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Food Packaging > Paper > Flashcards

Paper Flashcards

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1
Q

What is the basic molecular composition of paper? what else is composed of this?

A

cellulose

cotton, wood

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2
Q

What is cellulose?

A

linear chain carbohydrate, repeated beta-1,4 glucan units linked

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3
Q

how are cellulose units linked?

A

covalent bonds (from OH on C4 and C1)

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4
Q

The chemical structure of paper makes it difficult to: __

A

process in solution or as a melt

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5
Q

What is a polymer?

A

large molecule made of small repeating units

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6
Q

What is a monomer?

A

molecule that combines with others (identical or different) through covalent bonds to form polymer

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7
Q

Examples of synthetic polymers:

A

rubber, nylon, polyethylene

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8
Q

True/False: all polymers are manufactured

A

False; many biological molecules are natural polymers

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9
Q

What are examples of natural polymers?

A

cellulose, starch, chitin, protins

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10
Q

What differentiates different polymers?

A

monomer units
molecular weight
branches/linking structure

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11
Q

What are sources of cellulose to make paper? (3)

A

Wood
Cotton/linen/straw (minor sources)
Recycled paper

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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)

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13
Q

what trees are hardwood trees?

A

maple, birch

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14
Q

What trees are softwood trees?

A

pine, spruce (evergreens)

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15
Q

The main insoluble fibres in wood: (3)

A

lignin
hemicellulose
cellulose

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16
Q

The cellulose microfibrils in wood are contained within the _______, between the ____ and _____

A

primary wall

middle lamella, plasma membrane

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17
Q

The process of cellulose extraction is known as:

A

pulping

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18
Q

What are the main methods of pulping? (2)

A

mechanical

chemical

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19
Q

Characteristics of mechanical pulping: (5)

A 
cheaper (yield 95%)
break down fibres
lignin remains
weak, poor color
easily discolored
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20
Q

Mechanically pulped paper is usually used for:

A

newsprint, egg cartons

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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)
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22
Q

True/False: Mechanical pulping yields high quality paper

A

False

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23
Q

For a very cheap wrapping paper, what type of pulping could be used?

A

mechanical (cheap, low quality/strength paper)

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24
Q

True/False: Chemically pulped paper will have lignin remaining

A

False; will be dissolved

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25
Q

True/False: Mechanically pulped paper has most fibres broken

A

True

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26
Q

What is “furnishing?”

A

cooking wood with chemicals to separate cellulose

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27
Q

What are common processes for paper furnishing?

A

Kraft (sulfate) process

Sulfite process

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28
Q

True/False: Sulfite process yields stronger paper

A

False (Kraft is stronger)

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29
Q

What is the origin of the name “kraft process”

A

Kraft is German for ‘strong’

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30
Q

What are the chemicals used in sulfate vs sulfite processes?

A

Sulfate: Alkaline (Na carbonate, NaOH, Na2S)

Sulfite: Acid (sulfurous acid, Na sulfite)

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31
Q

How does sulfite vs sulfate process affect final appearance of paper?

A

sulfite: white paper
sulfate: brown paper

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32
Q

True/False: Kraft process paper is easier to bleach

A

False; sulfite process paper is easier to bleach/refine

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33
Q

What are the stages the wood goes through in the kraft process?

A

wood chips -> cooked pulp -> washed pulp -> bleached pulp

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34
Q

What is the Kraft liquor cycle?

A

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

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35
Q

What is white liquor composed of?

A

NaOH

Na2S

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36
Q

What is the composition of black liquor?

A

alkali lignin
hydrolysis salts
sulphonation products

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37
Q

What is the composition of green liquor?

A

Na2CO3

Na2S

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38
Q

What is the purpose of caustisizing?

A

convert Na2CO3 to NaOH (using CaO)

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39
Q

Where is CaO needed, and supplied from in the Kraft Liquor cycle?

A

needed for caustisizing step

supplied from lime kiln

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40
Q

True/False: wood chips are cooked and washed with Green liquor

A

False; with white liquor

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41
Q

What are 3 examples of pulp treatments?

A

bleaching
mechanical beating
acid treating

42
Q

What is the purpose of pulp treatments? (2)

A

improve paper-forming process

improve paper performance

43
Q

What causes a dark pulp color?

A

residual lignin

44
Q

What chemicals are used in bleaching?

A

Cl2, NaOH, ClO2, H2O2 (in sequence)

45
Q

Purpose of bleaching?

A

remove residual lignin to improve physical & optical properties (whiteness/brightness)

46
Q

Disadvantage of bleaching:

A

weakens fibres -> reduced sheet strength

47
Q

What machines can be used for mechanical beating?

A

Hollander beater

Conical (Jordan) refiner

48
Q

how does low amount of mechanical beating affect paper properties?

A

absorbs well
resists tears

low burst strength
low tensile strength

49
Q

How does high amounts of mechanical beating affect paper properties?

A

high burst strength
high tensile strength

low tear resistance

50
Q

The quality of having low tear resistance is known as _____

A

glassine

51
Q

True/False: the greater the beating time, the greater the tensile strength

A

True

52
Q

True/False: If beating time is too long, it will lead to a large reduction in burst strength

A

True

53
Q

What happens to tear strength as beating time increases?

A

decreases

54
Q

True/False: a paper with low mechanical beating will have poor absorbance but good strength

A

False; good absorbance, low strength

55
Q

Beating will increase ___ and ____ resistance

A

water

grease

56
Q

glassine paper qualities:

A

low tear resistence
high burst/tensile strength
water and grease resistant

57
Q

What is ‘sizing,’ and why is it added?

A

starch and alum

improve water resistance, printability, adhesiveness

58
Q

What is a sulfuric acid bath used for?

A

Parchment

matt fibres, improve grease resistance

59
Q

paper qualities that can be modified with chemical additives: (4)

A

color
opacity
stiffness
waterproofing

60
Q

An additive used to increase opacity and brightness: ____

A

Titania (TiO2)

61
Q

What is CMC used for as a paper additive?

A

increase water resistance

62
Q

What additive gives paper a greasy/soapy feel?

A

Talc (MgO/SiO2)

increases high finish

63
Q

What additives help to fill and coat paper?

A 
china clay (kaolin)
limestone CaCO3
64
Q

What additives help increase water resistance?

A

CMC

Polyethylene

65
Q

What is the purpose of adding guar gum to paper?

A

increase dry strength

66
Q

the basic process of a fourdrinier machine:

A

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
Q

The draining mesh section of a fourdriner machine is known as the ___ ___, while the heated drums are known as the ___ ___

A

wet end

dry end

68
Q

The paper at the dry end is rolled with ___ ____ in order to _______

A

calendar rolls

smooth the surface

69
Q

Paper can be ____ to improve the surface

A

coated

70
Q

Clay coating on paper can achieve what?

A

fills gaps
improves whiteness
improve printability

71
Q

What is the significance of the grain direction in paper? (3)

A

tear: easier along direction of grain
stiffness: greater along grain

fold endurance: greater across grain

72
Q

True/False: paper vs paperboard are made from different materials

A

False; both made from matted cellulose fibres

73
Q

What is the main difference between paper vs paperboard?

A

thickness
<0.3mm is paper
>0.3mm is paperboard

74
Q

What is the difference in applications of paper vs paperboard?

A

paper: used for primary packaging, bags or labels
paperboard: secondary packaging

75
Q

Paper is tested at specific conditions of ______. Why?

A

23C, RH 50%

will pick up humidity and increase in size when wet

76
Q

Kraft paper has what characteristics, and what uses?

A

brown, unbleached

grocery bags, wrapping

77
Q

sulfite paper is lighter and weaker than ____ paper, but has high _____. What is it used for?

A

kraft paper

print quality

biscuit/candy bags

78
Q

The paper usually used for bags and labels:

A

Bleached paper (white)

79
Q

What paper is used for butter? What qualities does it have?

A

parchment

translucent, gelatinized surface (grease resistant)

80
Q

____ paper is very smooth and water/grease proof. It is used for _____

A

glassine

deli meat, cheese

81
Q

True/False: cellophane is a type of paper

A

True

82
Q

What qualities does cellophane have

A

transparent

brittle

83
Q

What are major types of paper bags?

A 
flat &amp; square
flat or square
automatic
satchel bottom
window
preformed pouches
84
Q

What is ‘chipboard?’

A

type of paperboard, low quality (recycled); not for contact with food

85
Q

types of lined chipboard:

A

SWL (single white lined)

DWL (double white lined)

86
Q

What is CCNB?

A

clay coated news back (paperboard)

87
Q

What is SUS?

A

solid unbleached sulfate (paperboard) - 100% chemical pulp

88
Q

What is SBS?

A

solid bleached sulfate (paperboard) - 100% bleached chemical pulp

89
Q

What are common paperboard packages? (4)

A 
folding cartons (tubes, trays, baskets)
liquid containers (tetrapaks, juice box)
fibre cans (spiral or convolute wound - pillsbury tin)
carded displays (ex: gum packs)
90
Q

What is a ‘blank’ in carton making?

A

cut shape that will become carton

91
Q

What is a ‘score’ in carton making?

A

creases on blank to fold to form carton

92
Q

What is ‘cut score’ in carton making?

A

cut partly through sheet of paperboard

93
Q

creasing a paperboard forms a ____, which when folded will form a ____ on the (inside/outside) of the fold

A

valley

ridge; inside

94
Q

True/False: the paperboard is folded towards the same direction it was creased

A

False; folded away from crease (creased valley/indent is on outside)

95
Q

When are cartons most breakable? Why?

A

when freshly cut and scored

over time, fibres set in folds, make breaking harder

96
Q

What is the order in which dimensions are described for cartons?

A
  1. length
  2. width
  3. depth
97
Q

2 end styles for paperboard tube carton?

A

reverse tuck

straight tuck

98
Q

What features are tested for paper and paperboard? (7)

A 
basis weight (wt per unit area)
thickness
folding endurance (bend stiffness, durability)
puncture resistance
burst strength
tensile strength
water vapor permeability
99
Q

How is puncture strength tested?

A

triangular pyramid puncture

100
Q

advantages of paper/paperboard: (6)

A 
cheap
versatile
easy to make
printable
treatable
renewable/biodegradable
101
Q

Disadvantages of paper/paperboard:

A

consumption of resources
waste
chemical byproducts

Food Packaging (11 decks)

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