silicate modified by potassium oxide and aluminum oxide and contains traces of cerium and silver compounds as photosensitive ingredients.
Fotoform
supplement the just presented Fotoform glass
Photochromic silicate glasses
Photochromic silicate glasses possess the following unusual properties:
• optical darkening in light from ultraviolet through the visible spectrum;
• optical bleaching, or fading in the dark;
• thermal bleaching at higher temperatures.
material that is melted and formed as glass, and then converted largely to a crystalline ceramic by processes of controlled devitrification.
GLASS-CERAMIC
although not a new product, owes its enhanced usefulness to its extreme fineness (often about 10nm but it may down to 5 nm or less). A special glass, low in silica, is used for the production of fibers.
FIBERGLASS
Itisalso known as recycled glass
Cullet
