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    Hi there,

    Basically, I'm trying to find out why is it that the production of HDPE has to be done at low pressure, and LDPE at high pressure. I can't find a thing on the internet. Can anyone shed any light?

    Cheers...

    J
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    (Original post by joshlemonsquash)
    Hi there,

    Basically, I'm trying to find out why is it that the production of HDPE has to be done at low pressure, and LDPE at high pressure. I can't find a thing on the internet. Can anyone shed any light?

    Cheers...

    J
    I suppose that high pressure brings the forming polymer chains into closer proximity and helps cross-linking...
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    Thanks for the reply!
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    I would assume it is because radical polymerisation for LDPE uses homogeneous reagents (eg oxygen or peroxide initiator with ethene), while HDPE is made using Ziegler-Natta catalysts which are normally heterogeneous. This means not only does pressure have a greater importance on the rate of reaction for LDPE (depending on the interaction of 2 gaseous molecules rather than one gaseous and one adsorbed onto a solid surface), but also the activation energy is lowered when making HDPE.

    Thus Ziegler-Natta catalysts in fluidised bed reactors work at lower pressures and temperatures than required for free-radical polymerisation.
 
 
 
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