a version of the molecule where there are many branches from the polymer chains resulting in a softer material with a low melting point
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What are the typical uses of LDPE?
packaging and electrical insulation
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What is high density ploy(ethene)?
a version of the molecule with little branching so the chains can get closer together, resulting in a stronger and more rigid material with a higher melting point
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How is HDPE formed?
using a Ziegler catalyst
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Why is PVC stronger than poly(ethene)?
the chlorine provies a permanent dipole which creates stronger intermolecular forces, PVC is brittle though as the big chlorine atoms mean that the chains cannot move past each other
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What are the three types of addition polymers?
Isotactic, Syndiotactic and Atactic
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What is an Isotatic addition polymer?
the functional groups are evenly spaced on the smae side of the molecule
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What is a Syndiotatic addition polymer?
the functional groups are evenly spaced and alternate between sides
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What is an Atatic addition polymer?
the functional groups are randomly positions
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How can a polymer be made stronger?
by either adding an electronegative atom to strengthen the intermolecular forces of by increasing the number of cross linkages (eg using sulphur to create vulcanised rubber)
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What mechanism and conditions does polymerisation use?
free radical mechanism, with high temperature, high pressure and a catalyst
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How is the repeating unit shown?
using square brackets and a small n to show a large number of repeats
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Give some examples of common addition polymers and their uses
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