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Materials Science > Chapter 14 (Polymers) > Flashcards

Chapter 14 (Polymers) Flashcards

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1
Q

What are plastics and Elastomers made from?

A

polymeric materials

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2
Q

what are the benefits of COMMERCIAL polymers (3)?

A
  • lightweight
  • corrosion-resistant
  • good maleability
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3
Q

what are the benefits of ENGINEERING polymers? (3)

A
  • improved strength

- better properties at high temps

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4
Q

what are most polymers made of?

A

hydrocarbons (H&C)

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5
Q

what is a saturated carbon?

A

a carbon bonded to 4 other atoms

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6
Q

what can be said about double and triple bonds?

A

they are reactive and likely to form new bonds

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7
Q

Name a double bond and describe the carbon configuration

A

Ethylene or ethene. Each C has 4 bonds, but only 3 atoms bound to it due to the double bond

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8
Q

name a triple bond and describe the carbon configuration

A

acetylene or ethyne. Each carbon has 4 bonds but only 2 atoms bonded to it due to the triple bond

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9
Q

How many and what type of bond does a carbon molecule want to form

A

4 covalent bonds

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10
Q

If a double or triple bond is formed, what kind of molecules do we have?

A

unsaturated hydrocarbon molecules

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11
Q

how are other groups formed (excluding H)

A

by arranging varying proportions of hydrocarbons and end groups

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12
Q

what are “mers” (monomers)

A

the basic building unit. These are combined to form a polymer

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13
Q

What is Isomerism, and give an example

A

when 2 compound with the same chemical formula can have different structures, ex: C8H18 can make n-ocatne and isooctane

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14
Q

what is the process of the joining of monomers to form polymers

A

polymerization

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15
Q

What is the polymer of the ethene monomer?

A

Polyethylene

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16
Q

What is the molar mass?

A

the mass of one mole of polymer chains

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17
Q

If a chain is made up of 10000 repeat units and the molar mass is 30, then what is the relative molecular mass

A

10000 * 30=300,000 g/mol

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18
Q

what is the molecular weight?

A

the mass of a mole of chains, the longer the chain, the greater the weight

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19
Q

what is the relationship between Tensile strength and Molecular Weight

A

As Molecular weight increases, so does Tensile strength. Because the longer chains are generally more entangled therefore stronger

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20
Q

What is the percent crystallinity?

A

the percent of a material that is crystalline

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21
Q

As % crystallinity increase what also increases?

A

Tensile strength and E(yungs)

22
Q

If we want to increase the %crystallinity, what process can we use?

A

annealing.

23
Q

what is the degree of polymerization?

A

the average number of repeat units per chain

24
Q

Which types of bonds/side groups restrict rotation

A

double bonds restrict rotation and bulky side groups as well

25
Q

what are linear polymers

A

mers joined end to end to form a long chain

26
Q

what are branched polymers, and what effect do these have?

A

side branches connected to the main chain. this tends to reduce density. Note: this can also occur in linear polymers

27
Q

what are cross-linked polymers and give an example

A

adjacent linear chains have occasional covalent crosslinking. eg rubbers

28
Q

what are network polymers

A

trifuctional mers (3 covalent bonds) form 3-D networks

29
Q

what is tacticity?

A

stereoregularity of the chain (repitition)

30
Q

list the 3 types of tacticity and describe them

A
  1. Isotactic: all R groups are on the SAME side of the chain
  2. Syndiotactic: R groups are on ALTERNATING sides of the chain
  3. Atactic: R groups have random positioning
31
Q

What is the difference between Cis and Trans isomerism

A

Cis: bulky groups are on the same side of the chain
Trans: bulky groups are on the opposite sides of the chain

32
Q

List the properties of Thermoplastics: (3)

A
  1. they soften upon heating
  2. can be formed and shaped by viscous flow
  3. Retain shape during cooling and this process can be repeated
33
Q

What atoms are found of the side groups of thermoplastics and what is the chain made of

A

H, O, N. Consists of long carbon chains

34
Q

How are the carbon atoms bonded to chain.

A

COVALENTLY -»chains are very strong

35
Q

How are Thermosets formed?

A

the are formed/shaped then cured or set by chemical reaction

36
Q

can thermosetting plastics be reshaped

A

no, their formation is permanent

37
Q

what is their chain composed of?

A

a NETWORK of COVALENTLY bonded carbon atoms

38
Q

what other sidegroups are present in thermosets?

A

H, O, N

39
Q

what happens when elastomers (rubbers) are loaded

A

very large elastic deformations, can be recovered

40
Q

List some properties of Plastics as engineering materials? (8)

A
  1. very low density
  2. excellent formability
  3. low cost
  4. noise reduction
  5. corrosion resistant
  6. low friction
  7. electrically insulating
  8. can have tailored properties
41
Q

List the types of Copolymers (6) and briefly describe them

A
  1. Homopolymers: chains of the same repeating unit(AAAA-)
  2. Copolymers: 2 or more chemically different repeating units (A&B)
  3. Random: Random arrangement of different mers
  4. Alternating: Ordered: unlike groups attract each other ie And B alternate
  5. Block: Ordered: like groups attract each other ie large groups of A alternate with large groups of B
  6. Graft: Grafts of one type appear on another chain, ie cahins of B attached to A backbone
42
Q

what is a copolymer?

A

when 2 or more polymers are polymerized together

43
Q

Which type of polymer is most crystalline

A

thermoplastics

44
Q

if we cool a thermoplastic what will be the result?

A

can form and amorphous structure or become semi-crystalline

45
Q

what must be the case for a polymer to be crystalline

A

it must haveChain folded structure

46
Q

How can single crystals be formed in polymers

A

if we have slow and careful growth

47
Q

How can we create a spherulite crystal form, and what structure would it have

A

through fast growth which forms lamellar strucutre(layered strucutres)

48
Q

what is a maltese cross?

A

the joining of polarizers

49
Q

what is the relationship between strength and % crystallinity?

A

higher %cryst. Higher strength

50
Q

can atactic polymers crystallize

A

never, they soften at a low temp

51
Q

can Isotactic polymers crystallize

A

yes, partially crystalline. their melting temp is much greater

Materials Science (13 decks)

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