chemistry - feedstock recycling problem

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pondering-soul
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From my textbook for AS level :
Feedstock Recycling
'Here, the plastics are heated to a temperature that will break the polymer bonds and produce monomers. These can then be used to make new plastics.

There are problems with recycling. Poly(propene), for example, is a thermoplastic polymer. This means that it will soften when heated so it can be melted and re-used. However, this can only be done a limited number of times because at each heating some of the chains break and become shorter thus degrading the plastic's properties. '

Ok, so it says that plastics are heated to break the polymer bonds and produce monomers. So, when poly(propene) is broken down, the chains break and become shorter degrading its properties... but isn't that what we want? Since we are breaking the polymer bonds to produce monomers? I don't get how this works, if anyone could explain I would be thankful.
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pondering-soul
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bump?
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pondering-soul
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(Original post by pondering-soul)
From my textbook for AS level :
Feedstock Recycling
'Here, the plastics are heated to a temperature that will break the polymer bonds and produce monomers. These can then be used to make new plastics.

There are problems with recycling. Poly(propene), for example, is a thermoplastic polymer. This means that it will soften when heated so it can be melted and re-used. However, this can only be done a limited number of times because at each heating some of the chains break and become shorter thus degrading the plastic's properties. '

Ok, so it says that plastics are heated to break the polymer bonds and produce monomers. So, when poly(propene) is broken down, the chains break and become shorter degrading its properties... but isn't that what we want? Since we are breaking the polymer bonds to produce monomers? I don't get how this works, if anyone could explain I would be thankful.
bump x2?
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Pigster
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(Original post by pondering-soul)
From my textbook for AS level :
Feedstock Recycling
'Here, the plastics are heated to a temperature that will break the polymer bonds and produce monomers. These can then be used to make new plastics.

There are problems with recycling. Poly(propene), for example, is a thermoplastic polymer. This means that it will soften when heated so it can be melted and re-used. However, this can only be done a limited number of times because at each heating some of the chains break and become shorter thus degrading the plastic's properties. '

Ok, so it says that plastics are heated to break the polymer bonds and produce monomers. So, when poly(propene) is broken down, the chains break and become shorter degrading its properties... but isn't that what we want? Since we are breaking the polymer bonds to produce monomers? I don't get how this works, if anyone could explain I would be thankful.
Recycling is the breakdown of a substance into a new form, e.g. melting down a glass bottle and making a new glass bottle.

You can recycle poly(propene) by melting something down and making a new poly(propene) thing.

If you crack a poly(propene) thing (which is what you are effectively doing when you melt it down too many time and break it into too short chains), then you can use that as organic feedstock, but you don't necessarily have to form poly(propene) once again.
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pondering-soul
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(Original post by Pigster)
Recycling is the breakdown of a substance into a new form, e.g. melting down a glass bottle and making a new glass bottle.

You can recycle poly(propene) by melting something down and making a new poly(propene) thing.

If you crack a poly(propene) thing (which is what you are effectively doing when you melt it down too many time and break it into too short chains), then you can use that as organic feedstock, but you don't necessarily have to form poly(propene) once again.
thanks man
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