Module 4 Flashcards
is an inorganic, noncrystalline, brittle solid that is formed by cooling from a liquid state
Glass
It shows no discontinuous change in properties at any temperature, but becomes more rigid when its temperature decreases and less rigid when its temperature increases.
Glass
occurs at a level of stress approximately equal to yield stress.
The proportional limit
causes the material to be permanently deformed
Stress greater than the yield stress value
When tiny crystals form in a repeating orderly fashion in a material, the material is said to be
crystalline or to have “crystalline regions”
Is glass amorphous or crystalline?
Amorphous
Glass is sometimes is reffered to as a
supercooled liquid
heat from a volcano can melt sand to form a natural glass called
obsidian.
lightning strikes onto a sand dune or beach can melt sand to form a natural glass called
fulgurite
There are two such natural heat sources that occur in nature:
volcanoes and lightning
wrote that the process of glass making was discovered when Phoenician mariners used pieces of natron to support cooking pots over a campfire on the beach.
Pliny, Roman historian
a mixture of soda ash and sodium bicarbonate
Natron
Glass beads were used in Syria in
12,000 BC
The Egyptians had glass jewelry in
700 BC
The Egyptians made glass bottles by winding strands of glass onto baked clay forms in
3000BC
Blowpipes were first used around ______ to form glass objects
300 BC
The _______ greatly improved the ability of artisans to produce glass objects.
blowpipe
The Romans produced flat glass in
200 BC
Glass manufacturing began at ____ in ____.
Jamestown, in the Virginia colony, in 1608
Use of manual glass container manufacturing machines began in the
1800s
worked for the Libby Company, invented the first automated bottle-making machine in 1903.
Michael Owens
If a ______ is added to the mix, the glass will be colored.
colorant
Three Selected Types of Glass
Glass Made from Pure Silica
Glass Made from Soda and Silica
Container (Packaging) Glass
Characteristics of Pure Silica Glass
• Inexpensive raw material
• Excellent durability
• High energy requirements to melt the mix
• Hard to fine (remove bubbles)
• Hard to form
• Expensive to process
The only significant application is for the manufacture of mirrors and lenses for telescopes and other optical equipment.
Glass Made from Pure Silica
This type of glass is used in the chemical industry because it is resistant to attack by many chemicals.
Glass Made from Soda and Silica
is made of a mixture of several materials, including silica, soda, calcium carbonate (calcia), aluminum oxide, and other materials
Container glass
which are added to improve the durability of the glass, also increase the viscosity of the melt, making the container manufacturing process more difficult and more expensive.
Aluminum oxide and calcium carbonate
The _________ is the part of the plant where the ingredients are mixed in the proper quantities to be added to the glass furnace
batch house
The batch house is located at the
input end of the glass furnace
The _____ are usually supported on heavy frames above a large conveyor that feeds the hopper.
silos
The ingredients are thoroughly mixed together and then dumped into a _____, which dumps the mix into the furnace
hopper
The glass furnace consists of a number of sections:
melter, bridgewall, throat, refiner, and one or more forehearths
The _____ is the largest section of the glass furnace.
melter
The _____ form the end of the melter opposite the input end.
bridgewall and throat
floating mix of impurities is typically referred to as
slag
The _____ is the section on the downstream side of the bridgewall
refiner
The _____ is the section on the downstream side of the bridgewall
refiner
Small bubbles float to the surface and are removed in a step known as
fining
are ceramic-lined troughs like bathtubs that convey the glass from the refiner to the glass container forming machines
Forehearths
are shaped to influence the quantity of glass that flows into different parts of the container
Gobs
As the molten glass leaves the spout, a gob is cut off by the
gob shears
Containers are formed in
IS (individual section) machines
preliminary form of the container
Parison
There are two basic approaches to manufacturing containers:
1) press and blow molding or 2) blow and blow molding
to manufacture containers with wide necks, jars and cups.
Press and Blow Molding
A wide-neck jar is usually defined as having a finish larger than
43 mm in diameter
Annealing is done in a large oven called a
lehr
is applied at the hot end (the front end) of the annealing lehr
A bonding agent (usually tin or titanium tetrachloride)
At the cold end (the back end) of the lehr, what is applied?
a friction-reducing agent (or a coating) is applied. Coatings that are applied include polyethylene, waxes, and silicones.
Following are some of the defects that can cause rejection of a container:
• Dimensions that are out of tolerance
1. Thread height
2. Finish diameter
3. Sealing ring at the top of the finish
4. Diameter of the body
5. Bottom
• Chips or cracks
• Birdswings (glass bridge across the interior of the container)
• Bubbles
• Color variation
Containers that reach the end of the manufacturing process are packaged for delivery to the customer. There are two approaches that can be used:
(1) bulk handling, and (2) reshippers
The glass manufacturing process includes two steps that are specifically intended to improve the strength of the containers:
annealing and coating.
is the process of changing from a vitreous structure to a crystalline structure as the glass cools.
Devitrification
The bridgewall extends partways down from the surface, leaving an open area, called the _____, under the wall.
throat
Design and Manufacturing Factors That Affect Container Strength
• Distribution of glass throughout the container, including thickness at various points and the distribution pattern of the glass into specific areas, such as corners
• Container shape, such as the sharpness of radii, and so on.
• Surface condition, such as scratches on the surface of the glass. Tiny scratches act as stress concentrators, substantially reducing the strength of the glass.
• The type of load. As discussed previously, glass is very strong in compression, but often fails under tension.
Ways to Improve the Strength of Glass
• Anneal containers in a lehr to relieve internal stresses in the container.
• Limit surface damage.
• Build compressive stresses into the material (although this is not done much with packaging glasses and will not be discussed here).
• Change the package design (change radii, take out corners, increase wall thickness, change the distribution of glass in the mold, etc).
