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what are LDPE and HDPE? HOW are they prepared?

LDPE is low density polyethylene. It is a thermoplastic which is made from ethylene.

Its preparation is carried out by heating ethylene to 350-570K under a pressure between 1000-2000 atmospheres in presence of traces of oxygen or peroxide which helps in carrying the free radical mechanism of the reaction.

HDPE is high density polyethylene which is prepared by co-ordination polymerization, which occurs through the formation of intermediate complexes, of ethene. Here, ethene is heated to 333-343 K under a pressure of 6-7 atmospheres. The catalysts used in this reaction are Ziegler- Natta catalyst.

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LDPE - low desity polythene . 

they are obtained by polymerisation of ethene under high pressure of 1000-2000 atmosphere and at a temperature of 350 - 570 K  in presence of traces of dioxygen or peroxide .it is chemically inert tough but flexible 

HDPE  - high density polythene 

they are obtained by polymerisation of ethene under low pressure .the catalyst used here is zeigler natta catalyst .

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