Polyethylene (1 Viewer)

[axlenatore]

Hey i just had some questions on the formation of high density polyethylene.
Firstly what catalyst is used in the Ziegler Natta process, and secondly in high density polyethylene do linear chains form, which bond together as a result of hydrogen bond, forming a csrytalline structure which gives it its density?
Ive found different explainations of this process in Excel, my text book, my notes and other students notes so any help would be appreciated.:uhhuh:

 

[brenton1987]

Ziegler Natta catalysts are usually titanium compounds and organoaluminium compounds.

There wont be any hydrogen bonding occuring between hydrocarbon chains.

 

[axlenatore]

thanks but what then holds the linear chains together into a crystalline structure?

 

[brenton1987]

Van der Waals forces hold the chains together. Because there is minimal branching the forces stronger than in LDPE.

 

[kooltrainer]

this naglar natter thing isnt in syllabus and thus wont be given extra mark for even if u wrote it in an exam

 

[Undermyskin]

This depends. Each marker has his own subjectivity. Any extra info relevant to the answer is accepted and awarded. As long as you can support your answers instead of trying to distract the marker because you don't know the right solution, you are in a high chance to get more marks.

What's Van de Waals force? A type of intermolecular forces?

 

[tacogym27101990]

its another name for dispersion forces i think

 

[kooltrainer]

look, theres a set criteria from which the hsc markers would give their marks accordingly. I dun think there'll be a criterion.
> Has written about naglar natter I Mark

Or
> Demonstrate extensive knowledge 1 Mark

For HDPE, u just need to know it is made in addition reaction and relate its property to its use. Other than that, it'll be useless information

 

[Undermyskin]

Zeigler Natta, mind you.

That's what I said: the subjectivity element. Markers are allowed to award extra marks for students with broader and more extensive knowledge. This is science, not the memorization competition. In addition, it's said that if the students answer more than the scope of a question (and must be correct, apparently), their papers are marked with this additional info.

 

[tommykins]

回复: Polyethylene

Hey i just had some questions on the formation of high density polyethylene.
Firstly what catalyst is used in the Ziegler Natta process, and secondly in high density polyethylene do linear chains form, which bond together as a result of hydrogen bond, forming a csrytalline structure which gives it its density?

Titanium Chloride is what I have in my notes (TiCl4) and is produced under low pressure where ethene monomers add to the growing polymer on the surface of the catalyst.

 

[axlenatore]

this naglar natter thing isnt in syllabus and thus wont be given extra mark for even if u wrote it in an exam

The syllabus dot point is http://community.boredofstudies.org/outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer, and since there is two type of pothethylene (HDPE and LDPE) and HDPE is only produced by the Neigler Natta process you would have to assume that it is part of the course otherwise you would only have minimal knowledge on this aspect.

 

[tommykins]

回复: Re: Polyethylene

The syllabus dot point is http://community.boredofstudies.org/outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer, and since there is two type of pothethylene (HDPE and LDPE) and HDPE is only produced by the Neigler Natta process you would have to assume that it is part of the course otherwise you would only have minimal knowledge on this aspect.

I never learnt the name of the process, just how it worked.