Chemistry C2 2.5 The properties of polymers.

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What do the properties of polymers depend on?
The monomers used to make them and the conditions we use to carry out the reaction..
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What can changing reaction conditions do?
It can also change the properties of the polymer that is produced.
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What ar thermosoftening polymers?
Polymers that soften or melt easily when heated.
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What are thermosetting polymers?
Polymers that do not soften or melt when heated.
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What is poly(propene) made from and what is its properties?
It is made from propene and softens at a higher temperature than poly(ethene) which is made from ethene.
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What is the difference between low density (LD) poly(ethene) and high density poly(ethene)?
They are made using different catalysts and different reaction conditions, HD poly(ethene) has a higher softening temperature and is stronger than LD poly(ethene).
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What is poly(ethene) an example of?
A thermosoftening polymer.
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What is the structure of poly(ethene) and what are its properties?
It is made up of individual polymer chains that are tangled together. When it is heated it becomes soft and hardens again when it cools, this means it can be heated to mould it into shape and it can be remoulded by heating it again.
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Apart from thermosoftening polymers, what other polymers are there and what is their structure and properties?
Thermosetting polymers, they do not melt or soften when we heat them. They set hard when they are first moulded because strong covalent bonds form cross-links between their polymer chains, the strong bonds hold the polymer chains in position.
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What happens when a thermosoftening polymer is heated?
In thermosoftening polymers the forces between the polymer chains are weak, these weak intermolecular forces are broken when heated and the polymer becomes soft. When it cools down the intermolecular forces bring the molecules back together again.
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Why do LD and HD poly(ethene) have different properties?
They are made using different reaction conditions; they have different structures or differently shaped molecules.
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What is the min difference in the structures of thermosoftening and thermosetting polymers?
Thermosoftening polymers have no cross-links or no covalent bonds between the polymer chains, thermosetting polymers have cross-links.
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What allows thermosoftening polymers to be remoulded?
The weak intermolecular forces between the chains (are overcome by heat).
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**YOU SHOULD BE ABLE TO RECOGNISE THE TYPE OF POLYMER FROM A DIAGRAM OF ITS STRUCTURE OR A DESCRIPTION OF ITS PROPERTIES**
**THERMOSETTING POLYMERS HAVE COVALENT BONDS LINKING THE CHAINS AND DO NOT SOFTEN WHEN HEATED**
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Other cards in this set

Card 2

Front

What can changing reaction conditions do?

Back

It can also change the properties of the polymer that is produced.

Card 3

Front

What ar thermosoftening polymers?

Back

Preview of the front of card 3

Card 4

Front

What are thermosetting polymers?

Back

Preview of the front of card 4

Card 5

Front

What is poly(propene) made from and what is its properties?

Back

Preview of the front of card 5
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