Glass Flashcards
(112 cards)
1
Q
What is the major component of glass?
A
silicon (silicon dioxide)
2
Q
Where can silicon be obtained?
A
quartz, sand, cristobalite, feldspar, kaolinite
3
Q
What is the structure of glass?
A
amorphous (no crystallizing)
4
Q
True/False: Glass is an organic product
A
False; inorganic product
5
Q
Characteristics of silica crystals: (4)
A
very high melt temp.
high toughness
low transparency
poor inertness
6
Q
The basis of the glass-making process:
A
change inorganic ingredients from crystalline to amorphous state, at temperature above 1450-1500C
7
Q
What visual differences can be seen in crystalline vs amorphous structures? Why?
A
crystalline: not transparent (crystals reflect light)
amorphous: transparent (light can pass through)
8
Q
Molecular units in glass have a ____ arrangement, but sufficient ____ to produce mechanical rigidity
A
disordered
cohesion
9
Q
Basic formula of glass:
A
soda-limestone
10
Q
What are the various specific ingredients of glass?
A
silica (SiO2) limestone (CaCO3 -> CaO) soda ash (Na2CO3 -> Na2O) alumina (Al2O3) Cullet (recycled glass)
11
Q
What is the largest chemical ingredient of glass?
A
silica sand (SiO2)
12
Q
What is the role of soda ash in glass?
A
network modifier
fluxes, enhances melting of silica
13
Q
What is the role of limestone in glass?
A
stabilizer
increase chem resistance, increase refractive index
14
Q
Why is cullet added to glass?
A
to reduce cost/energy
15
Q
Boron oxide is added to what types of glass?
A
heat stable glass
16
Q
Can glass be used to store alkaline material? Why?
A
No; will react slowly with glass and degrade over time
17
Q
What is used to dissolve glass?
A
HF (only acid that can dissolve silica)
18
Q
What are metal oxides used for in glass?
A
colorants, bleaching
19
Q
What are various stabilizers added to glass?
A
Ca carbonate
Mg carbonate
Ba carbonate
20
Q
What is added to glass as a fining agent?
A
Na sulfate
21
Q
Sodium and potassium carbonate are added to glass for what reason?
A
fluxes
22
Q
What is added to achieve amber glass?
A
carbon & sulfur compounds
23
Q
What is added for blue glass?
A
cobalt oxide
24
Q
What is added for green glass?
A
ferrous sulfate, chromic oxide
25
What is added for yellow glass?
ferric oxide, antimony oxide
26
What is added for blue-green glass?
cobalt oxide and chromium oxide
27
What is added for opal glass?
calcium oxide
28
Why does the addition of different metal oxides give various colors?
different metal cations have different ionic refractions
29
basic steps of glass production:
raw materials -> mixing -> melting -> forming -> glass
30
Glass is made in ____ processing
batch
31
the heating step for glass production takes place in a ____, heated to a temp of ____.
furnace
| 1500C (2700F)
32
What processes happen during the melting of glass? (5)
```
decarbonation
dehydration
solid-state reactions
formation of low-melting eutectics
dissolutions
```
33
The temperature is raised during glass melting in order to ___ ___
release gas
34
In order to work/form the glass, what needs to occur?
glass needs to be cooled slightly (otherwise will stick)
35
After melting, if the temperature is too hot, the glass will _____. If it is too cold, it _____
too hot => sticks
| too cold => won't flow
36
3 process/zones of the glass furnace?
1. melting & sand dissolution
2. primary fining
3. secondary fining (refining)
37
steps in the glass furnace:
1. batch input
2. batch melting => rough melt
3. sand grain dissolution => seedy melt
4. fining => clear melt
5. refine/condition => conditioned melt
38
what step in the glass furnace yields the 'clear melt?'
fining
39
How does the melting process compare to the fining process?
melting: fast (1hr), need a lot of energy
fining: longer time (24 hr), lower energy input
40
the 2 routes for melting and sand dissolution:
carbonate route
| silicate route
41
What requires a higher temp? the Carbonate or silicate route for melting?
silicate (700-860C)
42
What is the temperature range for the carbonate route?
550-850C
| reaction enhanced >820C
43
what is the purpose of fluxing agents
1. formation of early melt phases
2. decrease surface tension
3. increase heat conductivity
44
About ____% of the mass of normal soda-lime silica bath is transferred into volatile ____
14-20%
CO2
45
1 kg of normal batch will generate ____ L of gas at room temp
100
46
True/False: finely crushed cullet will release gas later than coarse cullet
False; fine cullet will have early gas release
47
What is glass 'fining?'
eliminate gases through heating -> bubbles (rise to surface)
48
Describe the process of glass fining
high temperature, dissolved gases diffuse from melt into bubbles (agglomeration and growth) -> ascend to surface
49
What gases are produced by fining?
O2, SO2
50
The greater the glass melt ____, the slower the bubble ascension
viscosity
51
lower ___, and lower ___ will increase speed of bubble ascension. Which has the greater impact?
```
glass melt density
bubble radius (bigger impact; squared)
```
52
At (higher/lower) temperatures, the melt will have lower viscosity
higher
53
What reaches the surface first? bubbles in a melt at 1400C, or bubbles in a melt at 1500C?
1500C
54
What reaches the surface first? bubbles of 300um or 600um?
300um
55
What is 'refining' of glass, what does it achieve?
controlled cooling of melt
dissolution of small bubbles remaining
(reverses fining reaction)
56
Bottles are formed automatically in the ___ ___ machine
individual section
57
How does a individual section machine function?
molten glass 'gobs' sheared off
| bottles/jars formed in parison moulds (blow & blow method or press & blow method)
58
The main 2 functions of a individual section machine:
shape
| remove heat
59
2 main processes for shaping:
blow and blow
| press and blow
60
process of blow & blow (7 steps)
1. gob dropped into parison mould
2. sealed, settle-blow (air from top push glass into finish/neck)
3. counter-blow (air from bottom push glass up into mould and shapes it)
4. parison removed from mould, rotate 180
5. transfer into blow mould for finishing
6. blow air from top to expand/press against mould
7. opened, bottle removed, passed to annealing lehr
61
process of press and blow (6 steps)
1. gob dropped in mould
2. sealed, plunger moves up; glass forms around it
3. parison removed from mold, rotate 180
4. transferred to blow (finishing) mould
5. air from top expands glass, press against mould
6. opened, bottle removed, passed to annealing lehr
62
How is the parison formed in blow & blow vs press & blow?
blow & blow: form both finish and rest of parison by air
press & blow: form finish/rough parison with plunger; complete with air
63
Does B&B or P&B have greater heat removal?
P&B has greater heat removal
64
True/False; P&B glassmaking creates more uniform thickness
True
65
True/False: B&B is faster than P&B
False; B&B is slower
66
What types of bottles are made in B&B vs. P&B?
B&B: narrow neck bottles
P&B: narrow neck or wide mouth
67
The neck of a bottle is known as the ____
finish
68
the sloping part of a bottle between the body and finish is called the ____
shoulder
69
What is the purpose of coating glass?
improve quality, machinability, durability, strength, appearance, functionality
70
True/False: Glass coatings are designed to be permanent
False;
| can be permanent, semipermanent, or nonpermanent
71
Examples of permanent glass coatings:
tin oxide
| PE
72
Examples of semipermanent glass coating:
PE, silicone
73
nonpermanent glass coatings:
PVA, stearate
74
When are glass coatings added?
Before the lehr (hot end) - 2 steps
After the lehr (cold end) - 1 step
75
What is the Shat-R-Kote coating? What properties does it give to glass?
Ionomer resin (ethylene/methacrylic acid copolymer)
```
acid/solvent resistant
transparent
high tensile strength (shatterproof)
no label adhesive needed
90% UV block, antioxidant
```
76
What is 'annealing?'
reheating glass to soften (550-700C), remove internal stresses caused by heat, cool slowly
77
What is the measurmenet unit of viscosity?
poises
78
What is the viscosity for the working point, softening point, and annealing point of glass?
working point: 10^4
softening point: 10^7.6
annealing point: 10^13
79
How is the softening point of glass determined?
glass fibre 1mm stretches under its own weight (1mm/min)
80
What inspection quality control technologies are used for glass?
electro-optical, radio frequency, visual tests
| detect dangerous and ugly defects -> glass used as cullet
81
What are some machine tests used for glass inspection (7)
bottle spacer (avoid contact between bottles)
squeeze tester (presses between discs
bore gauger finish (measure inside/outside diameter)
check detector (candles problem areas)
wall thickness detector (scan wall for faults)
hydraulic pressure tester (gauge internal pressure)
visual check (final check)
82
Some qualities of glass that should be inspected: (5)
```
internal pressure breakage
vertical load strength
impact strength
resistance to abrasion & scratching
thermal shock breakage
```
83
True/False: thickness is the most important feature of glass when considering vertical load strength
False; shoulder design (bottle shape) is more important factor than glass thickness
84
types of impacts:
bottle striking stationary object
| stationary bottle hits moving object
85
___ ____ glass is more resistant to internal pressure, but it has poor ________.
thick walled glass
| thermal shock resistance
86
What shape of glass has better resistance to thermal shock?
round/spherical shape
87
(Bigger/smaller) glasses have greater resistance to thermal shock
smaller
88
The higher the weight/capacity ratio of bottles, the (higher/lower) the limiting sudden temperature drop
lower
89
classifications of glass defects:
critical (hazardous or unusable; cracks or overpress)
major (reduced usability; sunken centre, oval finish)
minor (loss of acceptibility; heeltap, seeds)
90
What is a 'heeltap?' what are 'seeds?'
heeltap: heavy (thicker) glass on the side
seeds: small bubbles in glass
91
What markings are seen on the bottom of glass bottles?
1. identification of mould (plant, company mark, year)
| 2. stippling to minimize shock in lehr
92
specifications for glass containers should include:
1. description of container finish
| 2. dimensions (capacity, ht, diameter, wt, tolerances)
93
Glassware finishes must be compatible with _____
the closure type
94
Examples of finishes:
sprinkler top, shallow CT, Tall CT, pour-out CT, crown, cork, roll-on, biological, handle
95
Finishes are designated with a ____ system from the ______
2 number
GPI (glass packaging institute)
(matches finish with closure)
96
what does the 2 number system for glass finishes describe?
1st number: millimeter diameter across inside cap's opening/bottle threads
2nd number: thread style
97
The various thread styles for closures:
400: continuous
500: twist off
600: crown
2000: vacuum
1600: roll on
98
The different 'dimensions' of the finish
```
T: outside diameter of the thread (spiral ridges that allow screw caps)
E: outside diameter of neck
I: inner diameter of neck
S: top of finish to top of first thread
H: height of neck finish
```
99
What does "T" dimension of finishes determine?
mate between bottle and closure
100
What does "S" dimension of finishes determine? (2)
orientation of closure to bottle
| amount of thread engagement between bottle & cap
101
How do you determine thread depth?
difference between "T" and "E"
102
Why do specifications require a minimum "I" dimension for finishes?
allow filling tubes to fit
| plugs and seal proper fit
103
True/False: melting and remoulding of glass can be repeated indefinitely without loss of properties
True
104
The presence of ___ and ____ in glass will hugely increase the heat resistance
boron oxides, aluminum oxides
105
Glass has the lowest coefficient of ___ ___ of any packaging material
coefficient of thermal expansion (6-8*10^(-6) /C)
106
What has a greater impact on reducing the stress resistance of glass, the composition or the weight/thickness?
weight and thickness
107
True/False: Glass can have cracks and flaws, even if it is not visible
True; superficial defects lead to stress amplification
108
What are the optical properties of glass? (3)
transparent in visible wavelengths
transparent to microwaves
very low UV transmission coefficients (absorb in UV range)
109
Glass can't be penetrated by: ______ (4)
moisture
gases
odors
microbes
110
Can glass react with food?
No; inert (does not react or migrate)
111
Advantages of glass as packaging: (10)
```
good barrier properties
inert
fast filling
can use heat processing
reusable, recyclable
resealable
variety of shapes, colors
adds value (perception)
rigid (stacking)
Printable (or labels)
```
112
disadvantages of glass as packaging: (6)
```
high weight/volume ratio
low strength/weight ratio
friability (tend to chip)
susceptible to imperfections
safety (when broken)
energy intensive production
```
