Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Y1 Materials and Manufacturing - Sem 2 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Polymer materials consist of

A

long chain molecules usually with a back bone of carbon atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What bonding do we see in polymers?

A

covalent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Polymers can ……… that enables it to twist into a variety of positions

A

rotate around the axis of the C-C bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What changes the polymers chain structure and properties?

A

Side groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Mer unit is

A

the basic structure that the chain is formed from

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Condensation polymerisation usually

A

combines two different monomers into the chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Condensation polymerisation produces a small

A

molecule by-product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which polymer; only secondary bonds between the polymer chains%

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which polymer; many cavalent bonds (cross-links) between the polymer chains%

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Which polymer; rubbery materials can be thermoset or thermoplastic versions%

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Thermoplastic polymers are

A

polymers that consist of many molecules that are linked to each other ONLY by secondary bonds and entanglement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

A stronger thermoplastic polymer means what for the glass transition temp?

A

higher glass transition temp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The absence of primary bonds in thermoplastic polymers means that the chains can

A

slide past each other when loaded at a high temp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

By heating a thermoplastic polymer what does it turn into? What can we do with this?

A

Viscous liquid - which can be formed and moulded easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Differences in the depiction of an amorphous and semi-crystalline thermoplastic?

A

Amorphous - scribbled mess, intertwined and messy

Semi-crystalline - regular neat chains snaking around each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Through a polymerisation process, what can we not determine without controlling the process parameters?

A

The average chain length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The degree of polymerisation DP represents the

A

average number of mer units in the chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

A high DP means

A

the chains are longer therefore a high molecular weight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

A low DP means

A

the chains are shorter therefore a low molecular weight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

If a polymer is linear, what does it mean?

A

Close packed and neat linear chain structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Branched polymer, what does it mean?

A

the polymers during polymerisation become branched and cannot pack so closely together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Copolymers consist of

A

chains with two different mer units that can be regularly or randomly arranged or formed into blocks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Chains of different mer units can also be ——-

A

attached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

In a thermoplastic, how do they usually form a region of regular crystalline structure?

A

When the long chains fold and align

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

The driving force for the thermoplastic forming a region of regular structure is%

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Cooling rate in a thermoplastic determined the

A

level of crystallinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Fast cooling =

Slow cooling =

A

low crystallinity

high crystallinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Spherulites are formed when

A

lamellae start from from a central nucleation site and grow into spherical arrangements

29
Q

What affects the way in which the chain molecules pack to for lamellae?

A

Arrangement of the side groups

30
Q

Large side groups can make —– —— difficult and also reduces —– ——

A

crystal formation, chain mobility

31
Q

What is the term used to refer to a polymer with side groups all attached on one side of the C-C bonds?

A

Isotactic

32
Q

What is the term used to refer to a polymer with side groups attached on both sides, in alternating orders, of the C-C bonds?

A

Syndiotactic

33
Q

What is the term used to refer to a polymer with side groups attached on both sides of the C-C bonds with no specific order?

A

Atactic

34
Q

Higher crystallinity leads to:

A
  • Higher melting point
  • Increased solvent resistance
  • Increased stiffness
  • Reduced permeation of gases
  • Light scattering - get opaque materials if crystals are large
35
Q

Cooling an amorphous polymer, what are the characteristics observed?

A
  • No distinct solidification or crystallisation
  • Reformation of secondary bonds which limits motion of the motion of the particles — material turns into a rubbery material
  • Once it has cooled right down below Tg, insufficient energy to break the secondary bonds — material turns brittle and glassy
36
Q

Cooling a semi-crystalline polymer, what are the characteristics observed?

A
  • Shows intermediate behaviour
  • Change in volume at Tm as some of the chains for lamellae
  • Amorphous regions between lamellae cease movement, around Tg it becomes glassy
37
Q

Tg =

A

glass transition temperature

38
Q

Tm =

A

melting temperature

39
Q

Yield strength for a polymer is defined at what point?

A

When the neck begins to form

40
Q

When tensile testing a thermoplastic, what sort of feature does it initially display?

A

Proportional stress/strain relationship

41
Q

As a polymer strip is put under a tensile test and is stretched, what happens to the fibres?

A

Initially they are jumbled up but as the force is applied and the neck begins to form, the fibres all line up

42
Q

Viscoelastic materials

A

exhibit elastic behaviour when loaded over a short time but will flow. appear viscous when loaded over a longer time

43
Q

For many polymers, creep can occur at

A

room temperature or just above

44
Q

Creep is

A

the deformation or stretching of polymers subjected to a constant stress, over a period of time

45
Q

The deflection temp of a polymer indicates the ….

A

likelihood of creep

46
Q

Mer unit of polyethylene

A

H H
| |
-C- C-
| |
H H

47
Q

Polyethylene is typically used in

A

bags, electrical equipment, bottles

48
Q

Few pros of polyethylene

A
  • Low cost
  • Tough
  • Flexible
  • Corrosion resistant
49
Q

Mer unit of polypropylene

A

H H
| |
-C-C-
| |
H CH3

50
Q

Few pros of polypropylene

A
  • Low cost
  • Tough
  • flexible
  • Stronger than PE and better at high temp
51
Q

Polypropylene is typically used in

A

packaging, pipes and fittings, chairs

52
Q

Mer unit of Polytetrafluoroethylene

A

F F
| |
-C-C-
| |
F F

53
Q

Typical uses for Polytetrafluoroethylene

A

gaskets, inert lab equipment, electrical insulation

54
Q

Pro of Polytetrafluoroethylene

A

low stick due to low surface energy

55
Q

Nylon is known for the chemical name of

A

polyamide

56
Q

Thermoset polymers ——– – —– once formed into a structure

A

cannot be reformed

57
Q

Thermoset polymers are better than thermoplastics due to the reasons that they have a ….. and …..

A

good chemical resistance and higher operating temperature

58
Q

3 examples of thermoset polymers

A
  • Phenol-formaldehyde
  • Urea-formaldehyde
  • Melamine-formaldehyde
59
Q

As thermoset polymers are linked together with —– —— ——, the material does not show many variations in properties …….

A

strong covalent bonds, with temperature as thermoplastics do

60
Q

Two things oberved about thermoset polymers that are not oberved in thermoplastics

A
  • Very little softening occurs when raised to a high temperature, too high and the material begins to degrade
  • Tg is usually high, won’t “flow” but will become more compliant
61
Q

What are the characteristics to an elastomer when put under a straining force?

A
  • All deformation is elastic - no plastic deformation
  • Bonds stretched as more force is applied to the material
  • Sudden failure is seen
62
Q

Thermoset elastometers have only a few….

A

cross links joining the polymer chains together

63
Q

Silicones have —– —— but made up of Si-O

A

long chains

64
Q

Polymer additives are

A

additional materials which are mixed into a polymer to change its mechanical properties, such as strength and wearability etc…

65
Q

Filler additives are those added to

A

improve;
- tensile and compressive strength
- abrasion resisitance
- toughness
- dimensional stability

66
Q

Plasticiser additives are

A

small molecules added to a polymer which obstruct the secondary bonding between molecules

67
Q

Stabiliser additives are added to

A

prevent deterioration of the polymer in service due to exposure to light and atmosphere

68
Q

Stabiliser additives can reduce the chance of

A
  • colour change
  • deterioration of mechanical properties
  • cracking
  • surface crazing
  • UV bond breakage
69
Q

——- ——- are added to polymers to reduce the flammability of the organic materials

A

Flame retardants

Y1 Materials and Manufacturing - Sem 2 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions