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Material Science Y1 > Oxygen and Nitrogen Based Polymers 1 > Flashcards

Oxygen and Nitrogen Based Polymers 1 Flashcards

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1
Q

what does the 6 represent in Nylon 6?

A

the number of carbons between amide groups

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2
Q

Structural properties of Nylon:

A

+ High tensile strength
+ High elasticity, toughness and abrasion strength
- Can be hydrolysed at high temps
- stabilisers are needed to increase weather resistance
- water can act as a plasticiser

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3
Q

Thermal properties of Nylon:

A

+ Tough and flexible at low temps

+ Good mechanical properties to ~150 degrees

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4
Q

Applications of Nylon

A
  • carpets, rope
  • tool casings, ski boots
  • cable insulation
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5
Q

why does Nylon tend to have a high tensile strength

A

Hydrogen bonds between amide groups of parallel chains, the more amide groups the stronger

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6
Q

What is a polyaramid?

A

A polymer containing benzene amide groups in the chain backbone

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7
Q

properties of polyaramid:

A
  • High strength, toughness and thermal stability
  • Water and acids affect the material properties
  • Decompose at very high temps
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8
Q

Applications of Polyaramids:

A
  • Ballistic protection
  • tyres
  • cut resistant gloves or materials
  • concrete reinforcement
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9
Q

Properties of Polycarbonates:

A
  • Very high Tg
  • Hard
  • Transparent
  • strong and tough
  • consistent properties between -30 and 120 degrees
  • made from dangerous precursors
  • high Tmelting and low crystallinity
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10
Q

Applications of Polycarbonates:

A
  • Safety glazing, CDs DVDs and Bottles
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11
Q

PET properties:

A
  • High Tg ~70 degrees, high Tm ~265 degrees,

- rigid and strong and a good electrical insulator

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12
Q

PET applications:

A
  • Bottles
  • Oven wear, thermoformed food packages
  • automotive and engineering moulds
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13
Q

PLA properties:

A

like PET but no aromatic group so lower resistance to high temps and degredation

  • Sustainable as its from a renewable source, and biodegradable
  • difficult to recycle
  • Tg ~60-65 degrees
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14
Q

why can PLA be easily degraded?

A

it has an ester group so water can attack and degrade it easily

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15
Q

PLA applications:

A
  • Particles for drug delivery

- Sweet wrappers, bottles, fruit containers

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16
Q

Which polymers have aromatic groups?

A
  • Polyaramids

- PC and PET

17
Q

how does an aromatic group change properties?

A
  • Aromatic groups have a high resistance to high temperatures so high Tg and Tmelting and resistant to degredation, so are not biodegradable
18
Q

PCL properties:

A
  • no aromatic group so is biodegradable

- hydrophobic and semicrystalline polymer

19
Q

applications of PCL:

A
  • Many biomedical uses

- nanofibers, knitted tensiles

20
Q

what is PVC?

A

a polymer chain of the monomer chloroethene

21
Q

how is PVC made?

A

free radical polymerisation

22
Q

is PVC atactic, sydiotactic or isotactic?

A

always atactic, but can sometimes be syndiotactic which gives a low level of crystallinity

23
Q

what 2 types of PVC do you get?

A

Unplasticised PVC and Plasticised PVC

24
Q

Properites of uPVC:

A
  • Rigid due to no plasticisers
  • Tg ~80 degrees
  • fire retardant because of chlorine
25
Q

Properties of pPVC:

A
  • Plasticised so flexible
  • fire retardant because of chlorine
  • lower Tg than uPVC because of plasticisers
26
Q

how can PVC be modified (3):

A

1) Stabiliser which allow processing without degredation
2) Lubricants which assist flow of the melt in machinery
3) Plasticisers which reduce Tg, increase flexibility/toughness

27
Q

How do Plasticisers work?

A
  • Plasticisers space PVC chains apart by sitting between them, increasing the distance between polar Cl groups reducing the strength of the dipole dipole bonds.
28
Q

what is a good plasticiser?

A

Phthalates are good, most substances ending in -ates

29
Q

applications of uPVC:

A

pipes, bottles, cladding

30
Q

applications of pPVC:

A

medical tubing, toys, tape, cable insulation

31
Q

what are the 2 main different Fluoropolymers?

A

PTFE and PVDF

32
Q

structure of PTFE:

A

polytetrafluoroethylene, 2 carbons and 4 fluorine monomer

33
Q

what properties does the Fluoro group add?

A
  • C-F bond is extremely strong so inert chains
  • also very stiff and strong due to strength of bond
  • High melting point~335 and Tg
  • Large F group means it forms a helical structure
  • non-flammable and good chemical resistance
  • good electrical insulators
  • expensive and hard to process (hard to create the strong bond)
34
Q

how do you process PTFE?

A

1- cold press the polymer into the desired shape

2- then sinter above the Tm at ~380 degrees

35
Q

structure of PVDF:

A

Polyvinvylidenfluoride, 2 carbons with 2 fluorines on each carbon and 2 hydrogens on the other

36
Q

How does PVDF compare to PTFE?

A
  • More easily processed due to less fluorines

- still very inert but less so that PTFE

37
Q

Applications of Fluoropolymer:

A
  • corrosive chemical plants, high voltage casing, aerospace equipment

Material Science Y1 (4 decks)

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