How are low density polyethylene and high density polyethylene manufactured? Why do they differ in their densities?
Low density polyethylene : It is obtained by the polymerisation of ethene under high pressure of 1000 to 2000 atomspheres at a temperature of 350 K to 570 K in the presence of traces of dioxygen or a peroxide initiator. It is chemically inert and tough but flexible and a poor conductor of electricity.
High density polythene : It is formed when addition of 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 temperature of 333K to 343K and under a pressure of 6-7 atm. It is also chemically inert and more tougher and harder.
