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Polymers > Exam 1 Review > Flashcards

Exam 1 Review Flashcards

1
Q

What’s in a mer?

A

A mer contains the basic repeating structure that defines the primary properties of the polymer

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2
Q

What does ethylene vs. polyethylene look like?

A
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3
Q

What was the first commercial synthetic polymer?

A

1860’s - 1909
Parkesine– Bakelite
Derivative of natural cellulose

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4
Q

What is the difference between cellulose and nitrocellulose?

A

Cellulose
1. Linear chain
2. Degrades before melting
3. Insoluble

Nitrocellulose
1. Soluble
2. Melt-formable
3. NO2

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5
Q

What are 5 cellulose derivatives?

A
  1. Parkesine
  2. Bakelite
  3. Celluloid
  4. Cellophane
  5. Rayon
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6
Q

What are three ways to draw polyethylene?

A

Assume carbon’s 4 bonding sites are filled with hydrogen unless otherwise specified

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7
Q

How do you represent a double bond in shorthand?

A

A double line

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8
Q

How do you draw poly(ethylene glycol)

A
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9
Q

How many covalent bonds does oxygen need to reach stability?

A

only 2. it has 6 valence electrons

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10
Q

What does a methyl group look like? amino group? styrene?

A
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11
Q

What is a functional group?

A

A group of atoms that join the backbone of a repeating unit that further define the properties of the resulting polymer.

They contribute to the properties of the resulting materal

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12
Q

What is the effect of branches of crystallinity?

A

Linear polymers will crystallize more freely than short-chain branched polymers

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13
Q

What are four properties of linear polymers?

A
  1. chains stack easily into a crystal structure
  2. packing (and therefore density) can be increased
  3. higher crystallinity: stronger and stiffer
  4. lower crystallinity: flexible and often transparent
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14
Q

What is lamella?

A

a stack of folded polymer chains

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15
Q

What are two examples of products made from linear polymers (HDPE & LDPE)?

A

HDPE: milk carton
LDPE: plastic bag

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16
Q

What are two important characteristics of crystallinity in polymers?

A
  1. Fully crystalline polymer is practically impossible
  2. polymers are typically comprised of amorphous and crystalline regions
17
Q

What does a drawing of HDPE vs. LDPE look like?

A
18
Q

Which polymer type, linear of branched, has what density?

A

Linear: high density
Branched: low density

19
Q

What are two characteristics of branched homopolymers?

A
  1. Branches are composed of the same units as backbone
  2. Higher branching reduces crystallinity and density
20
Q

What does branching affect?

A

Short vs. long chain branching affects
1. density (short chain- higher density)
2. other macro properties

21
Q

What leads to the formation of networks?

A
  1. Branching
  2. Non-covalent/ionic bonding. Such as hydrogen bonds or van der walls forces
22
Q

What functionality is needed to form networks?

A

> 2

23
Q

What is functionality?

A

The number of bonds that a repeating unit can form within a polymer with other repeating units

24
Q

What is cross-linking? (3 facts)

A
  1. When linear chains are connected via covalent or ionic bonds
  2. Differs from networked resins, which leverages functionality>2
  3. comprised of a different compound
25
Q

What is an example of crosslinking?

A

Vulcanization

Natural rubber (polyisoprene) is a linear polymer. When sulfur is added, chains can bond together.

26
Q

What is stereoisomerism? What is it described in terms of?

A

Stereoisomerism: when atoms have the same molecular formula but different placement in 3D

It’s described in terms of “tacticity”

27
Q

What are the characteristics of a thermoplastic?

A
  1. Weak intermolecular forces between polymer chains
  2. Can be repeatedly become plastic (soft/pliable/moldable) upon heating and rigid upon cooling
28
Q

What are the characteristics of a thermoset polymer?

A
  1. Strong covalent bonds between chemical chains
  2. Irreversibly harden upon heating
29
Q

How is a polymer determined to be thermoplastic or thermoset?

A

Chain structure and functionality

30
Q

Describe polyethylene (PE)

A

PE
1. simplest and most common polymer
2. uses vary according to molecular weight & related characteristics

31
Q

Describe poly(ethyleneterephthalate)

A

PET or PETE
1. most common member of thermoplastic polyester family
2. Often produced as a fiber or thermoformed
3. terephthalate group + ethylene group

32
Q

Describe polypropylene

A

PP
1. General used in PE applications requiring a bit more ruggedness
2. Packaging is most common use, as are fibrous applications (rope)

33
Q

Describe polystyrene

A

PS
1. Great for foamed applications, also molding and vacuforming
2. This is because it has a log Tg but moderately high Tm allowing it to retain shape well during heat processing

34
Q

Describe poly(vinyl chloride)

A

PVC
1. A strong and rigid commodity thermoplastic
2. Can be made more flexible with addition of plasticizers

35
Q
A

Polymers (3 decks)

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