sikeveo said:
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.
![Stick Out Tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
One way to avoid unpleasant surprises involving information you never came across in class is to refer frequently to the syllabus.