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CBSE - XII Science - Chemistry - Polymers

as per exam point of view how we will write preparation of ldp and hdp

Asked by prkriti GUPTA 22nd July 2012, 10:19 AM
Answered by Expert


Low density polythene: It is obtained by the polymerization of ethene under high pressure of 1000 to 2000 atmospheres at a temperature of 350 K to 570 K in the presence of traces of dioxygen or a peroxide initiator (catalyst). The low density polythene (LDP) obtained through the free radical addition and H-atom abstraction has highly branched structure.


High density polythene: It is formed when addition polymerisation of ethene takes place in a hydrocarbon solvent in the presence of a catalyst such as triethylaluminium and titanium tetrachloride (Ziegler-Natta catalyst) at a temperature of 333 K to 343 K and under a pressure of 6-7 atmospheres. High density polythene (HDP) thus produced, consists of linear molecules and has a high density due to close packing. 

Answered by Expert 25th July 2012, 5:34 PM

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