production of polyethylene.docx
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Production of Polyethylene
There are two forms of polyethylene that can be produced via different production processes - high and low density.
Form Low density polyethylene (LDPE) High density polyethylene (HDPE)
Name of process - Ziegler-Natta process
Requirements
High pressure (1000 to 3000 atmospheres), high temperature (300°C), and an initiator (usually an organic peroxide)
Pressure of a few atmospheres, temperatures of about 60°C, and a catalyst
Polymerisation process
The peroxide initiator splits to form free radicals, which allow the initiation of the joining of ethylene monomers (the initiator is not a catalyst as it gets incorporated into the polymer)
The polymerisation occurs on the surface of the catalyst
Branching of polymer formed
Significant chain branching, meaning that polymer chains cannot pack closely together or in an orderly way
Unbranched polyethylene molecules that are able to pack closely together in an orderly fashion
Molecular weight of molecules formed
Up to 1 000 000 g/mol Up to 3 000 000 g/mol
Recycling symbol
The production processes for polyethylene
Structure of polyethylene
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