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Materials > Plastics > Flashcards

Plastics Flashcards

1
Q

What is the fundamental building block of plastics?

A

Carbon

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2
Q

What are synthetic plastics made from?

A

Crude oil

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3
Q

What is the single repeated unit that make up a plastic?

A

a monomer

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4
Q

What process happens to monomers to transform them to polymers?

A

Polymerisation

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5
Q

How are plastic properties altered?

A

Additives added to the polymers

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6
Q

name some manufacturing processed used in the manufacture of plastics

A

extrusion
injection moulding
compression moulding

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7
Q

What was the first synthetic plastic and when was it produced?

A

Bakelite in 1907

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8
Q

What type of chemical bonding is prevalent in plastics?

A

covalent

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9
Q

What must an organic molecule contain?

A

carbon

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10
Q

What are the main types of hydrocarbons in crude oil?

A

Alkanes, Aromatics, cycloalkanes, alkenes, alkynes

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11
Q

Give an example of an alkane

A

methane, ethane, propane, butane, isobutane, pentane, hexane

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12
Q

Give an example of an aromatic

A

benzene, napthalene

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13
Q

Give an example of a cycloalkane

A

Cyclohexane, methyl cyclopentane

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14
Q

Give an example of alkene

A

ethylene, butene, isobutene

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15
Q

Give an example of an alkyne

A

actylene, butadienes

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16
Q

How are hydrocarbons refined?

A

fractional distillation

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17
Q

What are the monomers for PTFE, PVC and PP?

A

PTFE : 2 flourine per carbon
PVC: 2 hydrogen on one carbon and a hydrogen and a cholrine on the other
PP: 2 hydrogen on one carbon and a hydrogen and a methyl group on the other

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18
Q

What is the microstructure of a polymer like?

A

Can be chrystalline or amorphous
Have chrystalline and amorphous regions (semi chrystalline)
amount of chrystal phase changes properties

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19
Q

What are the 2 different classes of polymers

A

Thermoplastics

Thermosetting plastics

20
Q

What are the properties of a thermoplastic?

A

Become soft and melt when heated
Can be moulded into a new shape that is retained on cooling
Can be reheated and remouled many times
Have plastic memory

21
Q

What are the properties of a thermosetting plastic?

A
  • Set when first cooled down
  • will not soften when reheated
  • plastic will be destroyed before melted
22
Q

What allows the thermoplastics to be remoulded when heated?

A

They can be straight chain or branched chain, but they are held together by weak intermolecular bonding

23
Q

What are the effect of side chains on the properties of thermoplastics?

A

Side chains increase the distance between the main CC chain, this reduces the intermolecular attraction and results in different properties

24
Q

Give an example of how branches affect the properties of hydrocarbons

A

Low density polyethylene

High density poly ethylene (shorter branches)

25
Q

What makes a thermosetting plastic so strong?

A

They have networked covalent bonding and are cross linked with covalent bonding between chains

26
Q

Give an example of a thermosetting plastic

A

Bakelite, Phenolics, various epoxy resins and polyesters

27
Q

What is a polymer that is made form one or more polymer called?

A

A copolymer

28
Q

What are the different types of polymers?

A

Random
Alternating
Block
Graft

All of these give you different properties

29
Q

What are the general properties of polymers?

A
  1. Combustible
  2. Low melting point
  3. Low solubility in water
  4. High molecular
  5. Variable molecule size
  6. Low compressive strength
  7. Low stiffness
  8. High toughness
  9. Low density
  10. Durable
  11. Softens at low temperatures
  12. Low thermal conductivity
  13. Electrical insulators
  14. Low permeability
  15. Flexible
  16. Available in many forms
30
Q

How much plastic is produced per year worldwide?

A

~300 million tonnes

31
Q

How much is plastic consumption growing by in europe?

A

4% per year

32
Q

How much of the plastic produced per year is used in construction, and how much in packaging?

A

1/3 in packaging, 1/4 in construction

33
Q

What are some examples of high volume plastics?

A

Polyethylene (PE): containers , pipes, bags…
Polyvinylchloride (PVC): windowframes, pipes, flooring
Polypropylene (pp): film, chairs, fibres, car bumpers
Polystyrene (PS): packaging, thermal insulation, cups
Polyethylene tetrephthalate (PET): bottles, film, food packaging
Polyurethane (PU): adhesives, trainer soles, furniture foam
Acrylonitrile butadiene styrene (ABS): transparent all-weather sheet, electrical insulators

34
Q

What % of plastics are used in the construction sector?

A

23%

35
Q

Describe the process behind injection moulding?

A

Ram pushes plastic into a screw in a barrallel, where plastic granules are fed across heaters through a nozzle.

Molten plastic is fed into a mold, where it is then ejected and the part is formed

36
Q

What are the signature features of injection moulding?

A

An injection and ejection points

37
Q

What is the process behng compression molding?

A

Thermoset or thermoplastic charge is placed in mold

The mold has a plunger at the bottom which ejects it after molding

38
Q

How is plastic used in construction?

A

Plastics in construction are used for pipes and ducts. Nearly 30% are for insulation products, and the rest are for windows and floor coverings

39
Q

What plastic is used in landfills?

A

HDPE, it is used as a landfill liner

LDPE is used as a landfill cover

40
Q

What is the main plastic used in construction?

A

PVC

41
Q

What is bitumen produced from?

A

Crude oil during fractional distillation
It is the heaviest fraction with the highest boiling point >370C

Can also be found in natural deposits

42
Q

What kind of plastic is bitumen?

A

Thermoplastic

43
Q

What benefitial properties does bitumen have?

A

Waterproofing and adhesive

44
Q

What are the main chemical groups in bitumen

A

Asphaltenes and maltenes

exact composition depends on the crude oil and distiallation process

45
Q

What are the three different types of maltenes?

A

resins, aromatics and saturates

46
Q

Why is bitumen such a good binder for asphalt?

A

Bitumen can either actaas a straight forward binder, or its properties can be used depending on the ratio of aggregates to bitumen

Materials (13 decks)

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