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CBSE Class 12-science Answered

as per exam point of view how we will write preparation of ldp and hdp
Asked by prkriti GUPTA | 22 Jul, 2012, 10:19: AM
answered-by-expert Expert Answer
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 | 25 Jul, 2012, 05:34: PM

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