help on production of polyethylene (2 Viewers)

[n a + a l i e]

?

huh? why wouldnt you have to know the two separate LDPE and HDPE methods, the initiator , propagation termination method only applies to one either LDPE or HDPE whereas the other uses a catalyst.?

 

[sikeveo]

You do have to know both methods, and LDPE and HDPE. HDPE uses the Ziegler-Natta catalyst. Whereas LDPE uses the 4 stage method.

There are actually 4 types of Polyethylene, but you only need to know 2:

* UHMWPE (ultra high molecular weight PE)
* HDPE (high density PE)
* LDPE (low density PE)
* LLDPE (linear low density PE, sometimes referred to as Medium Density PE, MDPE)

 

[Dreamerish*~]

You do have to know both methods, and LDPE and HDPE. HDPE uses the Ziegler-Natta catalyst. Whereas LDPE uses the 4 stage method.

There are actually 4 types of Polyethylene, but you only need to know 2:

* UHMWPE (ultra high molecular weight PE)
* HDPE (high density PE)
* LDPE (low density PE)
* LLDPE (linear low density PE, sometimes referred to as Medium Density PE, MDPE)

That's an awfully scary way of putting it.

I've never encountered a polymerisation question that required my answer to include anything involving Ziegler-Natta. I would say it's pretty safe to know just the LDPE process (that is, the initiaion-propagation-termination steps), however it is recommended that you learn a little bit extra just in case.

Just to sum up Z-N: the HDPE method is called the Ziegler-Natta process, and the catalyst is titanium (III) chloride and also trialkylaluminium compounds. It operates at relatively low pressures - a few atmospheres, and only around 60°C.

You can disregard all but the middle two of the bullet points. If a year 11 me was reading it, she would be falling off her chair in fright. One way to avoid unpleasant surprises involving information you never came across in class is to refer frequently to the syllabus.