addition polymerisation (1 Viewer)

[oranGez]

identify polyethylene as an addition polymer and explain the meaning of this term

outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer


putting these two dotpoints together, it sounds like polyethylene is made by addition polymerisation.. but all my textbooks and notes dont mention it, they just say the steps without actually naming the process..im really confused (and obviously a lil dense).. is polyethylene produced by the process of addition polymerisation or not =[ ..

 

[Trefoil]

You can tell by inspection.

You know what polymerisation is, yes? You know what ethylene is?

The monomer in question is CH₂=CH₂

If if you were to crudely "join" some of these monomers together, there's absolutely no way water could be eliminated, and since you know polyethylene exists, the only conclusion that remains is that ethylene undergoes addition polyermisation to form polyethylene.

Example:

CH₂=CH₂ + CH₂=CH₂ + CH₂=CH₂
Goes to:
-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-

It is addition because the double bond is broken, thus forming two free "spots". These free spots "add" with free spots of other ethylene monomers with their double bond broken.

 

[mushroom_head]

yep! polyethylene is definitely made by addition polymerisation

 

[xiao1985]

addition polymer: the formation of a polymer by breakin of a double bond and form covalent bond with adjacent monomers...

in addition, note the name of the process mentioned above: gas phase process,
condition: 1000-3000 atm, 500k, initiator

may also mention zeigler natta process, formin HDPE
60C, 2-3 atm, organic catalyst, mixture of titanium(III) chloride + trialkyl aluminium

 

[nit]

Hmm, yeh, some of those conditions are debatable, Xiao . There was a discussion on the exact conditions a couple of months ago, and there was no real conclusion reached as such, so I don't think they're terribly central. Apart from that, just for a sake of completion, the Zeigler-Natta catalyst incorporates titanium (III) chloride and triethyl aluminium.

Addition polymerisation can also be generally thought of as that polymerisation process in which every monomer atom is conserved and thus present in the final polymer, and thats obviously linked to the double bond - the fact that it cleaves homolytically allows for the extra bonding capacity of the double bond carbons, meaning that no atoms of the growing polymer chain or the monomers need to be eliminated.