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Question
Low density polythene and high density polythene, both are polymers of ethene but there is marked difference in their properties. Explain.
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Solution
| LDP | HDP |
| 1. It is obtained by the polymerisation 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). | 1. 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. |
| 2. (LDP) is obtained through the free radical addition and H-atom abstraction. It has highly branched structure. | 2. (HDP) thus produced, consists of linear molecules as shown below and has a high density due to close packing. |
| 3. Low-density polythene is chemically inert and tough but flexible and a poor conductor of electricity. | 3. It is also chemically inert and more tough and hard. |
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