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A New Kind of Poly(ethene)
Poly(ethene) produced on Ziegler catalysts is quite different from ldpe. It has very little branching and is much more rigid, with a higher melting point. It is referred to as high density poly(ethene) or hdpe.

 

The chains pack tightly so it is denser. hdpe is rather brittle unless chains are long.

One of the techniques scientists use to identity materials is Infra-Red (IR) Spectroscopy.

As Idpe and hdpe are essentially the same compound (poly(ethene)), we would expect their IR Spectra to be very similar. Click here to see the IR Spectra of these materials.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

hdpe Properties

High Density poly(ethene)
  • Molecular mass several hundred to several millions (ultrahigh molecular mass poly(ethene)).
  • Branching low, 0.5 - 10 branches per 1000 carbons. Those with more branches are softer and more elastic.
  • Most branches are short
  • Crystallinity is between 40 and 80%
  • hdpe creeps under load
  • uhmwpe although completely unbranched crystallises poorly because of the very long chains which tangle