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Chemistry 1 > Polymers > Flashcards

Polymers Flashcards

1
Q

What is a polymer?

A

A large molecule composed of many repeated subunits called monomers.

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2
Q

What is a monomer?

A

A monomer is a molecule that is able to bond in long chains and is a simple molecule.

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3
Q

What is a thermoplastic?

A

A polymer that can melted, reshaped when heated.

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4
Q

What is a thermosetting polymer?

A

When thermoset polymers are heated they do not melt but char. They cannot be reshaped so must be moulded during manufacture.

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5
Q

How can you produce polymers?

A

Addition polymerisation and condensation polymerization.

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6
Q

What is addition polymerisation?

A

Addition polymerisation is where small unsaturated monomers join up by opening the double bond allowing them to join up to form a long carbon chain.

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7
Q

How can addition polymerisation take place?

A

Monomer must have a double bond. Ethene can be modified by adding different functional groups to change the polymers properties.

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8
Q

What are the factors that affect the properties of polymers?

A
  • extent of branching
  • arrangement of side branches
  • cross linking of polymer chains
  • length of polymer chains
  • addition of plasticisers
  • additives
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9
Q

How does extent of branching effect properties of polymers?

A
  • Highly branched polymers: creates LDP because branches cause molecules to be spaced apart further and therefor have weaker dispersion forces.
  • Less branched polymers: creates HDP because molecules can come closer together
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10
Q

What are the properties of LDP?

A

Low density polymers are soft, flexible, transparent and has a waxy surface that repels water.

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11
Q

What are the properties of HDP? and how is HDP created?

A

Low pressure and low temperatures produce very few branches. This polymer is more rigid, stronger, opaque, it is slightly flexible and has a waxy outer layer that repels water.

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12
Q

What is a linear polymer?

A

When the main backbone of a polymer is unbranched,

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13
Q

What is an isotactic polymer?

A

When the side branches are arranged on the same side of a linear molecule. These polymers can pack together more closely. results in a HDP, rigid, tough and high softening temp.

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14
Q

What is an atactic polymer?

A

When branches occur at irregular points on the chignon both sides of a linear polymer. Chains of molecules int get close so LDP is formed.

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15
Q

What is cross linking?

A

Covalent bonds that are form between polymer chains.

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16
Q

What happens when a small amount of cross linking is introduced to a linear polymer?

A

An elastomer is formed.

17
Q

What happens when large amounts of cross linking is introduced to a linear polymer?

A

A thermoset polymer is formed and it can not be melted because the covalent bonds need extremely high temps to break and if this happened then all the other bonds would break so the molecule would inly burn.

18
Q

how would the degree of crystallinity effect a polymer?

A

The more crystalline a polymer chain is, that is the more regular arranged into lines, the polymer will be more hard, tensile and opaque.

19
Q

What factors effect crystallinity?

A
  • chain length
  • branching
  • interchain bonding
20
Q

What trend is evident in the length of polymer chains?

A

As chain length increases, strength, melting and boiling point also increase. Longer chains tend to get tangled and are less likely to slide over each other.

21
Q

Name 3 additives to polymers and explain their uses.

A
  • UV stabilisers which absorb Uv rays and prevent polymer from breaking
  • Flame retardants reduce polymer burning
  • dye adds colour and provides patterns
22
Q

What is a use of addition polymers?

A

Widely used in packaging industry.

23
Q

What is an elastomer?

A

.

24
Q

Why is rubber vulcanised?

A

.

25
Q

What is vulcanising?

A

.

26
Q

What are the advantages of using polymers?

A
  • dont corrode
  • less dense therefore lighter
  • relatively cheap to produce
  • good heat/ electricity insulators
  • can be moulded into any shape
27
Q

What are the disadvantages of using polymers?

A
  • use up finite resources
  • take a long time to decompose
  • take up space in land fill
  • pollution in ocean
  • when combusting, produces toxic gases
28
Q

How are some polymers recycled?

A

Shredded into flakes, washed to remove contaminants,. the flakes are then melted then chopped again.

29
Q

Why is LDP flexible and HDP is rigid?

A

LDP has weaker dispersion forces so its easier for molecules to slide over each other where as HDP has stronger dispersion forces so its molecules are held more strongly together and can slide over each other as easily.

30
Q

Why is the recycling of plastics desirable?

A

Reduces amount of valuable finite resources being used and reduces the amount of non biodegradable materials going to landfill.

Chemistry 1 (8 decks)

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