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Materials Science > Chapter 14 (Polymers) > Flashcards

Chapter 14 (Polymers) Flashcards

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
what are linear polymers
mers joined end to end to form a long chain
26
what are branched polymers, and what effect do these have?
side branches connected to the main chain. this tends to reduce density. Note: this can also occur in linear polymers
27
what are cross-linked polymers and give an example
adjacent linear chains have occasional covalent crosslinking. eg rubbers
28
what are network polymers
trifuctional mers (3 covalent bonds) form 3-D networks
29
what is tacticity?
stereoregularity of the chain (repitition)
30
list the 3 types of tacticity and describe them
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
What is the difference between Cis and Trans isomerism
Cis: bulky groups are on the same side of the chain Trans: bulky groups are on the opposite sides of the chain
32
List the properties of Thermoplastics: (3)
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
What atoms are found of the side groups of thermoplastics and what is the chain made of
H, O, N. Consists of long carbon chains
34
How are the carbon atoms bonded to chain.
COVALENTLY ->>chains are very strong
35
How are Thermosets formed?
the are formed/shaped then cured or set by chemical reaction
36
can thermosetting plastics be reshaped
no, their formation is permanent
37
what is their chain composed of?
a NETWORK of COVALENTLY bonded carbon atoms
38
what other sidegroups are present in thermosets?
H, O, N
39
what happens when elastomers (rubbers) are loaded
very large elastic deformations, can be recovered
40
List some properties of Plastics as engineering materials? (8)
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
List the types of Copolymers (6) and briefly describe them
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
what is a copolymer?
when 2 or more polymers are polymerized together
43
Which type of polymer is most crystalline
thermoplastics
44
if we cool a thermoplastic what will be the result?
can form and amorphous structure or become semi-crystalline
45
what must be the case for a polymer to be crystalline
it must haveChain folded structure
46
How can single crystals be formed in polymers
if we have slow and careful growth
47
How can we create a spherulite crystal form, and what structure would it have
through fast growth which forms lamellar strucutre(layered strucutres)
48
what is a maltese cross?
the joining of polarizers
49
what is the relationship between strength and % crystallinity?
higher %cryst. Higher strength
50
can atactic polymers crystallize
never, they soften at a low temp
51
can Isotactic polymers crystallize
yes, partially crystalline. their melting temp is much greater

Materials Science (13 decks)

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