If I’ve got a reactor containing PE-Polyethylene $(\ce{{C2}$H_\text{4})n$}$ (solid) and the rest is filled with nitrogen gas. The system is closed. Supposing we have an initial temperature of $30~\mathrm{°C}$ and gradually increase the temperature to $180~\mathrm{°C}$. We’ll observe a change in state of the PE, passing from solid to liquid, at this point the molecular structure is the same.

If temperature is increased beyond $250~\mathrm{°C}$ pyrolysis will occur on PE and syngas will be produced, at this point the gas molecules will have different structures compared to $(\ce{{C2}$H_\text{4})n$}$, thus "we’ll not observe" a change of phase from liquid to gas maintaining the same molecular structure. Gas molecules will nave n types of molecular structures.

  • Is it possible by varying PVT to have a change of phase, from liquid to gas, of PE and maintain the same molecular structure. Just like with water->vapor?
  • If this is not possible, why? what are the topics to study?
  • $\begingroup$ There are many types of polyethylene, melting point you added suggests HDPE, but I think your asking generally? $\endgroup$
    – Mithoron
    Jan 9 '15 at 13:56
  • $\begingroup$ It is generally assumed that polymers are unable to be in gaseous form. In fact, they even don't have a truly liquid and solid states, being in that respect similar to glasses: there is no strict border between liquid and solid states. Moreover, some kind of polymeric materials doesn't have liquid state either, being cross-linked. || However, deeply theoretically speaking, all compounds have non-zero, even if negligible vapor pressure, so at extremely low pressure polymers should be gaseos... except nobody was able to detect it. $\endgroup$
    – permeakra
    Jan 9 '15 at 14:25
  • $\begingroup$ @Mithoron yes, I'm talking in general about plastic polymers, the example was to make my question clear. $\endgroup$
    – Luther
    Jan 9 '15 at 14:48

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