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FDSC 400 > PAPER > Flashcards

PAPER Flashcards

1
Q

what is the major component of paper?

A

cellulose

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2
Q

describe the structure of cellulose

A

linear polymer with repeating b-1,4-glucan units covalently linked between the 1 and 4C

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3
Q

it is difficult to process cellulose in _____ or as a _____

A

solution (hard to dissolve); melt

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4
Q

large molecules made up of many repeating units

A

polymer

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5
Q

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

A

monomer

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6
Q

is polyethylene a polymer or monomer?

A

polymer

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7
Q

ethylene is the monomer for what polymer?

A

polyethylene

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8
Q

how can polymers be categorized?

A

synthetic, natural

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9
Q

what are some synthetic polymers?

A
  • rubber
  • nylon
  • polyethylene
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10
Q

what are some natural polymers?

A
  • cellulose
  • starch
  • chitin
  • proteins
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11
Q

what are some sources of cellulose?

A
  • wood
  • cotton
  • linen
  • straw
  • recycled paper
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12
Q

distinguish between the papers from hardwood and softwood

A

hardwood: short fibers, smooth paper, good printing, low strength

softwood long fibers, strong paper, good fold strength, poor printing

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13
Q

what is the major raw material for cellulose? why?

A

wood; we have a lot of forest and is more price efficient

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14
Q

what happens to cellulose fibers as you recycle them?

A

the fibers get cut shorter and shorter resulting in decreased strength of paper

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15
Q

what exists between cellulose fibers to hold them together?

A
  • lignin

- hemicellulose

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16
Q

true or false: lignin and hemicellulose are components of paper

A

false

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17
Q

what holds the fibers of paper together?

A

its physical network structure - not covalent bonds

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18
Q

why is paper so easy to break?

A

physical interactions are weaker than chemical ones, and paper is connected by a physical network

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19
Q

why is paper so permeable?

A

there’s many holes in the physical network

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20
Q

why is paper so flammable?

A

the cellulose structure becomes unstable at around 200C (even in the absence of oxygen)

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21
Q

describe the process of early chinese paper making

A
  • obtain raw material (wood, bamboo) and boil with alkaline (Calcium oxide CaO) for several days
  • sieve the fibers and form into sheets
  • stick wet sheets into furnace to dry out
22
Q

what’s responsible for the off-colors in paper that has yet to be bleached?

A

lignin residues

23
Q

when do you add additives to paper?

A

after bleaching, while the cellulose are still dispersed in water (wet)

24
Q

what two machines make paper with different mechanisms? what do they both do?

A
  • cylinder
  • fourdrinier

deposit fibers onto surface and send off to be dried

25
Q

when do you add a coating to paper?

A

after it pops out of the dryers

26
Q

what is the first step of papermaking?

A

pulping - extracting cellulose

27
Q

what two methods of pulping are there?

A

mechanical, chemical

28
Q

characteristics of mechanical pulping

A
  • friction (rotating stone) breaks down wood chips to get its fiber
  • cheaper (1 kg wood yields 0.95 kg fiber)
  • breaks down fibers
  • doesn’t remove lignin
  • weak paper with poor color
  • prone to discoloration
  • used for newspaper, egg cartons
29
Q

characteristics of chemical pulping

A
  • expensive (yields 40-50% pulp, and need to purchase the chemicals)
  • low fiber break-down
  • lignin is dissolved
  • strong to very strong pulp
  • strength and properties vary with the type of chemical process
30
Q

what is furnishing?

A

part of chemical pulp processing

31
Q

what are the Kraft and sulfite processes?

A

common chemical pulp processes

32
Q

describe the sulphAte pulp properties

A

aka Kraft

  • uses alkaline (sodium carbonate, NaOH, sodium sulfide)
  • brown paper
  • higher sheet strength
  • harder to bleach
33
Q

describe the sulfite pulp properties

A
  • uses acid (sulfurous acid, sodium sulfite)
  • white
  • lower sheet strength
  • easier to bleach and refine
34
Q

which chemical pulping method is more popular?

A

Kraft

35
Q

describe the kraft process

A

“cook” chips in alkaline to get pulp, wash, bleach

36
Q

what is the Kraft Liquor cycle?

A

a way to recycle chemicals used

  • cook & wash
  • evaporate and burn
  • caustizing

part of the caustizing step includes the addition of calcium oxide, which ultimately converts the Na2CO3 in green liquor to NaOH

this NaOH can then be reused in the cooking process

37
Q

what are the components of green liquor?

A
  • Na2CO3

- Na2S

38
Q

what converts CaCO3 to CaO?

A

heat

39
Q

under what treatments can pulp go?

A
  • bleaching
  • mechanical beating
  • acid treating
40
Q

what do we use to bleach?

A
  • Cl2 (chlorine)
  • NaOH
  • ClO2 (chlorine peroxide)
  • H2O2 (hydrogen peroxide)
    in this sequence
41
Q

what does bleaching accomplish?

A
  • whitens by removing residual lignin
  • weakens fibers
  • reduces sheet strength
42
Q

what does mechanical beating do?

A
  • length of beating changes burst, tensile, and tear strength
  • improves water and grease resistance
43
Q

a low amount of mechanical beating does what regarding absorption, tear, burst, and tensile strengths?

A
  • absorbs well
  • resists tear
  • low burst and tensile strength
44
Q

a high amount of mechanical beating does what regarding burst/tensile strength and tear resistance?

A
  • burst/tensile strength: higher

- tear resistance: lower

45
Q

what additives are incorporated into paper to improve water resistance, printability, and adhesive properties?

A

sizing (starch, alum)

46
Q

what is a chemical pulping method other than kraft and sulfite? it makes parchment

A
  • sulfuric acid bath
47
Q

additives can be added to improve…

A
  • color
  • opacity (titanium dioxide TiO2)
  • stiffness
  • waterproofing
48
Q

increases opacity and brightens paper

A

Titania (TiO2)

49
Q

increases water resistance

A
  • CMC

- polyethylene

50
Q

Adds greasy or soapy feel; increases high finish

A

Talc (MgO/SiO2)

51
Q

fills and coats

A
  • China clay (kaolin)

- limestone (CaCO3)

52
Q

increases dry strength

A

guar gum

FDSC 400 (5 decks)

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