Paper Flashcards
(101 cards)
1
Q
What is the basic molecular composition of paper? what else is composed of this?
A
cellulose
cotton, wood
2
Q
What is cellulose?
A
linear chain carbohydrate, repeated beta-1,4 glucan units linked
3
Q
how are cellulose units linked?
A
covalent bonds (from OH on C4 and C1)
4
Q
The chemical structure of paper makes it difficult to: __
A
process in solution or as a melt
5
Q
What is a polymer?
A
large molecule made of small repeating units
6
Q
What is a monomer?
A
molecule that combines with others (identical or different) through covalent bonds to form polymer
7
Q
Examples of synthetic polymers:
A
rubber, nylon, polyethylene
8
Q
True/False: all polymers are manufactured
A
False; many biological molecules are natural polymers
9
Q
What are examples of natural polymers?
A
cellulose, starch, chitin, protins
10
Q
What differentiates different polymers?
A
monomer units
molecular weight
branches/linking structure
11
Q
What are sources of cellulose to make paper? (3)
A
Wood
Cotton/linen/straw (minor sources)
Recycled paper
12
Q
What are the 2 main types of wood for paper? What are their characteristics?
A
Hardwood (short fibre, smooth paper, good printing, low strength)
Softwood (long fibre, strong, good fold strength, poor printing)
13
Q
what trees are hardwood trees?
A
maple, birch
14
Q
What trees are softwood trees?
A
pine, spruce (evergreens)
15
Q
The main insoluble fibres in wood: (3)
A
lignin
hemicellulose
cellulose
16
Q
The cellulose microfibrils in wood are contained within the _______, between the ____ and _____
A
primary wall
middle lamella, plasma membrane
17
Q
The process of cellulose extraction is known as:
A
pulping
18
Q
What are the main methods of pulping? (2)
A
mechanical
chemical
19
Q
Characteristics of mechanical pulping: (5)
A
cheaper (yield 95%) break down fibres lignin remains weak, poor color easily discolored
20
Q
Mechanically pulped paper is usually used for:
A
newsprint, egg cartons
21
Q
Characteristics of Chemical pulping: (5)
A
expensive (yield 40-50%) low fibre breakdown lignin dissolved strong pulp (varies depending on chemical types/process)
22
Q
True/False: Mechanical pulping yields high quality paper
A
False
23
Q
For a very cheap wrapping paper, what type of pulping could be used?
A
mechanical (cheap, low quality/strength paper)
24
Q
True/False: Chemically pulped paper will have lignin remaining
A
False; will be dissolved
25
True/False: Mechanically pulped paper has most fibres broken
True
26
What is "furnishing?"
cooking wood with chemicals to separate cellulose
27
What are common processes for paper furnishing?
Kraft (sulfate) process
| Sulfite process
28
True/False: Sulfite process yields stronger paper
False (Kraft is stronger)
29
What is the origin of the name "kraft process"
Kraft is German for 'strong'
30
What are the chemicals used in sulfate vs sulfite processes?
Sulfate: Alkaline (Na carbonate, NaOH, Na2S)
Sulfite: Acid (sulfurous acid, Na sulfite)
31
How does sulfite vs sulfate process affect final appearance of paper?
sulfite: white paper
sulfate: brown paper
32
True/False: Kraft process paper is easier to bleach
False; sulfite process paper is easier to bleach/refine
33
What are the stages the wood goes through in the kraft process?
wood chips -> cooked pulp -> washed pulp -> bleached pulp
34
What is the Kraft liquor cycle?
white liquor is used to cook/wash chips -> yields black liquor after cooking
black liquor is evaporated, burned, makeup chemicals added -> green liquor
Green liquor is causticized
yields new white liquor to continue cycle
35
What is white liquor composed of?
NaOH
| Na2S
36
What is the composition of black liquor?
alkali lignin
hydrolysis salts
sulphonation products
37
What is the composition of green liquor?
Na2CO3
| Na2S
38
What is the purpose of caustisizing?
convert Na2CO3 to NaOH (using CaO)
39
Where is CaO needed, and supplied from in the Kraft Liquor cycle?
needed for caustisizing step
supplied from lime kiln
40
True/False: wood chips are cooked and washed with Green liquor
False; with white liquor
41
What are 3 examples of pulp treatments?
bleaching
mechanical beating
acid treating
42
What is the purpose of pulp treatments? (2)
improve paper-forming process
| improve paper performance
43
What causes a dark pulp color?
residual lignin
44
What chemicals are used in bleaching?
Cl2, NaOH, ClO2, H2O2 (in sequence)
45
Purpose of bleaching?
remove residual lignin to improve physical & optical properties (whiteness/brightness)
46
Disadvantage of bleaching:
weakens fibres -> reduced sheet strength
47
What machines can be used for mechanical beating?
Hollander beater
| Conical (Jordan) refiner
48
how does low amount of mechanical beating affect paper properties?
absorbs well
resists tears
low burst strength
low tensile strength
49
How does high amounts of mechanical beating affect paper properties?
high burst strength
high tensile strength
low tear resistance
50
The quality of having low tear resistance is known as _____
glassine
51
True/False: the greater the beating time, the greater the tensile strength
True
52
True/False: If beating time is too long, it will lead to a large reduction in burst strength
True
53
What happens to tear strength as beating time increases?
decreases
54
True/False: a paper with low mechanical beating will have poor absorbance but good strength
False; good absorbance, low strength
55
Beating will increase ___ and ____ resistance
water
| grease
56
glassine paper qualities:
low tear resistence
high burst/tensile strength
water and grease resistant
57
What is 'sizing,' and why is it added?
starch and alum
improve water resistance, printability, adhesiveness
58
What is a sulfuric acid bath used for?
Parchment
| matt fibres, improve grease resistance
59
paper qualities that can be modified with chemical additives: (4)
color
opacity
stiffness
waterproofing
60
An additive used to increase opacity and brightness: ____
Titania (TiO2)
61
What is CMC used for as a paper additive?
increase water resistance
62
What additive gives paper a greasy/soapy feel?
Talc (MgO/SiO2)
| increases high finish
63
What additives help to fill and coat paper?
```
china clay (kaolin)
limestone CaCO3
```
64
What additives help increase water resistance?
CMC
| Polyethylene
65
What is the purpose of adding guar gum to paper?
increase dry strength
66
the basic process of a fourdrinier machine:
furnished pulp placed on wire mesh
mesh vibrates -> fibres align, water drains
water squeezed out by rollers
passed through heated drums
smoothed with calendar rolls
collect in paper roll
67
The draining mesh section of a fourdriner machine is known as the ___ ___, while the heated drums are known as the ___ ___
wet end
dry end
68
The paper at the dry end is rolled with ___ ____ in order to _______
calendar rolls
smooth the surface
69
Paper can be ____ to improve the surface
coated
70
Clay coating on paper can achieve what?
fills gaps
improves whiteness
improve printability
71
What is the significance of the grain direction in paper? (3)
tear: easier along direction of grain
stiffness: greater along grain
fold endurance: greater across grain
72
True/False: paper vs paperboard are made from different materials
False; both made from matted cellulose fibres
73
What is the main difference between paper vs paperboard?
thickness
<0.3mm is paper
>0.3mm is paperboard
74
What is the difference in applications of paper vs paperboard?
paper: used for primary packaging, bags or labels
paperboard: secondary packaging
75
Paper is tested at specific conditions of ______. Why?
23C, RH 50%
will pick up humidity and increase in size when wet
76
Kraft paper has what characteristics, and what uses?
brown, unbleached
grocery bags, wrapping
77
sulfite paper is lighter and weaker than ____ paper, but has high _____. What is it used for?
kraft paper
print quality
biscuit/candy bags
78
The paper usually used for bags and labels:
Bleached paper (white)
79
What paper is used for butter? What qualities does it have?
parchment
translucent, gelatinized surface (grease resistant)
80
____ paper is very smooth and water/grease proof. It is used for _____
glassine
deli meat, cheese
81
True/False: cellophane is a type of paper
True
82
What qualities does cellophane have
transparent
| brittle
83
What are major types of paper bags?
```
flat & square
flat or square
automatic
satchel bottom
window
preformed pouches
```
84
What is 'chipboard?'
type of paperboard, low quality (recycled); not for contact with food
85
types of lined chipboard:
SWL (single white lined)
| DWL (double white lined)
86
What is CCNB?
clay coated news back (paperboard)
87
What is SUS?
solid unbleached sulfate (paperboard) - 100% chemical pulp
88
What is SBS?
solid bleached sulfate (paperboard) - 100% bleached chemical pulp
89
What are common paperboard packages? (4)
```
folding cartons (tubes, trays, baskets)
liquid containers (tetrapaks, juice box)
fibre cans (spiral or convolute wound - pillsbury tin)
carded displays (ex: gum packs)
```
90
What is a 'blank' in carton making?
cut shape that will become carton
91
What is a 'score' in carton making?
creases on blank to fold to form carton
92
What is 'cut score' in carton making?
cut partly through sheet of paperboard
93
creasing a paperboard forms a ____, which when folded will form a ____ on the (inside/outside) of the fold
valley
| ridge; inside
94
True/False: the paperboard is folded towards the same direction it was creased
False; folded away from crease (creased valley/indent is on outside)
95
When are cartons most breakable? Why?
when freshly cut and scored
over time, fibres set in folds, make breaking harder
96
What is the order in which dimensions are described for cartons?
1. length
2. width
3. depth
97
2 end styles for paperboard tube carton?
reverse tuck
| straight tuck
98
What features are tested for paper and paperboard? (7)
```
basis weight (wt per unit area)
thickness
folding endurance (bend stiffness, durability)
puncture resistance
burst strength
tensile strength
water vapor permeability
```
99
How is puncture strength tested?
triangular pyramid puncture
100
advantages of paper/paperboard: (6)
```
cheap
versatile
easy to make
printable
treatable
renewable/biodegradable
```
101
Disadvantages of paper/paperboard:
consumption of resources
waste
chemical byproducts
